TAKAYUKI ISHIDA
| Department of Engineering Science | Professor |
| Cluster III (Fundamental Science and Engineering) | Professor |
Researcher Information
Field Of Study
Career
Educational Background
Research Activity Information
Award
- Jul. 2017
東北大学金属材料研究所強磁場センター
ヘテロスピン希土類錯化合物に見られる磁気異方性の研究
Selected Topics 2016 HFLSM-IMR - Feb. 2017
American Chemical Society
USA
ACS Editors' Choice, T. Kanetomo;T. Kihara;A. Miyake;A. Matsuo;M. Tokunaga;K. Kindo;H. Nojiri;T. Ishida
Official journal, United States - Feb. 2016
The Japan Chemical Society
Japan
BCSJ Award, Yumi Ida;Hiroyuki Nojiri;Takayuki Ishida
Official journal, Japan - Nov. 2015
日本学術振興会
平成27年度「科研費」審査委員表彰
科研費審査委員表彰
Publisher - Aug. 2008
東北大学金属材料研究所
Research Highlights 2008 IMR - Jun. 2004
日本化学会欧文誌
Selected Paper (BCSJ), N. Takagami;T. Ishida;T. Nogami
Official journal, Japan
Paper
- Diamagnetic Precursor to Biradical by Means of a Thermal Trigger: A Head-to-Tail (N–O)2 Four-Membered Ring Formed in Naphthalene-1,8-diyl Bis(tert-butyl Nitroxide)
Rika Uesugi; Rina Takano; Takayuki Ishida
Corresponding, The Journal of Organic Chemistry (Supplementary Journal Cover), 89, Oct. 2024, Peer-reviwed
English - First TPymT-Ln Complexes (TPymT = 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine; Ln = Eu, Gd, Tb, Dy): Solvothermal Synthesis, Structure, Magnetic and Photoluminescent Properties
Burak Ay; Rina Takano; Takayuki Ishida
Corresponding, Solid State Sciences, Elsevier BV, 157, 107723/1-11, Oct. 2024, Peer-reviwed
Scientific journal, English - Temperature-scan-rate dependent SCO hysteresis found in a tetramethylphosphonium tripodal ferrate(II) salt
Masaru Yamasaki; Yoshimasa Noguchi; Takayuki Ishida
Corresponding, Inorganica Chimica Acta, Elsevier BV, 569, 122112/1-7, May 2024, Peer-reviwed
Scientific journal, English - Biradical pincers involving two phenylene, biphenylene or terphenylene arms: Evidence for approach of two terminal nitroxides
R. Uesugi; R. Takano; T. Ishida
Corresponding, Tetrahedron, 156, 133929/1-7, Mar. 2024, Peer-reviwed
English - A Triplet/Singlet Ground-State Switch via the Steric Inhibition of Conjugation in 4,6-Bis(trifluoromethyl)-1,3-phenylene Bisnitroxide
N. Haga; T. Ishida
Molecules, MDPI AG, 29, 70/1-14, 21 Dec. 2023, Peer-reviwed, Ground triplet 4,6-bis(trifluoromethyl)-1,3-phenylene bis(tert-butyl nitroxide) (TF2PBN) reacted with [Y(hfac)3(H2O)2] (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate), affording a doubly hydrogen-bonded adduct [Y(hfac)3(H2O)2(TF2PBN)]. The biradical was recovered from the adduct through recrystallization. Crystallographic analysis indicates that the torsion angles (|θ| ≤ 90°) between the benzene ring and nitroxide groups were 74.9 and 84.8° in the adduct, which are larger than those of the starting material TF2PBN. Steric congestion due to o-trifluoromethyl groups gives rise to the reduction of π-conjugation. Two hydrogen bonds enhance this deformation. Susceptometry of the adduct indicates a ground singlet with 2J/kB = −128(2) K, where 2J corresponds to the singlet–triplet gap. The observed magneto-structure relation is qualitatively consistent with Rajca’s pioneering work. A density functional theory calculation at the UB3LYP/6-311+G(2d,p) level using the atomic coordinates determined provided a result of 2J/kB = −162.3 K for the adduct, whilst the corresponding calculation on intact TF2PBN provided +87.2 K. After a comparison among a few known compounds, the 2J vs. |θ| plot shows a negative slope with a critical torsion of 65(3)°. The ferro- and antiferromagnetic coupling contributions are balanced in TF2PBN, being responsible for ground-state interconversion by means of small structural perturbation like hydrogen bonds.
Scientific journal, English - Continuous condensed triplet accumulation for irradiance-induced anticounterfeit afterglow
E. H. Badriyah; K. Hayashi; B. Sk; R. Takano; T. Ishida; S. Hirata
Advanced Science, 10, 2304374/1-11, Oct. 2023, Peer-reviwed
Scientific journal, English - Metal-organodiphosphonate chemistry: Hydrothermal syntheses and structures of two novel copper(II) coordination polymers with o-xylylenediphosphonic acid and 4,4'-bipyridine ligands
B. Ay; R. Takano; T. Ishida
Corresponding, Bulletin of the Chemical Society of Japan, 96, 1129-1138, Oct. 2023, Peer-reviwed
Scientific journal, English - Bilayered Lanthanide Squarate Hydrates (Ln = Eu to Lu) and Magnetization Reversal Barriers 21 K for Ln = Tm and 57 K for Yb
R. Takano; K. Masuda; K. Cho; Y. Kitagawa; T. Ishida
Last, Dalton Transaction (Journal Inside Front Cover), RSC, 52, 8873-8882, May 2023, Peer-reviwed
Scientific journal, English - Tricopper(II) Bis(2-((hydrogen Phosphonato)methyl)benzylphosphonate) as a Layered Oxo-bridged Copper(II) Coordination Polymer: Synthesis, Structure, Magnetic Property, and Catalytic Activity
B. Ay; R. Takano; T. Ishida; E. Yildiz
Polyhedron, Elsevier, 226, 116038/1-7, Oct. 2022, Peer-reviwed
Scientific journal, English - Synthesis, Crystal Structure, and Luminescent Property of a Three-Dimensional Coordination Polymer from Europium(III) Carbonate Hemioxalate Hydrate
R. Takano; T. Ishida; B. Ay
CrystEngComm, RSC, 24, 7786-7792, Sep. 2022, Peer-reviwed
Scientific journal, English - Ferromagnetic 2p-2p and 4f-2p Couplings in a Macrocycle from Two Biradicals and Two Gadolinium(III) Ions
S. Ito; T. Yoshitake; T. Ishida
Molecules, mdpi, 27, 4930/1-14, Aug. 2022, Peer-reviwed
Scientific journal, English - Rare-Earth (RE = Y, Gd, Tb, Dy, Ho, and Er) Chains Bridged with a Triplet Biradical and Magnetic Hysteresis Recorded for RE = Tb
S. Ito; R. Takano; S.-i. Hatanaka; T. Ishida
Inorganic Chemistry (Journal Inside Front Cover), ACS, 61, 10619-10623, Jul. 2022, Peer-reviwed
Scientific journal, English - Pincer-type Bisnitroxide Radicals Involving Tetramethylenedioxy and o-Xylylenedioxy Bridges
Y. Yamaguchi; R. Takano; T. Ishida
Tetrahedron Letters (Journal Front Cover), Elsevier, 99, 153841/1-5, Jun. 2022, Peer-reviwed
Scientific journal, English - Structures and Magnetic Properties of Carbonato-Bridged Hexanuclear NiII4LnIII2 (Ln = Gd, Tb, Dy) Complexes Formed by Atmospheric Carbon Dioxide Fixation in the Absence of an External Base
S. Maity; T. K. Ghosh; S. Ito; P. Bhunia; T. Ishida; A. Ghosh
Crystal Growth & Design, ACS, 22, 4332-4342, Jun. 2022, Peer-reviwed
Scientific journal, English - Lanthanide Induced Variability in Localised CoII Geometries of Four Triangular L3Co3IILnIII Complexes
T. N. Dais; R. Takano; T. Ishida; P. G. Plieger
RSC Advances, RSC, 12, 4828-4835, Mar. 2022, Peer-reviwed
Scientific journal, English - [Tb4(OH)4]-Cuboid Complex Dianion Stabilized with Six Carboxylate Bridges and Four Diketonate Caps
Y. Yamaguchi; T. Ishida
Crystals, mdpi, 12, 402/1-7, Mar. 2022, Peer-reviwed
Scientific journal, English - Metallocyclic CuII-LnIII Single-Molecule Magnets from the Self-Assembly of 1,4-Diformylnaphthalene-2,3-diol
T. N. Dais; R. Takano; Y. Yamaguchi; T. Ishida; P. G. Plieger
ACS Omega, ACS, 7, 5537-5546, Feb. 2022, Peer-reviwed
Scientific journal, English - Self-Assembly of Non-Macrocyclic Triangular Ni3Ln Clusters
T. N. Dais; R. Takano; T. Ishida; P. G. Plieger
Dalton Transactions, RSC, 51, 1446-1453, Jan. 2022, Peer-reviwed
Scientific journal, English - Polymeric Terbium(III) Squarate Hydrate as a Luminescent Magnet
R. Takano; T. Ishida
Crystals, mdpi, 11, 1221/1-9, 2021, Peer-reviwed
Scientific journal, English - Strong Antiferromagnetic Interaction in a Gadolinium(III) Complex with Methoxy-TEMPO Radical: A Relation between the Coupling and the Gd-O-N Angle
T. Nakamura; T. Kanetomo; T. Ishida
Inorganic Chemistry, American Chemical Society (ACS), 60, 2, 535-539, 2021, Peer-reviwed
Scientific journal, English - Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds
T. Ishida; S. Ito; Y. Homma; Y. Kyoden
Inorganics (Journal Front Cover), MDPI, 9, 10/1-28, 2021, Peer-reviwed, Invited
Scientific journal, English - SMM Behaviour of Heterometallic Dinuclear CuIILnIII (Ln = Tb and Dy) Complexes Derived from N2O3 Donor Unsymmetrical Ligands
S. Maity; P. Bhunia; K. Ichihashi; T. Ishida; A. Ghosh
New Journal of Chemistry, RSC, 44, 6197-6205, 2020, Peer-reviwed
Scientific journal, English - An Indication of Spin-Transition Accompanied by Order-Disorder Structural Transformation in [Ni(phpyNO)2(NCS)2] (phpyNO = tert-Butyl 5-Phenyl-2-pyridyl Nitroxide)
Y. Kyoden; T. Ishida
RSC Advances, RSC, 10, 16009-16015, 2020, Peer-reviwed
Scientific journal, English - Odd-Even Effect on the Spin-Crossover Temperature in Iron(II) Complex Series Involving an Alkylated or Acyloxylated Tripodal Ligand
A. Kashiro; W. Kohno; T. Ishida
Inorganic Chemistry, ACS, 59, 10163-10171, 2020, Peer-reviwed
Scientific journal, English - Practically Diamagnetic Macrocycle Consisting of Nickel-Biradical Heterospins with the Largest Out-of-Plane Torsion at Coordination Bonds
S. Ito; T. Ishida
Chemistry Letters, 日本化学会, 49, 1062-1065, 2020, Peer-reviwed
Scientific journal, English - 2,7-Di-tert-butyl-9,9’(10H,10’H)-spirobiacridine-10,10’-dioxyl as a Ground Triplet Biradical: the Role of tert-Butylation
K. Ichihashi; T. Kanetomo; M. Enomoto; T. Ishida
Tetrahedron Letters, Elsevier, 61, 43, 152428/1-5, 2020, Peer-reviwed, © 2020 Elsevier Ltd The synthesis of a doubly tert-butylated spirobiradical, 2,7-di-tert-butyl-9,9′(10H,10′H)-spirobiacridine-10,10′-dioxyl is reported. The X-ray diffraction study clarified that the two dihydroacridine skeletons were fused at the sp3-carbon atom affording a cruciform structure. The frozen-solution electron spin resonance spectrum showed a typical zero-field-splitting pattern. The magnetic study revealed the presence of an intramolecular ferromagnetic interaction with 2J/kB = +22.3(5) K. The density-functional-theory calculation results are entirely consistent with the experimental results. After comparison with the known unsubstituted spirobiradical, we can conclude that tert-butylation is a useful method to reduce the intermolecular interaction without breaking the degeneracy of the singly occupied molecular orbitals.
Scientific journal, English - A Hidden Coordination-Bond Torsional Deformation as a Sign of Possible Spin Transition in Nickel(II)-Bis(nitroxide) Compounds
Y. Kyoden; T. Ishida
Molecules, mdpi, 25, 3790/1-11, 2020, Peer-reviwed
Scientific journal, English - Modulating the Ground State, Stability and Charge Transport in OFETs of Biradicaloid Hexahydro-diindenopyrene Derivatives and a Proposed Method to Estimate the Biradical Character
T. Jousselin-Oba; M. Mamada; A. Okazawa; J. Marrot; T. Ishida; C. Adachi; A. Yassar; M. Frigoli
Chemical Science, Royal Society of Chemistry (RSC), 11, 44, 12194-12205, 2020, Peer-reviwed,Biradicaloid HDIP derivatives show that the Δ
E S–T gap does not follow the reverse trend of the biradical character but depends more on the delocalization of the radical centres at the outer rings.
Scientific journal, English - Methoxy-TEMPO and Gadolinium(III) Complex Showing the Strongest Antiferromagnetic Interaction. A Relation between the Coupling and Gd-O-N Angle
T. Nakamura; T. Ishida
Inorganic Chemistry, 99, 9999, 2020, Peer-reviwed
Scientific journal, English - Effects of ZnO Nanoparticles on the Antifungal Performance of Fe3O4/ZnO Nanocomposites Prepared from Natural Sand
A. Taufiq; H. N. Ulya; C. I. Yogihati; Sunaryono; N. Hidayat; N. Mufti; Masruroh; S. Soda; T. Ishida
Advances in Natural Sciences: Nanoscience and Nanotechnology, IOPscience, 11, 045004/1-10, 2020, Peer-reviwed
Scientific journal, English - 結晶固体中で有機分子は動く：緩やかな構造転移とスピン転移/クロスオーバー
嘉代 敦; 京田幸也; 岡澤 厚; 石田尚行
有機合成化学協会誌, 有機合成化学協会, 77, 684-695, Jul. 2019, Peer-reviwed, Invited
Scientific journal, Japanese - A Series of CuII−LnIII Complexes of an N2O3 Donor Asymmetric Ligand and a Possible CuII−TbIII SMM Candidate in No Bias Field
P. Mahapatra; N. Koizumi; T. Kanetomo; T. Ishida; A. Ghosh
New Journal of Chemistry, RSC, 43, 2, 634-643, 2019, Peer-reviwed, © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. A new series of four heterometallic Cu(ii)-Ln(iii) complexes [where Ln = Tb (1Tb), Dy (2Dy), Ho (3Ho) or Er (4Er)] has been synthesized using a Cu(ii) metalloligand of an N2O3-donor asymmetric ligand H2L (H2L = N-α-methylsalicylidene-N′-3-methoxysalicylidene-1,3-propanediamine) and structurally characterized. All these complexes are isostructural and consist of dinuclear [ (CuL)Ln(NO3)3] units. The Ln(iii) ions are nona-coordinated and the Cu(ii) ions are tetra-coordinated with distorted square planar geometry in all the complexes. The DC magnetic susceptibility and field dependent magnetization measurements reveal that the Cu(ii) and Ln(iii) centres are ferromagnetically coupled in complexes 1Tb and 2Dy. In the AC magnetic susceptibility measurements at zero bias field, 1Tb exhibits an appreciable slow magnetic reorientation below 10 K with an effective energy barrier of approximately 17 K. Complex 3Ho shows a slight increase in out-of-phase susceptibility below 4 K. With an applied DC field of 2000 Oe, both 1Tb and 2Dy display slow magnetic reorientation with effective energy barriers of 28.5(5) and 53(2) K, respectively.
Scientific journal, English - Moving Molecules in Crystalline Solids: Gradual Structure Transition and Spin Transition/Crossover
T. Ishida
IOP Conference Series: Materials Science and Engineering, Institute of Physics, 515, 012001/1-16, 2019, Peer-reviwed, Invited
International conference proceedings, English - Synthetic Investigation for Spiro-Junctioned Biradical Compounds
K. Ichihashi; M. Okamura; T. Kanetomo; T. Ishida
AIP Conference Proceedings, AIP, 2067, 020011/1-5, 2019, Peer-reviwed, © 2019 Author(s). Biradical compounds are expected as promising building blocks for molecular magnetic materials, especially when they have a ground triplet state. We focused on spiro-junctioned D2d biradicals, 9,9'(10H,10H')-spirobiacridine-10,10'-dioxyls. tert-Butylation would suppress intermolecular interaction and facilitate analysis on the intramolecular exchange coupling. During attempted preparation of a precursory diamine 2,2',7,7'-tetra-tert-butyl-9,9'(10H,10'H)-spirobiacridine, 2,7-di-tert-butyl-9-{3-tert-butyl-6-(4-tert-butylphenylamino)phenyl}acridine was isolated as an isomeric byproduct and characterized by means of spectroscopic methods including 2D NMR. Fast aromatization is assumed to occur before intramolecular Friedel-Crafts cyclization.
International conference proceedings, English - Biphenyl-Hinged Bisnitroxide Biradicals toward Intramolecular Para- and Diamagnetic Switching
M. Arai; T. Ishida
AIP Conference Proceedings, AIP, 2067, 020008/1-7, 2019, Peer-reviwed
International conference proceedings, English - Structures and Magnetic Properties of Lanthanide Complexes Involving Ground Triplet Bisnitroxide Radicals
H. Sekine; T. Ishida
AIP Conference Proceedings, AIP, 2067, 020003/1-3, 2019, Peer-reviwed
International conference proceedings, English - Iron(II) and 1,1,1-Tris(2-pyridyl)nonadecane Complex Showing an Order-Disorder-Type Structural Transition and Spin-Crossover Synchronized over Both Conformers
A. Kashiro; K. Some; Y. Kobayashi; T. Ishida
Inorganic Chemistry, ACS, 58, 7672-7676, 2019, Peer-reviwed
Scientific journal, English - Ground Triplet Spirobiradical: 2,2’,7,7’-tetra(tert-butyl)-9,9’(10H,10’H)-spirobiacridine-10,10’- dioxyl
T. Kanetomo; K. Ichihashi; M. Enomoto; T. Ishida
Organic Letters (Journal Inside Front Cover), ACS, 21, 11, 3906-3912, 2019, Peer-reviwed, © 2019 American Chemical Society. A new spirobiradical, 2,2′,7,7′-tetra(tert-butyl)-9,9′(10H,10′H)-spirobiacridine-10,10′-dioxyl, was prepared. The crystallographic analysis clarified the D2d molecular structure, suggesting the degeneracy of SOMOs. The magnetic study revealed that intramolecular ferromagnetic coupling was operative with 2J/kB = +23(1) K. To the best of our knowledge, the ferromagnetic coupling parameter is the largest ever reported for a paramagnetic spiro compound.
Scientific journal, English - High-Spin and Incomplete Spin-Crossover Polymorphs in Doubly Chelated [Ni(L)2Br2] (L = tert-Butyl 5-Phenyl-2-pyridyl Nitroxide)
Y. Kyoden; Y. Homma; T. Ishida
Inorganic Chemistry, ACS, 58, 10743-10755, 2019, Peer-reviwed
Scientific journal, English - Structure-fluorescence relationship of push-pull 2-phenylbenzothiazole derivatives designed based on the firefly light-emitter
Tomoya Fujikawa; Takuya Uehara; Minoru Yamaji; Takuya Kanetomo; Takayuki Ishida; Shojiro Maki; Takashi Hirano
Tetrahedron Letters, Elsevier Ltd, 59, 14, 1431-1434, 04 Apr. 2018, Peer-reviwed, 6-Dimethylamino-2-phenylbenzothiazole (1a) mimicking the firefly oxyluciferin structure and the derivatives with an electron-withdrawing substituent on the phenyl group were prepared, and their fluorescence properties were investigated in various solvents. 1a showed solvatochromic fluorescence with good fluorescence quantum yields (Φf >
0.8). The introduction of an electron-withdrawing group led to a red-shift of the emission maximum. In particular, the derivatives with the 2,2-dicyanoethenyl and (1,3-dihydro-1,3-dioxo-2H-inden-2-ylidene)methyl groups showed near-infrared fluorescence in chloroform. In addition, the derivative with the phenylimine moiety showed efficient solid-state fluorescence, resulted from a molecular arrangement inhibiting intermolecular interactions for quenching the fluorescence state in crystals.
Scientific journal, English - Cobalt(II) terpyridin-4′-yl nitroxide complex as an exchange-coupled spin-crossover material
Akihiro Ondo; Takayuki Ishida
Crystals, MDPI AG, 8, 4, 155/1-12, 01 Apr. 2018, Peer-reviwed, Spin-crossover (SCO) was studied in [Co(L)2](CF3SO3)2, where L stands for diamagnetic 2,2′:6′,2′′-terpyridine (tpy) and its paramagnetic derivative, 4′-{4-tert-butyl(N-oxy)aminophenyl}-substituted tpy (tpyphNO). The X-ray crystallographic analysis clarified the Co-N bond length change (Δd) in high- and low-temperature structures
Δdcentral = 0.12 and Δddistal = 0.05 Å between 90 and 400 K for L = tpy and Δdcentral = 0.11 and Δddistal = 0.06 Å between 90 and 300 K for L = tpyphNO. The low- and high-temperature structures can be assigned to approximate low- and high-spin states, respectively. The magnetic susceptibility measurements revealed that the χmT value of [Co(tpyphNO)2](CF3SO3)2 had a bias from that of [Co(tpy)2](CF3SO3)2 by the contribution of the two radical spins. The tpy compound showed a gradual SCO around 260 K and on cooling the χmT value displayed a plateau down to 2 K. On the other hand, the tpyphNO compound showed a relatively abrupt SCO at ca. 140 K together with a second decrease of the χmT value on further cooling below ca. 20 K. From the second decrease, Co-nitroxide exchange coupling was characterized as antiferromagnetic with 2JCo-rad/kB = –3.00(6) K in the spin-Hamiltonian H = –2JCo-rad(SCo·Srad1 + SCo·Srad2). The magnetic moment apparently switches double-stepwise as 1 μB ⇄ 3 μB ⇄ 5 μB by temperature stimulus.
Scientific journal, English - A New S = 0 ⇆ S = 2 "spin-Crossover" Scenario Found in a Nickel(II) Bis(nitroxide) System
Yuta Homma; Takayuki Ishida
Chemistry of Materials, American Chemical Society, 30, 6, 1835-1838, 27 Mar. 2018, Peer-reviwed
Scientific journal, English - Unexpected complexes from meta -phenylene bis(tert -butyl nitroxides) and gadolinium(III) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate
Hiroyasu Sekine; Takayuki Ishida
AIP Conference Proceedings, American Institute of Physics Inc., 1929, 020022/1-6, 22 Jan. 2018, Peer-reviwed, Coordination reaction of the stable ground triplet biradical biphenyl-3,5-diyl bis(tert-butyl nitroxide) and [Gd(hfac)3(H2O)2] unexpectedly gave complexes containing a dimerized diamagnetic ligand via a [3+3] cycloaddition of the benzene rings (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate). To avoid such dimerization, we introduced a bulkier substituent into the ligand
namely, a new ground triplet biradical 5-mesityl-1,3-phenylene bis(tert-butyl nitroxide) was applied to this complexation scheme. However, an unexpected complex was again obtained in a different way, and the magnetic study revealed that the novel ligand involved was diamagnetic. The crystallographic analysis of the product clarified isomerization from the paramagnetic ligand to a diamagnetic N-tert-butylaminoquinone imine N-oxide ligand as a result of disproportionation from two open-shell nitroxide groups to closed-shell groups, an amine and a nitrone. The present paper reports the first structural evidence for a diamagnetic isomer of m-phenylene-bridged bisnitroxde compounds.
International conference proceedings, English - Substituent effect in spin-crossover behavior of iron(II)-Ar-pybox complexes (Ar-pybox = 4-aryl-2,6-bis(oxazolin-2-yl)pyridine)
Akifumi Kimura; Takayuki Ishida
AIP Conference Proceedings, American Institute of Physics Inc., 1929, 020025/1-7, 22 Jan. 2018, Peer-reviwed, Spin-crossover (SCO) is a reversible transition between low-spin (LS) and high-spin (HS) states by external stimuli like heat. The SCO behavior of [Fe(Ar-pybox)2](ClO4)2 was investigated, where Ar-pybox stands for 4-aryl-2,6-bis(oxazolin-2-yl)pyridine with Ar = 4-pyridyl (4Py), 3-thienyl (3Th), and phenyl (Ph). They were characterized by means of single-crystal X-ray diffraction study, being consistent with the results of the magnetic measurements. The SCO temperatures (T1/2) in the polycrystalline state were determined to be 360 and 230 K for Ar = 4Py and Ph, respectively. The 3Th derivative possessed a HS state in all the temperature range. The solution susceptometry was also performed to purge intermolecular interaction and rigid crystal lattice effects, affording T1/2 = 310, 240, and 240 K for Ar = 4Py, 3Th, and Ph, respectively, in acetone. The substituent effect analysis using the Hammett substituent constant (σp) clarified that electron-withdrawing groups raise T1/2. A plausible model describing the substituent effect on T1/2 is proposed based on d-π interaction. The present result is regarded as a successful example of crystal field engineering.
International conference proceedings, English - Unexpected complexes of a [3+3] cycloadduct from biphenyl-3,5-diyl bis(tert-butyl nitroxide) with gadolinium(III) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate
Hiroyasu Sekine; Takayuki Ishida
Chemistry Letters, Chemical Society of Japan, 47, 1, 74-77, 2018, Peer-reviwed, Coordination reaction of biphenyl-3,5-diyl bis(tert-butyl nitroxide) and [Gd(hfac)3(H2O)2] gave unexpected complexes containing a novel dimerized ligand via a [3+3] cycloaddition of the benzene rings, as revealed by means of crystallographic analysis. Magnetic study of the product was performed to confirm the diamagnetic nature of the ligand having four nitrone groups.
Scientific journal, English - Preparation of Superparamagnetic Fe3O4 Nanoparticles from Iron Sand Mediated by Soft Template and Their Performance as Antibacterial Agent
A. Taufiq; A.F. Muyasaroh; S. Sunaryono; H. Susanto; E. Suarsimi; N. Hidayat; N. Mufti; A. Okazawa; T. Ishida; Darminto
The Journal of Magnetics, The Korean Magnetics Society, 23, 337-344, 2018, Peer-reviwed
Scientific journal, English - Spin-Crossover Temperature Predictable from DFT Calculation for Iron(II) Complexes with 4-Substituted pybox and Related Heteroaromatic Ligands
A. Kimura; T. Ishida
ACS Omega, ACS, 3, 6737-6747, 2018, Peer-reviwed
Scientific journal, English - A Triplet Biradical with Double Bidentate Sites Based on tert-Butyl Pyridyl Nitroxides as a Candidate for Strong Ferromagnetic Couplers
A. Okazawa; Y. Terakado; T. Ishida; N. Kojima
New Journal of Chemistry (Journal Back Cover), RSC, 42, 17874-17878, 2018, Peer-reviwed
Scientific journal, English - Study on imidazolate-bridged divalent copper ion complexes capped with tris(1-pyrazolyl)methane
Tamizo Kogane; Akihiro Ondo; Masaru Yamasaki; Takuya Kanetomo; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 136, 64-69, Nov. 2017, Peer-reviwed, Four kinds of non-substituted imidazolate(im)-bridged copper(II) complexes using tris(1-pyrazolyl) methane (pz(3)CH) as a capping ligand, namely, [Cu(p mu-im)(pz(3)CH)](n)X-n (X = BF4 (1), ClO4 (2), CF3SO3 (3), (SO4)(0.5) (4)) were prepared. Their crystal structures have been determined, and despite the different space groups (orthorhombic Pna2(1) for 1-3 and monoclinic P2(1)/n for 4) and the variety of counter anions, they consist of equally-spacing polymeric chains. The Cu ion in 1-3 has a quasi-six-coordination environment, while the Cu ion in 4 has a nearly five-coordination one. The Bonner-Fisher model gave the exchange coupling parameters 2J/k(B) = -98.2(16), -106.6(10), -102.0(6), and -104.2(8) K for 1-4, respectively. The strong exchange couplings originate in the equatorial coordination of the Him atoms. We revealed that the magnitude of J values is influenced by the counter anion. The usability of the neutral pz3CH capping ligand as well as anionic pz(3)BH(-) has been shown. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English - Exchange-coupled terbium-radical complex Tb-phNO showing slow reversal of magnetization
Takuya Kanetomo; Masanori Yasui; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 136, 30-34, Nov. 2017, Peer-reviwed, A novel terbium(III)-nitroxide complex [Tb-II(hfac)(3)(phNO)(H2O)] (phNO = tert-butyl phenyl nitroxide, hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) was synthesized towards development of 4f-2p compounds with strong ferromagnetic exchange coupling. There are two crystallographically independent molecules in a unit cell. The ac magnetic susceptibility at H-dC = 2000 Oe showed double chi(m)" peaks accompanied by frequency dependence and afforded U-eff((1))/k(b) = 46.3(7) K with tau((1))(0) = 1.9(3) x 10(-9) s for the high temperature peak series and U-eff((1))/k(b) = 21(2) K with tau((1))(0) = 13(9) x 10(-8) s for the low-temperature peak series. Every molecule is proven to behave as a potential single-molecule magnet (SMM). In contrast, the corresponding dysprosium(III) analogue did not exhibit meaningful out-of-phase ac magnetic susceptibility. In the strongly exchange-coupled regime owing to the direct radical coordination bond, the whole molecular electron counting may provide a useful criterion to predict Kramers molecules as potential SMM candidates. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English - Chemical trend on the lanthanide-radical exchange coupling
Takayuki Ishida; Takeshi Nakamura; Takumi Kihara; Hiroyuki Nojiri
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 136, 149-154, Nov. 2017, Peer-reviwed, From the high-frequency electron paramagnetic resonance spectra on [Ln(hfac)(3)(TMIO)(2)] (Ln = Tb, Dy; TMIO = 1,1,3,3-tetramethylisoindolin-2-oxyl; hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) the level-crossing fields of the radical signal of the Tb and Dy complexes were determined to be 21.9(3) and 20(2) T, respectively. The observation of a single signal is consistent with the two-fold molecular symmetry. The coupling constants were evaluated, giving J(Tb-rad)/k(B) = -4.47(4) K and J(Dy-rad)/k(B) = -3.2(4) K. Since the exchange coupling constant in [Gd(hfac)3(TMIO)(2)] has already been determined to be J(Gd-rad)/k(B) = -12.5(4) K from the magnetic susceptibility measurements, the lanthanide-dependence on |JLn-rad| was concluded as |J(Gd-rad)| > |J(Tb-rad)| > |J(Dy-rad)| in this series. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English - Structural variations in (CuL)(2)Ln complexes of a series of lanthanide ions with a salen-type unsymmetrical Schiff base(H2L): Dy and Tb derivatives as potential single-molecule magnets
Prithwish Mahapatra; Soumavo Ghosh; Naoki Koizumi; Takuya Kanetomo; Takayuki Ishida; Michael G. B. Drew; Ashutosh Ghosh
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 46, 36, 12095-12105, Sep. 2017, Peer-reviwed, A new series of heterometallic trinuclear Cu(2)Ln complexes [lanthanide ions Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)] has been synthesized using a Cu(II)-metalloligand derived from a N2O2 donor unsymmetrical Schiff base, H2L (where H2L = N-alpha-methylsalicylidene-N'-salicylidene-1,3-propanediamine), and structurally characterized. Among these complexes, [ (CuL)(2)Gd(NO3)(3)(CH3CN)(2)] (1), [ (CuL)(2)Tb(NO3)(3)(CH3CN)(2)] (2) and [ (CuL)(2)Dy(NO3)(3)(CH3CN)(2)] (3) are isomorphic and isostructural. In these complexes two metalloligands coordinate to the central Ln(III) (Ln = Gd, Tb and Dy respectively) ion in a transoid fashion via mu(2)-phenoxido oxygen atoms. The Ln(III) ions are deca-coordinated with a distorted tetradecahedron geometry. The two terminal Cu(II) ions of the complexes possess a hexa-coordinated distorted octahedral geometry. In contrast, in complexes [ (CuL)(2)Ho(NO3)(3)(CH3CN)], (4) and [ (CuL)(2) Er(NO3)(3)(CH3CN)] -0.5(CH3CN) (5), the two metalloligands coordinated to the Ln(III) ions in a cisoid fashion. The Ho(III) ion in 4 is nona-coordinated with a distorted tricapped trigonal prismatic geometry and the Er(III) ion in 5 is octacoordinated with a distorted square antiprismatic geometry. The two terminal Cu(II) ions in complexes 4 and 5 are penta-coordinated with a distorted square-pyramidal geometry. The dc magnetic susceptibilities and field dependent magnetization measurement of complex 1 reveal the occurrence of ferromagnetic interactions between Cu(II) and Gd(III) ions as well as intermolecular antiferromagnetic interactions. Both complexes 2 and 3 show ferromagnetic interactions between Cu(II) and Ln(III) ions. The ac magnetic susceptibilities of all the complexes were also recorded and it was found that only complexes 2 and 3 exhibit slow relaxation of magnetization reorientation below 10 K at 2000 Oe applied dc field, this being characteristic of single molecule magnets.
Scientific journal, English - Pybox-iron(II) spin-crossover complexes with substituent effects from the 4-position of the pyridine ring (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine)
Akifumi Kimura; Takayuki Ishida
Inorganics, MDPI Multidisciplinary Digital Publishing Institute, 5, 3, 52/1-12, 01 Sep. 2017, Peer-reviwed, Invited, Spin-crossover (SCO) behavior of a series of [Fe(X-pybox)2](ClO4)2 was investigated, where X-pybox stands for 4-X-substituted 2,6-bis(oxazolin-2-yl)pyridine with X = H, Cl, Ph, CH3O, and CH3S. We confirmed that the mother compound [Fe(H-pybox)2](ClO4)2 underwent SCO above room temperature. After X was introduced, the SCO temperatures (T1/2) were modulated as 310, 230, and 330 K for X = Cl, Ph, and CH3S, respectively. The CH3O derivative possessed the high-spin state down to 2 K. Crystallographic analysis for X = H, Cl, CH3O, and CH3S was successful, being consistent with the results of the magnetic study. Distorted coordination structures stabilize the HS (high-spin) state, and the highest degree of the coordination structure distortion is found in the CH3O derivative. A plot of T1/2 against the Hammett substituent constant σp showed a positive relation. Solution susceptometry was also performed to remove intermolecular interaction and rigid crystal lattice effects, and the T1/2's were determined as 260, 270, 240, 170, and 210 K for X = H, Cl, Ph, CH3O, and CH3S, respectively, in acetone. The substituent effect on T1/2 became very distinct, and it is clarified that electron-donating groups stabilize the HS state.
Scientific journal, English - Forced proximity of nitroxide groups in pincer compounds with a xanthene spacer
Naoki Koizumi; Takayuki Ishida
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 58, 29, 2804-2808, Jul. 2017, Peer-reviwed, We designed bisnitroxide compounds where the radical sites are located close to each other in a molecule. Two new pincer-type bisnitroxide compounds have been synthesized, involving xanthene-4,5-diyl as a spacer and tert-butyl phenyl nitroxides as arms. From the X-ray crystal structure analysis, the shortest intramolecular interatomic N center dot center dot center dot N and O center dot center dot center dot O distances respectively are 5.074(6) and 5.258(6) (A) over circle for the m,m'-derivative and 3.624(3) and 3.771(3) (A) over circle for the p,p'-derivative. The N center dot center dot center dot O distance in the latter satisfies the empirical criterion for possible dimerizationidegradation reaction accompanied by dia-/paramagnetic transition. However, the magnetic study clarified paramagnetic behavior in all the temperature range. According to a singlet-triplet model, antiferromagnetic couplings were characterized with 2j/k(B) = 7.71(2) and -8.83(4) K for the m,m' and p,p'-derivatives, respectively. The present result suggests that a more flexible spacer is required for realization of possible dia-/paramagnetic transition. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English - Spin-Parity Behavior in the Exchange-Coupled Lanthanoid-Nitroxide Molecular Magnets
T. Ishida
IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing, 202, 1, 012001/1-10, 31 May 2017, Peer-reviwed, Invited, To develop lanthanoid-based magnetic materials and relevant devices, reliable prescriptions for molecular/crystal design have long been desired. Ln3+-ion dependence on the molecular magnetism was investigated in the isomorphous series [Ln(hfac)3(2pyNO)] (Ln = Tb, Dy, Ho, Er), where 2pyNO stands for tert-butyl 2-pyridyl nitroxide as a paramagnetic ligand, and hfac for 1,1,1,5,5,5-hexafluoropentane-2,4-dionate. The slow magnetization reversal was evaluated as an indication of single-molecule magnets (SMMs) by out-of-phase ac magnetic susceptibility χ". Whereas the Tb3+ (4f8) and Ho3+ (4f10) derivatives exhibited frequency-dependent χ", practically null χ" was recorded for the Dy3+(4f9) and Er3+ (4f11) derivatives. As for another series with Ln/radical = 1/2, [Ln(hfac)3(TEMPO)2] complexes were prepared (Ln = Tb, Dy, Ho, Er, Tm
TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl). The Dy3+ and Er3+ derivatives showed appreciable χ", but the Tb3+, Ho3+, and Tm3+ derivatives did not. Thus, the S = 1/2 paramagnetic ligands play a role of a spin-parity switch to regulate whether the compound behaves as an SMM. In the strongly exchange-coupled regime owing to the direct radical coordination bond, the whole molecular electron counting may provide a useful criterion to predict Kramers molecules and accordingly to explore potential SMM candidates.
International conference proceedings, English - A ground triplet dinuclear copper(II) spiro-complex involving tetraiminoneopentane
Akifumi Kimura; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 126, 45-48, Apr. 2017, Peer-reviwed, Tetralds(2-pyridylmethyleneimino)neopentane (L) was designed to form a spiro-structure after complex formation, where L plays a role of a double tetradentate bridging ligand. The X-ray diffraction study of [Cu2L(CF3SO3)(4)] clarified that the molecular structure was topologically spiro but the two coordination basal planes were not orthogonal with the dihedral angle of 49.8(1)degrees. The chi T-m value of [Cu2L(CF3SO3)(4)] showed a small increase on cooling below 10 K, indicating the presence of ferromagnetic coupling. Fitting to a singlet-triplet model gave 2J/k(B)= +0.293(7) K. The density-functional-theory Calculation of the [Cu2L](4+) core reproduced the ferromagnetic coupling. Furthermore, from another calculation after removal of the neopentyl skeleton, through-bond interaction is clarified to be major in the exchange mechanism. The intervening spa-hybridized carbon atoms may be spin-polarized. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English - Giant Exchange Coupling Evidenced with a Magnetization Jump at 52 T for a Gadolinium-Nitroxide Chelate
Takuya Kanetomo; Takumi Kihara; Atsushi Miyake; Akira Matsuo; Masashi Tokunaga; Koichi Kindo; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 56, 6, 3310-3314, Mar. 2017, Peer-reviwed, The Gd-radical complex [Gd-III(hfac)(3)(6bpyN0)] (6bpyNO = 2,2'-bipyridin-6-yl tert-butyl nitroxide; Hhfac = 1,1,1,5,5,5-hexafluoropentane2,4-dione) showed a magnetization jump at 52 T observed in a pulsed-field facility, corresponding to an exchange coupling constant of -17.4 K. Furthermore, hysteretic behavior due to a relatively slow magnetization reversal was recorded around 2 T. From the high-frequency EPR study, the exchange coupling between Gd and radical spins accompanies an anisotropic character, which is responsible for both the broad jump and the slow magnetization reversal.
Scientific journal, English - Notably Strong Antiferromagnetic Interaction in a Methylene-bridged Bis(dihydrophenanthridin-N-oxyl)
Takuya Kanetomo; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 46, 2, 188-190, Feb. 2017, Peer-reviwed, The magnetic study of bis{(5,6-dihydro-6-methylphenanthridin-5-oxyl-6-yl)}methane revealed a practically diamagnetic character, though the crystal structure analysis indicates the presence of two nitroxide groups in a molecule. Two chromophores form a "pseudo-ipso" pancake-like dimer. DFT calculation study confirmed the notably strong intramolecular antiferromagnetic coupling.
Scientific journal, English - Circular and Chainlike Copper(II)-Lanthanide(III) Complexes Generated by Assembly Reactions of Racemic and Chiral Copper(II) Cross-Linking Ligand Complexes with Ln(III)(NO3)(3)center dot 6H(2)O (Ln(II) = Gd-III, Tb-III, Dy-III)
Takahiro Ueno; Takeshi Fujinami; Naohide Matsumoto; Masaki Furusawa; Ryo Irie; Nazzareno Re; Takuya Kanetomo; Takayuki Ishida; Yukinari Sunatsuki
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 56, 3, 1679-1695, Feb. 2017, Peer-reviwed, The 1:1 assembly reaction of the racemic form of the crosslinking ligand complex Na[ (CuLdpen)-L-II(1R2R/1S2S)] with Ln(III)(NO3)36H2O gave the centrosymmetric circular (Cu(II)Ln(III))(2) complex [ (CuLdpen)-L-II(1R2R/1S2S)Ln(III)(NO3)2]2 (1Ln: Ln = Gd, Tb, Dy), while the reaction of the enantiopure form Na[ (CuLdpen(1R2R))-L-II] with Ln(III)(NO3)36H2O gave the chiral chainlike (Cu(II)Ln(III))(1)8 complex [Cu(II)L(dpen(1R2R))Ln(III)(NO3)2(CH3CN)]18CH3CN (2Ln: Ln = Gd, Tb, Dy), where {(CuLdpen(1R2R))-L-II is (N((1R,2R)2(((E)3ethoxy2oxybenzylidene)amino)1,2diphenylethyl)2oxybenzamide)copper(II) and {(CuLdpen)-L-II(1R2R/1S2S) is the racemic mixture of {(CuLdpen(1R2R))-L-II and {(CuLdpen)-L-II(1S2S). The copper(II) component functions as a crosslinking ligand complex and bridges two Ln(III) ions at two phenoxo oxygen atoms and one ethoxy oxygen atom, as well as at an amido oxygen atom. For 1Ln, two binuclear species of [Cu(II)L(dpen(1R2R))Ln(III)(NO3)(2)] and [ (CuLdpen)-L-II(1S2S)Ln(III)(NO3)(2)] with opposite chiralities are linked by two amido oxygen atoms O3 and O3* to form a centrosymmetric circular structure with GdCu = 3.370(1) A and GdCu* = 5.627(1) A. For 2Ln, binuclear species with the same chirality are bridged by GdO3* = 2.228(5) A to form a chiral chainlike structure with GdCu = 3.3348(9) A and GdCu* = 6.2326(9) A. The bridged angles through the amido group of GdO3*C7* are 133.9(5) and 177.6(4) for 1Gd and 2Gd, respectively. The magnetic susceptibilities of 1Gd and 2Gd were analyzed by the spinonly Hamiltonian on the basis of the circular tetranuclear ((CuGdIII)-Gd-II)(2) and linear chainlike ((CuGdIII)-Gd-II)(1)8 structures, respectively. The (CuGdIII)-Gd-II magnetic interactions through two phenoxo bridges and a threeatom NCO bridge, J(1) and J(2), are both ferromagnetic to be J1 = +4.6 cm(1) and J(2) = +1.8 cm(1) for 1Gd and J(1) = +4.2 cm(1) and J(2) = +0.037 cm(1) for 2Gd. The J(2) value of 2Gd is much smaller than that of 1Gd. When the temperature was lowered, 1Ln and 2Ln (Ln = Tb, Dy) showed a decrease in the Delta MT vs T plot due to crystal field effects on the Ln(III) ion (Stark splitting) and an increase due to the ferromagnetic Cu(II)Ln(III) interaction. The magnetization values of 1Ln and 2Ln (Ln = Tb, Dy) without liquid paraffin are considerably larger than the corresponding values with liquid paraffin, indicating the presence of strong magnetic anisotropy. 1Tb and 1Dy showed frequency dependence of ac magnetic susceptibility under zero external dc magnetic field, showing the behavior of singlemolecule magnets (SMMs). 2Tb and 2Dy showed no frequency dependence under a zero external magnetic field but showed a meaningful frequency dependence under an external magnetic field. Their energy barriers, Delta/k(B), estimated by the Arrhenius plots are 29.4(6) and 20.6(3) K for 1Tb and 2Tb under dc bias fields of 0 and 1000 Oe, respectively, and those of 1Dy and 2Dy are 13.1(9) K and 16.4(2) K under dc bias fields of 0 and 1000 Oe, respectively.
Scientific journal, English - Development of Biradical Ligands toward [2x2] Molecular Grids
Kana Ichihashi; Yasuhiro Mazaki; Shouhei Ohba; Takayuki Ishida
IRAGO CONFERENCE 2016: 360 DEGREE OUTLOOK ON CRITICAL SCIENTIFIC AND TECHNOLOGICAL CHALLENGES FOR A SUSTAINABLE SOCIETY, AMER INST PHYSICS, 1807, 020018/1-7, 2017, Peer-reviwed, Introduction of 2p spins into molecular grids is rare. We prepared 4,6-bis{3-(4,4,5,5-tetramethylimidazolin-1yloxyl- 3-oxido-2-yl)-1H-pyrazol-1-yl} pyrimidine (bis 'nitronyl nitroxide') and its bisdeoxygenated derivative (bis` imino nitroxide') as a building block for [2x2] molecular grids. Electron spin resonance spectra were satisfactorily simulated with the corresponding biradical models. The magnetic susceptibility measurements revealed the presence of two radical groups in a molecule. X-Ray crystal structure analysis of the bis` nitronyl nitroxide' derivative clarified the molecular structure constructed as designed. However, the geometries around the single bonds between pyrimidine and pyrazole rings were configured to be transoid (anti) in the crystal. A dichloromethane molecule was incorporated as a guest.
International conference proceedings, English - Structures and Magnetic Properties of Transition Metal Complexes Involving 2,2 '-Bipyridin-6-yl Nitroxide
Akihiro Ondo; Takayuki Ishida
IRAGO CONFERENCE 2016: 360 DEGREE OUTLOOK ON CRITICAL SCIENTIFIC AND TECHNOLOGICAL CHALLENGES FOR A SUSTAINABLE SOCIETY, AMER INST PHYSICS, 1807, 020023/1-6, 2017, Peer-reviwed, New complexes doubly chelated with two paramagnetic ligands, [M-II(6bpyNO)(2)](ClO4)(2)center dot xCH(3)OH [M = Mn (x = 0.53), Ni (x = 1); 6bpyNO = 2,2 '- bipyridin- 6- yl tert- butyl nitroxide] were prepared. The X- ray crystallographic analysis revealed the isomorphous [M(6bpyNO)(2)](2+) structure. The magnetic measurements clarified antiferromagnetic 2J(Mn-rad/kB) = - 112(2) K and ferromagnetic 2J(Ni-rad/kB) = + 384(4) K, based on a symmetrical model H = - 2JM-rad(S-M center dot S-rad1 + S-M center dot S-rad2). The coupling mechanism is explained in terms of the 3d(5) and 3d(8) spin configurations leading to the dp-pp overlap in the Mn complex and the ds-pp orthogonal arrangement in the Ni complex along the metal-radical bonds.
International conference proceedings, English - An iron(II) complex tripodally chelated with 1,1,1-tris(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour
Takayuki Ishida; Takuya Kanetomo; Masaru Yamasaki
ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY, INT UNION CRYSTALLOGRAPHY, 72, 797-+, Nov. 2016, Peer-reviwed, Invited, The spin-crossover phenomenon is a reversible low-and high-spin transition caused by external stimuli such as heat. In the novel iron(II) complex salt tetraphenylphosphonium tris(thiocyanato-kappa N)[1,1,1-tris(pyridin-2-yl) ethane-kappa N-3,N',N"]ferrate(II), (C24H20P)[Fe(NCS)(3)(C17H15N3)], the Fe-N bond lengths are in the range 2.027 (2)-2.089 (2) angstrom, indicating that the specimen consists of comparable molar fractions of the low-and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place at around 290 K.
Scientific journal, English - Spectroscopic and magnetic studies of erbium(III)-TEMPO complex as a potential single-molecule magnet: Interplay of the crystal-field and exchange coupling effects
Miroslaw Karbowiak; Czeslaw Rudowicz; Takeshi Nakamura; Rina Murakami; Takayuki Ishida
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 662, 163-168, Oct. 2016, Peer-reviwed, Crystallographic, spectroscopic, and magnetic studies of three-center systems: lanthanoid-Ln(3+) ions doubly-coordinated by TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals [Ln-TEMPO2] are reported. The temperature dependence of alternating-current magnetic susceptibility indicates the single-molecule-magnet behavior of Er-TEMPO2, exhibiting relatively slow magnetization relaxation. Well-resolved absorption spectra were obtained only for Er-TEMPO2. Other samples yielded spectra not amenable for meaningful interpretation. The crystal-field parameters (CFPs) determined from the measured Er3+-energy levels served as starting CFPs for fitting the direct-current magnetic susceptibility result. Compatibility of the so-determined and fine-tuned CFPs, and interplay between crystal-field related effects and exchange-coupling effects are considered. Exchange couplings in Ln-TEMPO2 appear antiferromagnetic and unexpectedly large. (C) 2016 Elsevier B.V. All rights reserved.
Scientific journal, English - Strongest Ferromagnetic Coupling in Designed Gadolinium(III)-Nitroxide Coordination Compounds
Takuya Kanetomo; Toru Yoshitake; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 55, 16, 8140-8146, Aug. 2016, Peer-reviwed, Three novel gadolinium(III) radical complexes [Gd-III(hfac)(3)(H2O)(L)] [Gd-L; L = tert-butyl phenyl nitroxide (phNO) and its derivatives (tert-butyl 3-tolyl nitroxide and tert-butyl 4-tert-butylphenyl nitroxide)] were synthesized, and all compounds showed ferromagnetic coupling, obeying the empirical relation: out-of-plane coordination of the Gd ion from the radical pi system favors ferromagnetic coupling. In particular, Gd-phNO has a considerably large torsion angle around Gd-O-N-C-sp(2) (69.8(9)degrees on average) and the largest ferromagnetic coupling parameter (2J/k(B) = +18.0(4) K) in Gd nitroxide compounds ever known. The validity of our molecular design was assessed on the basis of the magneto-structure relation analysis with many literature data including various paramagnetic ligating groups.
Scientific journal, English - Syntheses, Crystal Structure and Magnetic Properties of an Unprecedented One-Dimensional Coordination Polymer Derived from an {(NiL)(2)Ln} Node and a Pyrazine Spacer (H-2 L = N, N '-Bis(salicylidene)-1,3-propanediamine, Ln = Gd, Tb and Dy)
Soumavo Ghosh; Prithwish Mahapatra; Takuya Kanetomo; Michael G. B. Drew; Takayuki Ishida; Ashutosh Ghosh
CHEMISTRYSELECT, WILEY-V C H VERLAG GMBH, 1, 11, 2722-2729, Jul. 2016, Peer-reviwed, In order to investigate the coordinative interaction of the [ (NiL)-L-II] metalloligand with lanthanides (H2L = N, N'-bis(salicylidene)-1,3-propanediamine or H2salpn) and the building block potential of the resultant unstable {((NiL)-L-II)(2)Ln(III)} (Ln(III) = Lanthanides) complex with a short spacer pyrazine (pyz), three heterometallic coordination polymers of formulae [{(NiL)(2)Ln(NO3)(3)}pyz](n) center dot 1.5nH(2)O [Ln= Gd (1), Tb (2) and Dy (3)] have been synthesized. In these compounds the central Ln(III) ion is connected to two terminal [NiL] metalloligands through mu(1,1)-diphenoxido bridges to form the trinuclear node with three nitrato coligands (LnO(9) monocapped square-antiprism). The coordinative preference of pyrazine ligand towards the Ni-II-centre of the trinuclear units leads to the formation of these tailored 1D-zigzag coordination polymers with transoidtrinuclear nodes. The magnetization at 1.8 K for 1 (10.4 mu(B) at 7 T) indicates the presence of Gd - Ni ferromagnetic coupling through the phenoxido bridges. The exchange parameter was determined to be + 0.179(4) K from the magnetic susceptibility measurement. Both in-phase and outof- phase ac magnetic measurements under an applied dc magnetic field reveal temperature dependence of the susceptibility at different frequencies below 5 K for compound 3, characteristic of single molecule magnets (SMMs) or polymeric aggregates of SMMs.
Scientific journal, English - Luminescent Dy-III single ion magnets with same N6O3 donor atoms but different donor atom arrangements, 'fac'-[Dy-III(HLDL-ala)(3)]center dot 8H(2)O and 'mer'-[Dy-III(HLDL-phe)(3)]center dot 7H(2)O
Daisuke Hamada; Takeshi Fujinami; Suguru Yamauchi; Naohide Matsumoto; Naotaka Mochida; Takayuki Ishida; Yukinari Sunatsuki; Masanobu Tsuchimoto; Cecilia Coletti; Nazzareno Re
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 109, 120-128, Apr. 2016, Peer-reviwed, Two Dym complexes with same N603 donor atoms but different donor atom arrangements 'fac'-[Dy-III(HLDL-ala)(3)]center dot 8H(2)O (1) and 'mer'-[Dy-III(HLDL-phe)(3)]center dot 7H(2)O (2) were synthesized, where H2LDL-ala and H2LDL-phe are tridentate NNO ligands of N-Rimidazol-4-yl)methylidene]-DL-alanine and N-[ (imidazol-4-yl)methylidene]-DL-phenylalanine, respectively. Each Dy-III ion is coordinated by three mono-deprotonated mono-negative NNO tridentate ligands to form a nona-coordination geometry of a tricapped trigonal prism (TTP). 1 consists of enantiomers 'fac'-[Dy-III(HLD-ala)(3)], and 'fac'-[Dy-III(HLL-ala)(3)], while 2 consists of 'mer'-[Dy-III(HLD-phe)(2)(HLL-phe)] and 'mer'-[Dy-III(HLD-phe)(HLL-ala)(2)]. The temperature dependence of the magnetic susceptibilities and field-dependence of the magnetization of two complexes showed the different magnetic profiles and the Stark splitting of the ground state H-6(15/2) due to the crystal field effect on Dy-III ion (4f(9), J = 15/2, S = 5/2, L = 5, g(J) = 4/3, H-6(15/2)). Luminescence spectra were observed and the fine structures assigned to the F-4(9/2) -> H-6(15/2) transitions are partially observed. 1 and 2 showed an out-of phase signal with frequency-dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of field induced single ion magnet (SIM). The ac magnetic susceptibilities under 1000 Oe dc field of 2 showed the maximum peaks at the higher temperature than those of 1, indicating that the energy barrier of 2 is larger than that of 1. (C) 2016 Elsevier Ltd. All rights reserved.
Scientific journal, English - Ferromagnetic Chains of Ground Triplet 5-Methoxy-1,3-phenylene Bis(tert-butyl nitroxide)
Toru Yoshitake; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 45, 4, 391-393, Apr. 2016, Peer-reviwed, A new biradical, 5-methoxy-1,3-phenylene bis(tert-butyl nitroxide), was synthesized and structurally characterized. The magnetic susceptibility measurement indicates that each molecule behaved as an S = 1 species even at 300 K and that ferromagnetic chains were formed with the intermolecular coupling constant of 2J/k(B) = +2.52(5) K. The methoxy oxygen atom plays an important role in crystal engineering and magnetic coupling.
Scientific journal, English - Thermally Activated Paramagnets from Diamagnetic Polymers of Biphenyl-3,5-diyl Bis(tert-butyl Nitroxides) Carrying Methyl and Fluoro Groups at the 2 '- and 5 '-Positions
Toru Yoshitake; Hiroki Kudo; Takayuki Ishida
CRYSTALS, MDPI AG, 6, 3, 30/1-9, Mar. 2016, Peer-reviwed, Three new biradicals2',5'-dimethyl-, 2'-fluoro-5'-methyl-, and 5'-fluoro-2'-methyl- biphenyl-3,5-diyl bis(tert-butyl nitroxides)were synthesized. The magnetic susceptibility measurements revealed their diamagnetism below and around room temperature. The nitroxide groups are located close to each other in an intermolecular fashion to form a weakly covalent head-to-tail (NO)(2) ring. Biradical molecules are connected on both radical sites, constructing a diamagnetic chain. The dimethyl derivative underwent a structural phase transition at 83 degrees C, clarified via differential scanning calorimetry and powder X-ray diffraction, and a paramagnetic solid phase with S = 1 irreversibly appeared. The other analogues exhibited a similar irreversible upsurge of the magnetic susceptibility on heating, but the transition was characterized as the melting.
Scientific journal, English - Trigonal Bipyramid Ni3Cl3O2 Cluster Showing the High-Spin S=3 Ground State with Uniaxial Magnetic Anisotropy
Yumi Ida; Hiroyuki Nojiri; Takayuki Ishida
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 89, 2, 226-236, Feb. 2016, Peer-reviwed, We have prepared a novel nickel(II) trinuclear compound [Ni-3(tmen)(3)(mu(2)-Cl)(3)(mu(3)-OMe)(mu(3)-OH)](BPh4)center dot 0.5MeOH center dot 0.5CH(2)Cl(2) (1; tmen: N,N,N',N'-tetramethylethylenediamine) with a trigonal bipyramid molecular structure, where the basal plane consists of Ni-3(mu(2)-Cl)(3) atoms. Two known compounds [Ni-3(tmen)(3)X-4(OH)]X (X = Cl (2), Br (3)) were also investigated. Magnetic study clarified the ground high-spin (S = 3) state, and the intramolecular exchange coupling parameters were determined as 2J/k(B) = 18.0 +/- 0.2, 27.2 +/- 0.2, and 19.6 +/- 0.2 K for 1, 2, and 3, respectively. Crystallographic analysis clarified the unique geometry of 1. The molecular axes are aligned almost parallel in the crystallographic b axis. Relatively short intermolecular Cl center dot center dot center dot Cl distances (3.725(1) and 3.847(2) angstrom) are found among linearly arrayed complex ions. A single-crystal magnetic study gave a zero-field-splitting parameter D-S=3/k(B) = -2.2 +/- 0.1K. An intermolecular exchange coupling parameter was determined as 2j/k(B) = -0.15 +/- 0.01 K from simulation. A pulsed-field magnetization study at 0.5 K for 1 showed a jump around 1.2 T, which is explained in terms of intermolecular interaction. Alternating current magnetic susceptibility measurements revealed the Arrhenius behavior with E-a = 10.1 +/- 0.8 K at zero bias field. Therefore, the magnetic properties of 1 can be understood as an antiferromagnetic chain made of potential single-molecule magnets.
Scientific journal, English - A designed room-temperature triplet ligand from pyridine-2,6-diyl bis(tert-butyl nitroxide)
Hinako Kawakami; Asato Tonegawa; Takayuki Ishida
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 45, 4, 1306-1309, 2016, Peer-reviwed, The magnetic study on newly developed 4-mesitylpyridine-2,6-diyl bis(tert-butyl nitroxide) shows that almost the whole population has a ground triplet state at room temperature, and the ability of complex formation as a tridentate triplet ligand was proven with a diamagnetic yttrium(III) ion.
Scientific journal, English - Luminescent Single-Ion Magnets from Lanthanoid(III) Complexes with Monodentate Ketone Ligands
Takuya Kanetomo; Takayuki Ishida
IRAGO CONFERENCE 2015: 360 DEGREE OUTLOOK ON CRITICAL SCIENTIFIC AND TECHNOLOGICAL CHALLENGES FOR A SUSTAINABLE SOCIETY, AMER INST PHYSICS, 1709, 020015/1-6, 2016, Peer-reviwed, We synthesized [Ln(III)(hfac)(3)(H2O)(L)] (abbreviated as Ln-L; Ln = Gd, Tb, Eu; L = DTBK (di-t-butyl ketone), BP (benzophenone)), in which the carbonyl oxygen atom was coordinated to the Ln ion center, despite of such bulky substituents. Their crystal structures were determined by means of X-ray diffraction study. Gd-DTBK is completely isomorphous to the di-t-butyl nitroxide derivative and accordingly can be regarded as a model with the ligand spin masked. The ac magnetic susceptibility measurements on Tb-DTBK and -BP showed frequency dependence, characteristic of single-ion magnets. They also displayed photoluminescence in the solid state at room temperature. The quantum yields of the luminescence of Tb-DTBK and -BP (lambda(ex) = 360 nm) were improved to 57 and 35%, respectively, from that of the starting material [Tb-III(hfac)(3)(H2O)(2)] (28% at lambda(ex) = 370 nm). Similarly, the quantum yields for Eu-DTBK and -BP were 8 and 15%, respectively, with lambda(ex)= 400 nm, while that of the starting material [Eu-III(hfac)(3)(H2O)(2)] was 4% at lambda(ex) = 400 nm.
International conference proceedings, English - Magnetic Exchange Interaction in Gadolinium(III) Complex Having Aliphatic Nitroxide Radical TEMPO
Takeshi Nakamura; Takayuki Ishida
IRAGO CONFERENCE 2015: 360 DEGREE OUTLOOK ON CRITICAL SCIENTIFIC AND TECHNOLOGICAL CHALLENGES FOR A SUSTAINABLE SOCIETY, AMER INST PHYSICS, 1709, 020016/1-3, 2016, Peer-reviwed, We synthesized a new compound, [Gd(hfac)(3)(MeOH)(TEMPO)] (TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) with the metal/radical ratio of 1/1. This compound has an advantage in the magnetic analysis, because the exchange coupling system is described with a unique coupling parameter J, when compared to the structure and magnetic properties of the previous TEMPO and related complexes. The X-ray crystal structure analysis of [Gd(hfac)(3)(MeOH)(TEMPO)] revealed the N-O and Gd-O(N) bond lengths are 1.299(9) and 2.307(5) angstrom, respectively, and the Gd-O-N angle is 149.4(5)degrees. The magnetic study clarified the Gd3+-radical antiferromagnetic interaction of 2J/k(B) = -3.5(1) K.
International conference proceedings, English - Pyridine-2,6-diyl Dinitroxides as Room-Temperature Triplet Ligands
Hinako Kawakami; Asato Tonegawa; Takayuki Ishida
IRAGO CONFERENCE 2015: 360 DEGREE OUTLOOK ON CRITICAL SCIENTIFIC AND TECHNOLOGICAL CHALLENGES FOR A SUSTAINABLE SOCIETY, AMER INST PHYSICS, 1709, 020017/1-6, 2016, Peer-reviwed, We have proposed tert-butyl 2-pyridyl nitroxide radicals as a promising paramagnetic chelating ligand, where the direct radical-metal bond leads to strong magnetic interaction. We successfully synthesized and isolated PyBN derivatives (pyridine-2,6-diyl bis(tert-butyl nitroxides)). The molecular and crystal structures of the target biradicals, MesPyBN, AntPyBN and tBuOPyBN were determined from the X-ray crystal structure analysis, which possess mesityl, 9-anthryl and tert-butoxy groups at the 5-position of the pyridine ring, respectively. The ground triplet state was characterized by means of SQUID susceptometry for each compound. On heating, the chi T-m values of all the PyBN derivatives increased and reached a plateau at ca. 1.0 cm(3) K mol(-1) at 300 K. It implies that biradicals behaved as triplet molecules even at room temperature, or 2J/k(B) >> 300 K. From the decay monitored in solution electron-spin resonance spectroscopy, MesPyBN was the most persistent, while tBuOPyBN was the most reactive, of the three.
International conference proceedings, English - Strong Ferromagnetic Exchange Interactions in Hinge-like Dy(O2Cu)(2) Complexes Involving Double Oxygen Bridges
Yumi Ida; Soumavo Ghosh; Ashutosh Ghosh; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 54, 19, 9543-9555, Oct. 2015, Peer-reviwed, Two trinuclear isomeric compounds, [{(Cu-II(salpn))(Me(CO)Me)}(2)Dy-III(NO3)(3)] (1) and [{Cu-II(salpn)}(2)Dy-III(H2O)(NO3)(3)]center dot MeOH (2), along with one polymeric compound, {[{Cu-II(salpn)}(2)Dy-III(NO3)(3)bpy]center dot MeOH center dot H2O}(n) (3), were synthesized using a metalloligand, [Cu-II(salpn)], where H(2)salpn and bpy stand for N,N'-bis(salicylidene)-1,3-propanediamine and 4,4'-bipyridine, respectively. Compounds 1 and 2 were selectively prepared with two solvents: the less polar acetone led to the exclusive crystallization of 1 with a transoid trinudear architecture, while more polar solvent methanol provided sole construction of 2 with a cisoid trinuclear architecture. Compound 3 was prepared from 1 or 2 after bpy was introduced as a bridge. The Dy and Cu ions are doubly bridged with oxygen atoms, and the core DyO2Cu skeletons are characterized by different "butterfly angles" of 140.9(1)degrees, 147.1(19)degrees, and 142.4(2)degrees for 1, 2, and 3, respectively. We have examined the molecular structures and magnetic properties of 1-3 using high-frequency electron paramagnetic resonance (HF-EPR), magnetization, and magnetic susceptibility techniques. These compounds showed slow magnetization reversal in the measurements of alternating current magnetic susceptibility. We analyzed EPR frequency-field diagrams using an effective spin-Hamiltonian including only one doublet of Dy sublevels and found that the exchange couplings are ferromagnetic in all compounds. The exchange coupling parameters J(Dy-Cu) of 1, 2, and 3 were determined as 2.25 +/- 0.05, 1.82 +/- 0.04, and 1.79 +/- 0.04 K, respectively. These values are larger than those found in previous research using EPR analysis on [Cu-II(L-A)(C3H6O)Dy-III(NO3)(3)] (H2LA = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane) and [ (DyL2B)-L-III(NO3)(2){Cu-II(CH3OH)}(2)](NO3)(CH3OH) (H2LB = 2,6-bis(acetylaceto)pyridine). The present result shows an advantage of doubly oxygen-bridged motifs to built strong ferromagnetic interactions between lanthanide and transition metal ions. We found that the exchange coupling strength is sensitive to the structural parameters such as bond angles, bond lengths, and butterfly angles. Precise determination of the exchange parameters would contribute to development of exchange-coupled 4f-3d heterometallic complexes.
Scientific journal, English - First Iron(II) Spin-crossover Complex with an N5S Coordination Sphere
Masaru Yamasaki; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 44, 7, 920-921, Jul. 2015, Peer-reviwed, A novel dinuclear iron(II) complex [{Fe(py(3)COH)(NCS)(mu-NCS)}(2)](PrOH)(2) was prepared. Each Fe ion is coordinated with three N atoms from tridentate tris(2-pyridyl)methanol (py(3)COH) and two N and one S atoms from NCS- coligand. It showed a one-step gradual spin-crossover at T-1/2 = 207K. This compound is the first spin-crossover material having an FeN5S coordination structure.
Scientific journal, English - Relationship between Torsion and Anisotropic Exchange Coupling in a Tb-III-Radical-Based Single-Molecule Magnet
Michael L. Baker; Takuya Tanaka; Rina Murakami; Seiko Ohira-Kawamura; Kenji Nakajima; Takayuki Ishida; Hiroyuki Nojiri
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 54, 12, 5732-5738, Jun. 2015, Peer-reviwed, The incorporation of paramagnetic ligands within rare-earth ion clusters exhibiting large magnetic anisotropy has provided significant advancement in the design of single-molecule magnets (SMMs) with large blocking temperatures. However, the exchange interaction in such systems is complex and difficult to probe by conventional magnetometry techniques, and little is known about the structural relationships. Inelastic neutron scattering and terahertz electron paramagnetic resonance measurements are used complimentarily to investigate the large exchange interaction between a rare earth-radical pair in a Tb-III-based SMM complex. The origin of the exchange interaction is investigated for two molecular species in the crystallographic unit cell that exhibit different bonding structures between Tb-III and a 2pyNO radical. A correlation between the Tb-O-N-C torsion angles and the magnitudes of exchange couplings is found. Interestingly, a large nondegeneracy within the ground-state doublet is present for the larger torsion angle species. It is essential to consider the balance of two channels of exchange coupling, 2p-4f hybridization and 2p-5d charge transfer, to explain this characteristic behavior. The former channel gives the antiferromagnetic interaction, and the latter gives the ferromagnetic one. When an effective (J) over cap = 1/2 Ising-type Hamiltonian is applied, the exchange couplings are evaluated to be antiferromagnetic J(z) = 9.89 meV (79.8 cm(-1)) for the low torsion angle (3.8 degrees) species and J(z) = 7.39 meV (59.6 cm(-1)) for the larger torsion angle (15.8 degrees) species. It is also found that a small percentage of the transverse exchange component must be included for the larger torsion angle to account for the observed nondegenerate ground state. The symmetry of the exchange couplings is discussed by considering the characters of d and f orbitals.
Scientific journal, English - Structures and magnetic properties of three compounds from imidazolate-bridged copper(II) pyrazolylborate complexes
Tamizo Kogane; Takuya Kanetomo; Hiroki Muroyama; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 89, 149-154, Mar. 2015, Peer-reviwed, Three kinds of imidazolate-bridged copper(II) complexes using pz(3)BH anion as a capping ligand, namely, [Cu-4(mu-im)(4)(pz(3)BH)(4)][Cu(pz(3)BH)(2)](2) (I), polymorphic [Cu-4(mu-im)(4)(pz(3)BH)(4)] (1t), and [Cu(mu-im)(pz(3)BH)](n), (1p) were afforded (Him = imidazole; pz(3)BH = hydrotris(1-pyrazolyl)borate). Their crystal structures were determined to reveal that 1 and it involve a tetranuclear macrocycle while 1p consists of a polymeric chain. The im nitrogen atoms occupied the copper equatorial positions. The magnetic susceptibility measurements showed that the im bridges played the role of an antiferromagnetic coupler. The Bonner-Fisher model with the Heisenberg spin Hamiltonian as H = -Sigma 2JS(i)center dot Si+1 gave 2J/k(B) = -115.5(6)K for 1p. The magnitude of the present interaction belongs to the largest class, when compared with those of the known im-bridged copper(II) complexes. (C) 2015 Elsevier Ltd. All rights reserved.
Scientific journal, English - Strong exchange couplings in lanthanide complexes with an aliphatic nitroxide radical 1,1,3,3-tetramethylisoindolin-2-oxyl
Takeshi Nakamura; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 87, 302-306, Feb. 2015, Peer-reviwed, We prepared crystalline [REIII(hfac)(3)(TMIO)(2)] (RE = Gd, Y; abbreviated as RE-TMIO2), where TMIO and hfac stand for 1,1,3,3-tetramethylisoindolin-2-oxyl and 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, respectively. Two compounds are isomorphous in a C2/c space group. The paramagnetic TMIO ligand serves as an O-donor, and there are two TMIO moieties related with twofold symmetry in each molecule. The discrete molecular system guarantees the three- or two-centered exchange-coupling model. Magnetic study clarified that Gd-TMIO2 behaved as a ground S-total = 5/2 species with the intramolecular exchange couplings 2J(Gd-TMIO)/k(B) = -12.5(4) K and 2J(TMIO-TMIO)/kB = -27(2) K from an isosceles triangle model. Superexchange interaction across the diamagnetic Y ion was characterized in Y-TMIO2 with 2J(TMIO-TMIO)/k(B) = -21.3(2) K from the singlettriplet model. DFT calculation on Y-TMIO2 and a series of model compounds involving Rb+, Sr2+, Y3+, and Zr4+ suggests a possible mechanism involving ligand-to-metal charge transfer interaction for the relatively strong radicalradical couplings. (C) 2014 Elsevier Ltd. All rights reserved.
Scientific journal, English - Spin-crossover thermal hysteresis and light-induced effect on iron(II) complexes with tripodal tris(2-pyridyl)methanol
Masaru Yamasaki; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 85, 795-799, Jan. 2015, Peer-reviwed, The X-ray crystal structure of Me4N[Fe(py(3)COH)(NCS)(3)](1-PrOH)(0.5)(H2O)(2) [1; py(3)COH stands for tris(2-pyridyl)methanol] was successfully determined, clarifying that the complex has a pseudo-trigonal molecular arrangement, though the space group was P (1) over bar. Possible pi-pi interaction is operative between the pyridine rings from neighboring [Fe(py(3)COH)(NCS)(3)](-) ions. After annealing of 1 at 400 K, the resultant compound was characterized to be Me4N[Fe(py(3)COH)(NCS)(3)](H2O) (1'), which showed a relatively abrupt spin-crossover (SCO) with thermal hysteresis. Combining the differential thermal analysis results, the SCO temperatures were determined as T-1/2 down arrow= 224 K and T-1/2 up arrow = 246 K. Compound 1' also showed light-induced excited spin-state trapping (LIESST), as indicated with the chi T-m increased to a 32% level of the high-spin moment upon Xe-lamp irradiation at 5 K. The LIESST effect disappeared at around 26 K on heating. The complex ion [Fe(py(3)COH)(NCS)(3)](-) is a rare anionic SCO and LIESST building block. (C) 2014 Elsevier Ltd. All rights reserved.
Scientific journal, English - Synthesis of mixed-valence hexanuclear Mn(II/III) clusters from its Mn(II) precursor: variations of catecholase-like activity and magnetic coupling
Paramita Kar; Yumi Ida; Takuya Kanetomo; Michael G. B. Drew; Takayuki Ishida; Ashutosh Ghosh
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 44, 21, 9795-9804, 2015, Peer-reviwed, One Mn(II) coordination polymer, [Mn(o-(NO2)C6H4COO)(2)(pyz)(H2O)](n) (1), has been synthesized and oxidized with n-Bu4NMnO4 in non-aqueous media to two mixed-valence hexanuclear Mn(II/III) complexes [ (Mn2Mn4O2)-Mn-III-O-II(pyz)(0.61)/(MeOH)(0.39)(o-(NO2)C6H4COO)(10)center dot(H2O)center dot{(CH3)(2)CO}(2)]center dot(CH3)(2)CO (2) and [ (Mn2Mn4O2)-Mn-III-O-II- pyz)(0.28)/(MeCN)(3.72)(o-(NO2)C6H4COO)(10)center dot(H2O)] (3) (where pyz = pyrazine). All three complexes were characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, and variable-temperature magnetic measurements. The structural analyses reveal that complex 1 is comprised of linear chains of pyz bridged Mn(II), which are further linked to one another by syn-anti carboxylate bridges, giving rise to a two-dimensional (2D) net. Complexes 2 and 3 feature mixed valence [ (Mn2Mn4II)-Mn-III] units in which each of the six manganese centres reside in an octahedral environment. Apart from the variations in terminal ligands (acetone for 2 and acetonitrile for 3), the complexes are very similar. Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, the catecholase-like activity of the complexes has been studied and it is found that the mixed valent Mn-6 complexes (2 and 3) are much more active towards aerial oxidation of catechol compared to the Mn(II) complex (1). Variable-temperature (1.8-300 K) magnetic susceptibility measurements showed the presence of antiferromagnetic coupling in all three complexes. The magnetic data have been fitted with a 2D quadratic model derived by Lines, giving the exchange constant J/k(B) = -0.0788(5) K for 1. For 2 and 3, antiferromagnetic interactions within the Mn6 cluster have been fitted with models containing three exchange constants: J(A)/k(B) = -70 K, J(B)/k(B) = -0.5 K, J(C)/k(B) = -2.9 K for 2 and J(A)/k(B) = -60 K, J(B)/k(B) = -0.3 K, J(C)/k(B) = -2.8 K for 3.
Scientific journal, English - Intermediate-paramagnetic phases with a half and a quarter spin entities in fluorinated biphenyl-3,5-diyl bis(tert-butyl nitroxides)
Takuya Konno; Hiroki Kudo; Takayuki Ishida
JOURNAL OF MATERIALS CHEMISTRY C, ROYAL SOC CHEMISTRY, 3, 30, 7813-7818, 2015, Peer-reviwed, A new ground-triplet biradical, 2',5'-difluorobiphenyl-3,5-diyl bis(tert-butyl nitroxide), showed spin-transition-like behaviour at T-C up arrow = 182 K and T-C down arrow = 181 K. This compound had a quarter of the nominal amount of paramagnetic spins in the low-temperature phase and a half in the high-temperature phase. Another new 3'-monofluoro derivative maintained a half amount of the spins as a single solid phase, which is isomorphous to the high-temperature phase of the difluoro analogue. During the spin transition, a reversible bond formation-cleavage between nitrogen and oxygen atoms takes place at neighbouring nitroxide groups in an intermolecular fashion. These intermediate states emerge during multi-step spin transition from the unsymmetrical biradicals as designed.
Scientific journal, English - Heating-rate dependence of spin-crossover hysteresis observed in an iron(II) complex having tris(2-pyridyl)methanol
Masaru Yamasaki; Takayuki Ishida
JOURNAL OF MATERIALS CHEMISTRY C, ROYAL SOC CHEMISTRY, 3, 30, 7784-7787, 2015, Peer-reviwed, Me4N[Fe(py(3)COH)(NCS)(3)](H2O) showed an abrupt spin-crossover with thermal hysteresis, and temperature-scan rate dependence was recorded upon heating at 10-0.02 K min(-1). At the slowest scan the product of magnetic susceptibility and temperature initially increased at 246 K, then decreased at around 250 K and finally increased again to reach the high-spin state at around 280 K. A polymorphic spin-crossover model is plausible.
Scientific journal, English - Single-molecule magnet involving strong exchange coupling in terbium(III) complex with 2,2 '-bipyridin-6-yl tert-butyl nitroxide
Takuya Kanetomo; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY FRONTIERS, CHINESE CHEMICAL SOC, 2, 9, 860-866, 2015, Peer-reviwed, A novel terbium(III)-radical complex [Tb-III(hfac)(3)(6bpyNO)] (Tb-6bpyNO; 6bpyNO = 2,2'-bipyridin-6-yl tert-butyl nitroxide) was synthesized. The intramolecular antiferromagnetic interaction in Tb-6bpyNO was confirmed by comparison with the magnetic properties of [Tb-III(hfac)(3)(6bpyCO)] (Tb-6bpyCO; 6bpyCO = 2,2'-bipyridin-6-yl tert-butyl ketone) together with [Y-III(hfac)(3)(6bpyNO)]. Tb-6bpyNO showed a hysteresis loop with negligible coersivity below 1.6 K. The dispersion of the magnetic susceptibility with an applied bias field of 2000 Oe gave the energy barrier E-a/k(B) = 21.1(8) K. In contrast, Tb-6bpyCO did not behave as a single-molecule magnet, despite having practically the same crystal field.
Scientific journal, English - Spin-Crossover Hysteresis of [Fe^II(LHiPr)2(NCS)2] (LHiPr = N-2-Pyridylmethylene-4-isopropylaniline) Accompanied by Isopropyl Conformation Isomerism
N. Mochida; A. Kimura; T. Ishida
Magnetochemistry, MDPI, 1, 17-27, 2015, Peer-reviwed, Invited
Scientific journal, English - Metal-organic frameworks from two-dimensional copper(II) complexes bridged with N-methylpyrazine-2-carboxamide
Mizuki Yoshida; Takuya Kanetomo; Hiroki Muroyama; Takayuki Ishida; Tamizo Kogane
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 81, 493-498, Oct. 2014, Peer-reviwed, Two kinds of mpyza-bridged copper(II) complexes, [Cu(mpyza)(2)](BF4)(2)center dot 2H(2)O (1) and [Cu(mpyza)(2)] (PF6)(2)center dot 1.5H(2)O (2) were prepared (mpyza = N-methylpyrazine-2-carboxamide). Their crystal structures have been determined, and despite the different space groups (Pc and P2(1)/c for I and 2, respectively) they exhibit a similar metal-organic framework. Four Cu ions construct rectangular arrangement providing an infinite molecular two-dimensional grid, which have an equatorial-axial-type coordinated pyrazine bridge. Compounds 1 and 2 contain two or one and a half uncoordinated water molecules in a void space. The former liberates the water at 45 degrees C, but the latter does not below 170 degrees C, being consistent with the channel of 1 loosely packed with the counter anion. The magnetic studies revealed that they involved very weak Cu---Cu superexchange antiferromagnetic interactions with J/k(B) = -0.277(5) and -0.166(5) K for 1 and 2, respectively, analyzed on the basis of a two-dimensional model. (C) 2014 Elsevier Ltd. All rights reserved.
Scientific journal, English - Crystal Field Splitting of the Ground State of Terbium(III) and Dysprosium(III) Complexes with a Triimidazolyl Tripod Ligand and an Acetate Determined by Magnetic Analysis and Luminescence
Seira Shintoyo; Keishiro Murakami; Takeshi Fujinami; Naohide Matsumoto; Naotaka Mochida; Takayuki Ishida; Yukinari Sunatsuki; Masayuki Watanabe; Masanobu Tsuchimoto; Jerzy Mrozinski; Cecilia Coletti; Nazzareno Re
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 53, 19, 10359-10369, Oct. 2014, Peer-reviwed, Terbium(III) and dysprosium(III) complexes with a tripodal N-7 ligand containing three imidazoles (H3L) and a bidentate acetate ion (OAc-), [Ln(III)(H3L)(OAc)](ClO4)(2)center dot MeOH center dot H2O (Ln = Tb, 1; Ln = Dy, 2), were synthesized and studied, where H3L = tris[2-(((imidazol-4-yl)methylidene)amino)ethyl]amine. The Tb-III and Dy-III complexes have an isomorphous structure, and each Tb-III or Dy-III ion is coordinated by the tripodal N-7 and the bidentate acetate ligands, resulting in a nonacoordinated capped-square-antiprismatic geometry. The magnetic data, including temperature dependence of the magnetic susceptibilities and field dependence of the magnetization, were analyzed by a spin Hamiltonian, including the crystal field effect on the Tb-III ion (4f(8), J = 6, S = 3, L = 3, g(J) = 3/2, F-7(6)) and the Dy-III ion (4f(9),J = 15/2, S = 5/2, L = 5, g(J) = 4/3, H-6(15/2)). The Stark splittings of the ground states F-7(6) of the Tb-III ion and H-6(15/2) of the Dy-III ion were evaluated from the magnetic analyses, and the energy diagram patterns indicated an easy axis (Ising type) anisotropy for both complexes, which is more pronounced for 2. The solid-state emission spectra of both complexes displayed sharp bands corresponding to the f-f transitions, and the fine structures assignable to the D-5(4) -> F-7(6) transition for 1 and the F-6(9/2) -> H-6(15/2) transition for 2 were related to the energy diagram patterns from the magnetic analyses. 1 and 2 showed an out-of-phase signal with frequency dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of a field-induced SIM.
Scientific journal, English - Strongest Exchange Coupling in Gadolinium(III) and Nitroxide Coordination Compounds
Takuya Kanetomo; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 53, 20, 10794-10796, Oct. 2014, Peer-reviwed, The largest antiferromagnetic coupling parameter was characterized to be 2J/k(B) = -15.9(2) K in [Gd(hfac)(3)(6bpyNO)], where 6bpyNO stands for 2,2'-bipyridin-6-yl tert-butyl nitroxide. This molecule was designed according to the empirical relation: more planar chelate favors stronger antiferromagnetic coupling. The Gd-Orad bond is relatively short owing to the tridentate character.
Scientific journal, English - Synthesis, Structure, Luminescence, and Magnetic Properties of a Single-Ion Magnet "mer"-[Tris(N-[ (imidazol-4-yl)-methylidene]-DL-phenylalaninato)terbium(III) and Related "fac"-DL-Alaninato Derivative
Suguru Yamauchi; Takeshi Fujinami; Naohide Matsumoto; Naotaka Mochida; Takayuki Ishida; Yukinari Sunatsuki; Masayuki Watanabe; Masanobu Tsuchimoto; Cecilia Coletti; Nazzareno Re
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 53, 12, 5961-5971, Jun. 2014, Peer-reviwed, Two Tb-III complexes with the same N6O3 donor atoms but different coordination geometries, "fac"- [Tb-III(HLDL-ala)(3)]center dot 7H(2)O (1) and "mer"- [Tb-III(HLDL-phe)(3 center dot)7H(2)O (2), were synthesized, where H2LDL-ala and H2L2DL-phe are N-imidazol-4-yl)methylidene-DL-alanine and -DL-phenylalanine, respectively. Each Tb-III ion is coordinated by three electronically mononegative NNO tridentate ligands to form a coordination geometry of a tricapped trigonal prism. Compound 1 consists of enantiomers "fac"-[Tb-III(HLD-ala)(3)] and "fac"-[Tb-III(HLL-ala)(3)], while 2 consists of "mer"-[Tb-III(HLD-phe)(2)(HLD-Phe)(HLL-Phe)(2)]. Magnetic data were analyzed by a spin Hamiltonian including the crystal field effect on the Tb-III ion (4f(8), J = 6, S = 3, L = 3, gi = 3/2, F-7(6)). The Stark splitting of the ground state 7F6 was evaluated from magnetic analysis, and the energy diagram pattern indicated easyplane and easy-axis (Ising type) magnetic anisotropies for 1 and 2, respectively. Highly efficient luminescences with phi = 0.50 and 0.61 for 1 and 2, respectively, were observed, and the luminescence fine structure due to the D-5(4) -> F-7(6) transition is in good accordance with the energy diagram determined from magnetic analysis. The energy diagram of 1 shows an approximate single-well potential curve, whereas that of 2 shows a double- or quadruple-well potential within the F-7(6) multiplets. Complex 2 displayed an onset of the out-of-phase signal in alternating current (ac) susceptibility at a direct current bias field of 1000 Oe on cooling down to 1.9 K. A slight frequency dependence was recorded around 2 K. On the other hand, 1 did not show any meaningful out-of-phase ac susceptibility. Pulsed-field magnetizations of 1 and 2 were measured below 1.6 K, and only 2 exhibited magnetic hysteresis. This finding agrees well with the energy diagram pattern from crystal field calculation on 1 and 2. DFT calculation allowed us to estimate the negative charge distribution around the Tb-III ion, giving a rationale to the different magnetic anisotropies of 1 and 2.
Scientific journal, English - Linker Stoichiometry-Controlled Stepwise Supramolecular Growth of a Flexible Cu2Tb Single Molecule Magnet from Monomer to Dimer to One-Dimensional Chain
Soumavo Ghosh; Yumi Ida; Takayuki Ishida; Ashutosh Ghosh
CRYSTAL GROWTH & DESIGN, AMER CHEMICAL SOC, 14, 5, 2588-2598, May 2014, Peer-reviwed, A trinuclear complex [ (CuL)(2)Tb(H2O)(NO3)(3)]center dot MeOH center dot H2O(1) is synthesized by using a metalloligand [CuL] (H2L = N,N'-bis(salicylidene)-1,3-propanediamine or salpn). This complex is used as a new 3d-4f metallatecton for stepwise supramolecular oligomerization along with a simple diimine linker, 4,4'-bipyridine (bpy). A ratio of metallatecton/linker = 2:1 is conducive for the formation of a dimer [{(CuL)(2)Tb(H2O)(NO3)(3)}(2)bpy]center dot 2MeOH center dot 4H(2)O (2), whereas a higher proportion of linker at a ratio of 1:1 gives rise to a zigzag one-dimensional coordination polymer {[ (CuL)(2)Tb(NO3)(3)bpy]center dot MeOH center dot 2H(2)O}(infinity) (3). The inherent conformational flexibility of the trinuclear (CuL)(2)Tb node which is folded (cisoid) for 1 and 2 (asymmetric TbO9 tricapped trigonal prism) and unfolded (transoid) for 3 (a C-2-symmetric TbO10 tetradecahedron) seems to stabilize the crystal packing of these coordination-driven self-assemblies. The rapidly saturated magnetization at 1.8 K for 1 (11 mu B) and 2 (22 mu(B)) clearly indicates the presence of Tb-Cu ferromagnetic coupling through the phenoxido bridges of the Cu(mu(1,1)-O)(2)Tb(mu(1,1)-O)(2)Cu cores. A slow saturation behavior has been found for 3 (9.5 mu(B)). Both in-phase and out-of-phase ac Magnetic measurements of 1 under an applied dc magnetic field reveal temperature dependence of the susceptibility at different frequencies below 5 K, characteristic of single molecule magnets (SMMs), which is conserved in 2 and 3 signifying oligo- and polymeric aggregates of SMMs.
Scientific journal, English - Multifunctional pi-Expanded Macrocyclic Oligothiophene 6-Mers and Related Macrocyclic Oligomers
Masahiko Iyoda; Keita Tanaka; Hideyuki Shimizu; Masashi Hasegawa; Tohru Nishinaga; Tomohiko Nishiuchi; Yoshihito Kunugi; Takayuki Ishida; Hiroyuki Otani; Hiroyasu Sato; Koji Inukai; Kazukuni Tahara; Yoshito Tobe
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 136, 6, 2389-2396, Feb. 2014, Peer-reviwed, Multifunctional pi-expanded macrocyclic oligothiophene 6-mer 1, as well as 9- (2) and 12-mers (3), was synthesized using a McMurry coupling reaction as the key step. The 6-mer 1 was converted to cyclo[6](2,5-thienylene-ethynylene) (4) by using a bromination-dehydrobromination procedure. From X-ray analysis, the crystal structures of nonplanar 1 and round-shaped 2 and 4 were elucidated. STM showed that 4 formed a self-assembled monolayer at the liquid/solid interface to produce a hexagonal porous network. Chemical oxidation of 1, 2, and 4 with 1 and 2 equiv of Fe(ClO4)(3) produced 1(center dot+) and 1(2+), 2(center dot+) and 2(2+), and 4(center dot+) and 4(2+), respectively. Although oligothiophene radical cations containing beta,beta-disubstituted thiophenes usually do not form pi-dimers, 4(center dot+) clearly formed a pi-dimer owing to its planar, round shape. As for the dications of 1, 2, and 4, 12+, which has 34 pi-electrons, exhibited a large diatropic ring current effect, whereas 34 pi dication 4(2+) only showed a medium diatropic ring current effect. In contrast to 1(2+) and 4(2+), 52 pi dication 2(2+) had biradical cationic character instead of Huckel-type cyclic conjugation. Interestingly, 6-mer 1 showed polymorphism and unusual melting point behavior due to the number of stable conformations in the solid state. Single crystals of 1 melted at 176 degrees C, whereas an amorphous film of 1 crystallized in the temperature range of 80-83 degrees C to form a lamellarly stacked microcrystalline film, which melted at 139 degrees C. The polymorphism of 1 was applied to either fluorescence switching or switching of field effect transistor (FET) activity and electrical conductivity.
Scientific journal, English - Preparation and characterization of [Gd(hfac)(3)(DTBN)(H2O)] (DTBN = di-t-butyl nitroxide). Ferromagnetic Gd3+-Gd3+ super-superexchange
Takuya Kanetomo; Takayuki Ishida
CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 50, 19, 2529-2531, 2014, Peer-reviwed, The intramolecular radical-Gd antiferromagnetic coupling (2J(1)/k(B) = -11.6 K) is notably strong, as expected from our molecular design, and the intermolecular exchange coupling along the Gd-O-H...O-Gd bridges is unexpectedly ferromagnetic with the largest Gd...Gd coupling ever known (2J(2)/k(B) = + 0.12 K).
Scientific journal, English - Doubly TEMPO-coordinated gadolinium(III), lanthanum(III), and yttrium(III) complexes. Strong superexchange coupling across rare earth ions
Rina Murakami; Takeshi Nakamura; Takayuki Ishida
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 43, 15, 5893-5898, 2014, Peer-reviwed, We prepared crystalline [REIII(hfac)(3)(TEMPO)(2)] (RE = Gd, La, Y), where TEMPO and hfac stand for 2,2,6,6-tetramethylpiperidin-1-oxyl and 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, respectively. The X-ray crystal structure of TEMPO-coordinated RE compounds was determined for the first time. The Gd and Y analogues are isomorphous, and the La derivative has a similar molecular skeleton. The Gd-O(TEMPO) bond lengths were 2.322(3) and 2.354(3) angstrom with the O-Gd-O angle of 140.36(11)degrees. The magnetic study clarified that [Gd(hfac)(3)(TEMPO)(2)] behaved as a ground S-total = 7/2 species. The La and Y analogues showed the superexchange interactions across the diamagnetic ions with 2J(TEMPO1-TEMPO2)/k(B) = -14.9(1) and -49.8(2) K, respectively. Assuming the presence of a similar interaction like the Y derivative, the Gd-TEMPO exchange couplings are estimated with 2J(Gd-TEMPO)/k(B) = -12.9(5) and + 8.0(6) K.
Scientific journal, English - Polymeric one- and two-dimensional copper(I) iodide complexes showing photoluminescence tunable by azaaromatic ligands
Nobuo Kitada; Takayuki Ishida
CRYSTENGCOMM, ROYAL SOC CHEMISTRY, 16, 34, 8035-8040, 2014, Peer-reviwed, Four low-dimensional [ (Cul)(x)L](n) complexes [L = 4,6-dimethylpyrimidine (46dmpm; x = 2), 2,5-dimethylpyrazine (x = 2), 2,6-dimethylpyrazine (x = 1), 3,5-dimethylpyridine (x = 1)] were structurally characterized. All the compounds exhibited a (Cul)(n) polymeric motif and the azaaromatic ligands were coordinated to each copper(I) ion, thus giving infinite two-dimensional networks for the x = 2 compounds and one-dimensional chain structures for the x = 1 compounds. The photoluminescent properties were investigated in the solid state at ambient temperature, and blue, green, and orange emissions were observed for the pyridine, pyrimidine, and pyrazine compounds, respectively. The energy level of the pi* orbital of the azaaromatic compounds regulates the emission color, in agreement with the halide-to-ligand charge-transfer mechanism. A photoluminescence quantum yield of 73% was recorded for [ (Cul)(2)(46dmpm)](n).
Scientific journal, English - Crystal structures and magnetic properties of two-dimensional copper(II) complexes bridged with pyrazine-2-carboxamide
Mizuki Yoshida; Takashi Shimada; Takayuki Ishida; Tamizo Kogane
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 66, 75-80, Dec. 2013, Peer-reviwed, A variety of [Cu(pyza)(2)](X)(2) (X = BF4 (1), ClO3 (2), ClO4 (3), PF6 (4), AsF6 (5)) were synthesized (pyza = pyrazine-2-carboxamide). The crystal structures of 1-5 have been determined to be isomorphous to that of known 3 in a monoclinic P2(1)/c space group. They form a quadratic copper(II) array with pyza bridges. The 1- and 4-nitrogen atoms in the pyrazine ring are coordinated to copper ions at equatorial and axial positions, respectively. Complexes 1-5 showed very weak antiferromagnetic interactions with J/k(B) = -0.439(6), -0.321(5), -0.304(1), -0.209(3), and -0.264(5) K, respectively, analyzed on the basis of an antiferromagnetic two-dimensional model. The magnitude of J almost correlates with the Cu center dot center dot center dot Cu distance and the cell volume. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English - Magnetic study on radical-gadolinium(III) complexes. Relationship between the exchange coupling and coordination structure
Takayuki Ishida; Rina Murakami; Takuya Kanetomo; Hiroyuki Nojiri
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 66, 183-187, Dec. 2013, Peer-reviwed, Antiferro- and ferromagnetic couplings were observed in [Gd(hfac)(3)(2pyNO)(H2O)] and [Gd(hfac)(3)(-HNN)(2)], respectively, where 2pyNO stands for tert-butyl 2-pyridyl nitroxide and HNN for 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide. The magnitude of the former is the largest in Gd-nitroxide complexes (2J/k(B) = -13.8(3) K). An empirical relation between the exchange coupling and torsion angle Gd-O-N-C is drawn, where large torsion (>36 degrees) favors ferromagnetic coupling. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English - Exchange Coupling and Its Chemical Trend Studied by High-Frequency EPR on Heterometallic [Ln(2)Ni] Complexes
Atsushi Okazawa; Takashi Shimada; Norimichi Kojima; Shunsuke Yoshi; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 52, 23, 13351-13355, Dec. 2013, Peer-reviwed, We applied high-frequency electron paramagnetic resonance to trinuclear 4f-3d heterometallic complexes, [{Ln(hfac)(3)}(2){Ni(dpk)(2)(py)(2)}] (Ln = Y, Gd, Tb, and Ho; hfac = hexafluoroacetylacetonate, dpk = di-2-pyridyl ketoximate, and py = pyridine), and determined the exchange parameter J(Ln-Ni) as well as nickel(II) zero-field splitting parameters. In contrast to the antiferromagnetic Dy analogue, ferromagnetic couplings were precisely characterized as J(Gd-Ni)/k(B) = +0.301(4) K, J(Tb-Ni)/k(B) = +0.216(12) K, and J(Ho-Ni)/k(B) = +0.110(3) K (defined as -J(Ln-Ni)Sigma J(Ln)(z)S(Ni)).
Scientific journal, English - Determination of Crystal-Field Energy Levels and Temperature Dependence of Magnetic Susceptibility for Dy3+ in [Dy2Pd] Heterometallic Complex
Miroslaw Karbowiak; Czeslaw Rudowicz; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 52, 22, 13199-13206, Nov. 2013, Peer-reviwed, This study is the first in a series of experimental and theoretical investigations of the crystal-field (CF) energy levels obtained from optical electronic spectra for selected heterometallic 4f-3d compounds intensively studied for the development of novel single-molecule magnets (SMMs). An intriguing question is why the [{Dy-III(hfac)(3)}(2)Cu-II(dpk)(2)] (abbreviated as [Dy2Cu]; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, Hdpk = di-2-pyridyl ketoxime) has antiferromagnetic coupling, whereas [Gd2Cu] and heavy [Ln(2)Cu] systems usually show ferromagnetic coupling. As the first step to explain this peculiarity, the recently synthesized complex, [Dy2Pd], is investigated. This complex is isostructural with [Dy2Cu] yet contains the diamagnetic Pd ion instead of the magnetic Cu(II) ion. Experimental energy levels of Dy3+ ions in the powder [Dy2Pd] sample were determined from the 4.2 K absorption spectra. CF analysis was performed yielding the fitted free ion and CF parameters. The number of freely varied parameters was restricted using the superposition model. The fittings yield very satisfactory agreement between the experimental and the calculated energy levels (rms = 12.0 cm(-1)). The energies and exact composition of the state vector for the ground multiplet H-6(15/2) of Dy3+ are determined. These results are used for the simulation of the temperature dependence of the magnetic susceptibility, which enables the theoretical interpretation of the experimentally measured magnetic susceptibility in the range 1.8-300 K for the [Dy2Pd] complex. This study provides background for the subsequent investigation of the magnetic exchange interactions in the pertinent heterometallic complexes.
Scientific journal, English - Synthesis, Structure, Luminescent, and Magnetic Properties of Carbonato-Bridged Zn(2)(II)Ln(2)(II) Complexes [ (mu(4)-CO3)(2){Zn(II)L(n)Ln(II)(NO3)}(2)) (Ln(III) = Gd-III, Tb-III, Dy-III; L-1 = N,N'-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L-2 = N,N'-Bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato)
Kiyomi Ehama; Yusuke Ohmichi; Soichiro Sakamoto; Takeshi Fujinami; Naohide Matsumoto; Naotaka Mochida; Takayuki Ishida; Yukinari Sunatsuki; Masanobu Tsuchimoto; Nazzareno Re
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 52, 21, 12828-12841, Nov. 2013, Peer-reviwed, Carbonato-bridged Zn(2)(II)Ln(2)(III) complexes [ (mu(4)-CO3)(2){Zn(II)L(n)Ln(III)(NO3)}(2)]center dot solvent were synthesized through atmospheric CO2 fixation reaction of [ (ZnLn)-L-II(H2O)(2)]center dot xH(2)O, Ln(III)(NO3)(3)center dot 6H(2)O, and triethylamine, where Ln(III) = Gd-III, Tb-III, Dy-III; L-1 = N,N'-bis(3-methorry-2-oxybenzylidene)-1,3-propanediaminato, L-2 = N,N'-bis(3-ethorry-2-oxybenzylidene)1,3-propanediaminato. Each Zn(2)(II)Ln(2)(III) structure possessing an inversion center can be described as two di-mu-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO32- ions. The Zn-II ion has square pyramidal coordination geometry with N2O2 donor atoms of L-n and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L-n, two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(2)(II)Ln(2)(III) complexes are analyzed on the basis of the dicarbonato-bridged binuclear structure, as the Zn-II ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L-1) and ZnGd2 (L-2) show a ferromagnetic Gd-III-Gd-III interaction with J(Gd-Gd)Zn(2)(II)Ln(2)(III) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)(S) over cap (Gd1).(S) over cap (Gd2). The magnetic data of the complexes (Ln(III) = D 11) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of (Zn2Tb2III)-Tb-II complexes were observed, while those of (Zn2Dy2III)-Dy-II were not detected. The fine structure assignable to the D-5(4) -> F-7(6) transition of ZnTb1 and ZnTb2 is in good accord with the energy pattern from the magnetic analysis. The Zn(2)(II)Ln(2)(III) complexes (Ln(III) = Tb-III, Dy-III) showed an out-of-phase signal with frequency-dependence in alternating current susceptibility, indicative of single molecule magnet. Under a dc bias field of 1000 Oe, the signals become significantly more intense and the energy barrier, Delta/k(B), for the magnetic relaxation was estimated from the Arrhenius plot to be 39(1) and 42(8) K for ZnTb1 and ZnTb2, and 52(2) and 67(2) K for ZnDyl and ZnDy2, respectively.
Scientific journal, English - A supramolecular switch between ground high- and low-spin states using 2,2′:6′,2″-terpyridine-6,6″-diyl bis(tert-butyl nitroxide)
Takuya Konno; Kazuya Koide; Takayuki Ishida
Chemical Communications, RSC, 49, 45, 5156-5158, 07 Jun. 2013, Peer-reviwed, Biradical 2,2′:6′,2″-terpyridine-6,6″-diyl bis(tert-butyl nitroxide) (tpybNO) showed intramolecular ferromagnetic coupling with 2J/kB = +2.14(10) K and its complex [Zn(tpybNO)(MeOH) 2](BF4)2 exhibited intramolecular antiferromagnetic coupling with 2J/kB = -7.5(4) K, suggesting exchange coupling switchable by means of supramolecular chemistry. © 2013 The Royal Society of Chemistry.
Scientific journal, English - Ground triplet pyrimidine-4,6-diyl bis(tert-butyl nitroxide) as a paramagnetic building block for metal-organic frameworks
Yuta Homma; Atsushi Okazawa; Takayuki Ishida
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 54, 24, 3120-3123, Jun. 2013, Peer-reviwed, We synthesized pyrimidine-4,6-diyl bis(tert-butyl nitroxide) (pmbNO), and characterized as a biradical by means of ESR spectroscopy. The zero-field splitting parameters were vertical bar D vertical bar/hc = 2.52 x 10(-2) cm(-1) and vertical bar E vertical bar/hc = 2.34 x 10(-3) cm(-1) in frozen toluene at 100 K. Magnetic study clarified the presence of intramolecular ferromagnetic coupling with 2J/k(B) = +18.5(5) K in frozen toluene-ethanol. DFT calculation supports the ground triplet state of pmbNO. The reaction of pmbNO with Cu(hfac)(2) gave [Cu-3(pmbNO)(2)(hfac)(4)], and the structure was determined by X-ray crystallographic analysis. Though the ligand was reduced to be an anion radical, pmbNO is confirmed to work as a rigid bridge, and the nitroxide oxygen atoms can ligate the metal ions. (C) 2013 Elsevier Ltd. All rights reserved.
Scientific journal, English - Carbonato-Bridged NO(2)(II)Ln(2)(III) (Ln(III) = Gd-III, Tb-III, Dy-III) Complexes Generated by Atmospheric CO2 Fixation and Their Single-Molecule-Magnet Behavior: [ (mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(MeOH or H2O)Ln(III)(NO3)}(2)]center dot solvent [3-MeOsaltn = N,N '-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato]
Soichiro Sakamoto; Takeshi Fujinami; Koshiro Nishi; Naohide Matsumoto; Naotaka Mochida; Takayuki Ishida; Yukinari Sunatsuki; Nazzareno Re
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 52, 12, 7218-7229, Jun. 2013, Peer-reviwed, Atmospheric CO2 fixation of [Ni-II(3-MeOsaltn)(H2O)(2)]center dot 2.5H(2)O [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene) -1,3-propanediaminato], Ln(III)(NO3)(3)center dot 6H(2)O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni-2(II),Ln(2)(III) complexes [ (mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(MeOH)-Ln(III)(NO3)}(2)] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [ (mu(4)-CO3)(2){Ni-II(3-MeOsaltn)(H2O)-Ln(III)(NO3)}(2)]center dot 2CH(3)CN center dot 2H(2)O (2Gd, 2Tb, and 2Dy). For both series, each Ni(2)(II)Ln(2)(III) structure can be described as two di-mu-phenoxo-bridged Ni(II)Ln(III) binuclear units bridged by two carbonato CO32- units to form a carbonato-bridged (mu(4)-CO3)(2){Ni(2)(II)Ln(2)(III)) structure. The high-spin Ni-II ion has octahedral coordination geometry, and the Ln(III) ion is coordinated by O-9 donor atoms from Ni-II(3-MeOsaltn), bidentate NO3-, and one and two oxygen atoms of two CO32- ions. The NO3- ion for the first series roughly lie on Ln-O(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln-O(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni-II and Ln(III) ions (Ln(III) = Gd-III, Tb-III, Dy-III) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln(III)-Ln(III) magnetic interaction and/or different magnetic anisotropies of the Tb-III or Dy-III ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the (Ni2Gd2III)-Gd-II complexes but exhibited an out-of-phase signal for (Ni2Tb2III)-Tb-II and (Ni2Dy2III)-Dy-II, indicative of slow relaxation of magnetization. The energy barriers, Delta/k(B), for the spin flipping were estimated from the Arrhenius plot to be 12.2(7) and 6.1(3) K for 1Tb and 2Tb, respectively, and 18.1(6) and 14.5(4) K for 1Dy and 2Dy, respectively, under a dc bias field of 1000 Oe. Compound 1Dy showed relatively slow relaxation of magnetization reorientation even at zero dc applied field with Delta/k(B) = 6.6(4) K.
Scientific journal, English - Syntheses, structures, and magnetic properties of acetato- and diphenolato-bridged 3d-4f binuclear complexes [M(3-MeOsaltn)(MeOH) x(ac)Ln(hfac)2](M = ZnII, CuII,NiII,CoII;Ln = LaIII,GdIII, TbIII, DyIII; 3-MeOsaltn = N,N-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato; Ac = Acetato; Hfac = Hexafluoroacetylacetonato; X = 0 or 1)
Masaaki Towatari; Koshiro Nishi; Takeshi Fujinami; Naohide Matsumoto; Yukinari Sunatsuki; Masaaki Kojima; Naotaka Mochida; Takayuki Ishida; Nazzareno Re; Jerzy Mrozinski
Inorganic Chemistry, ACS, 52, 10, 6160-6178, 20 May 2013, Peer-reviwed, A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH) x(ac)Ln(hfac)2] (x = 0 for M = CuII, Zn II
x = 1 for M = CoII, NiII
Ln = Gd III, TbIII, DyIII, LaIII), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N′-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged MII- LnIII binuclear structure. The CuII-LnIII and ZnII-LnIII complexes are crystallized in an isomorphous triclinic space group P1̄, where the CuII or ZnII ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The CoII-Ln III and NiII-LnIII complexes are crystallized in an isomorphous monoclinic space group P21/c, where the Co II or NiII ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each LnIII ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of "ligand-complex" M(3-MeOsaltn), four oxygen atoms of two hfac-, and one oxygen atom of the bridging acetato ion
thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the LnIII (TbIII, DyIII) and to a lesser extent the MII (NiII, CoII) components, the magnetic interaction between MII and LnIII ions were investigated by an empirical approach based on a comparison of the magnetic properties of the MII-LnIII, ZnII-LnIII, and M II-LaIII complexes. The differences of χMT and M(H) values for the MII-LnIII, ZnII-Ln III and those for the MII-LaIII complexes, that is, Δ(T) = (χMT)MLn - (χMT) ZnLn - (χMT)MLa = JMLn(T) and Δ(H) = MMLn(H) - MZnLn(H) - MMLa(H) = JMLn(H), give the information of 3d-4f magnetic interaction. The magnetic interactions are ferromagnetic if MII = (CuII, NiII, and CoII) and Ln = (GdIII, Tb III, and DyIII). The magnitudes of the ferromagnetic interaction, JMLn(T) and JMLn(H), are in the order Cu II-GdIII >
CuII-DyIII >
CuII-TbIII, while those are in the order of M II-GdIII ≈ MII-TbIII >
M II-DyIII for MII = NiII and Co II. Alternating current (ac) susceptibility measurements demonstrated that the NiII-TbIII and CoII-TbIII complexes showed out-of-phase signal with frequency-dependence and the Ni II-DyIII and CoII-DyIII complexes showed small frequency-dependence. The energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the Ni II-TbIII and CoII-TbIII complexes, respectively, under a dc bias field of 1000 Oe. © 2013 American Chemical Society.
Scientific journal, English - A New Family of Trinuclear Nickel(II) Complexes as Single-Molecule Magnets
Rituparna Biswas; Yumi Ida; Michael L. Baker; Saptarshi Biswas; Paramita Kar; Hiroyuki Nojiri; Takayuki Ishida; Ashutosh Ghosh
CHEMISTRY-A EUROPEAN JOURNAL, WILEY-V C H VERLAG GMBH, 19, 12, 3943-3953, Mar. 2013, Peer-reviwed, Three new trinuclear nickel (II) complexes with the general composition [Ni3L3(OH)(X)](ClO4) have been prepared in which X=Cl (1), OCN (2), or N3 (3) and HL is the tridentate N,N,O donor Schiff base ligand 2-[ (3-dimethylaminopropylimino)methyl]phenol. Single-crystal structural analyses revealed that all three complexes have a similar Ni3 core motif with three different types of bridging, namely phenoxido (2 and 3), hydroxido (3), and 2-Cl (1), 1,1-NCO (2), or 1,1-N3 (3). The nickel(II) ions adopt a compressed octahedron geometry. Single-crystal magnetization measurements on complex 1 revealed that the pseudo-three-fold axis of Ni3 corresponds to a magnetic easy axis, being consistent with the magnetic anisotropy expected from the coordination structure of each nickel ion. Temperature-dependent magnetic measurements indicated ferromagnetic coupling leading to an S=3 ground state with 2J/k=17, 17, and 28K for 1, 2, and 3, respectively, with the nickel atoms in an approximate equilateral triangle. The high-frequency EPR spectra in combination with spin Hamiltonian simulations that include zero-field splitting parameters DNi/k=5, 4, and 4K for 1, 2, and 3, respectively, reproduced the EPR spectra well after a anisotropic exchange term was introduced. Anisotropic exchange was identified as Di,j/k=0.9, 0.8, and 0.8K for 1, 2, and 3, respectively, whereas no evidence of single-ion rhombic anisotropy was observed spectroscopically. Slow relaxation of the magnetization at low temperatures is evident from the frequency-dependence of the out-of-phase ac susceptibilities. Pulsed-field magnetization recorded at 0.5K shows clear steps in the hysteresis loop at 0.51T, which has been assigned to quantum tunneling, and is characteristic of single-molecule magnets.
Scientific journal, English - Formation of two drastically different MOFs based on Mn(II)-benzoate and pyrazine with a change in seasonal temperature: structural analysis and magnetic study
Paramita Kar; Yumi Ida; Takayuki Ishida; Ashutosh Ghosh
CRYSTENGCOMM, ROYAL SOC CHEMISTRY, 15, 2, 400-410, 2013, Peer-reviwed, Two new stoichiometrically and structurally very different Mn(II) coordination compounds {[Mn(pyz)(C6H5COO)(2)](C2H5OH)}(n) (1) and [Mn-5(pyz)(C6H5COO)(10)(H2O)(2)](n) (2) (where pyz = pyrazine) have been synthesized by the reaction of Mn(C6H5COO)(2)center dot 4H(2)O and pyz in 1 : 1 molar ratio in different seasons of the year. The structural analyses reveal that complex 1, which is synthesized in summer when the temperature remains around 28-40 degrees C, features a 1D molecular ladder formed by joining of syn-syn benzoate-bridged dimeric Mn(II) units by pyz. Complex 2, which is obtained in winter (temperature around 10-20 degrees C), is an unprecedented 2D rectangular sheet motif based on a 1D column constructed from syn-syn benzoate bridged repetitive Mn-5 units which are further interconnected by the pyz spacer. The compounds are interconvertible in solution: when an ethanol solution of 1 is allowed to evaporate slowly in winter or in a refrigerator (5-6 degrees C) it transformed into 2 whereas crystallization of 2 from ethanol medium in summer (28-40 degrees C) yields 1. Variable-temperature (1.8-300 K) magnetic susceptibility measurements showed presence of weak antiferromagnetic coupling in 1 that has been fitted with the van Vleck equation. The interaction in benzoate-bridged Mn-2 unit was characterized to be J = -0.586(1) cm(-1), where the spin-Hamiltonian is defined as H = -2JS(1)S(2). The interaction in 2 was also characterized with the modified van Vleck equation to be weakly antiferromagnetic.
Scientific journal, English - Single-molecule magnet [Tb(hfac)(3)(2pyNO)] (2pyNO=t-butyl 2-pyridyl nitroxide) with a relatively high barrier of magnetization reversal
Rina Murakami; Takayuki Ishida; Shunsuke Yoshii; Hiroyuki Nojiri
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 42, 38, 13968-13973, 2013, Peer-reviwed, The crystallographic analysis of the title compound shows that there are two crystallographically independent molecules in a unit cell. The magnetic study clarified that every molecule behaved as a single-molecule magnet. Two series of the out-of-phase ac susceptibility signals appeared around 10 K even at zero dc field. The activation energies (Delta) for the magnetization reversal were estimated as Delta((1))/k(B) = 39.2(3) K with tau((1))(0) = 4.2(4) x 10(-8) s and Delta((2))/k(B) = 36(2) K with tau((2))(0) = 4.1(12) x 10(-7) s, where tau(0) stands for the pre-exponential factor in the Arrhenius analysis. Magnetic hysteresis was recorded at 1.6 K by means of a pulsed-field technique. The role of exchange coupling is discussed.
Scientific journal, English - Polyether-bridged bis(tert-butyl nitroxide) paramagnetic hosts showing receptor ability to calcium(II) and barium(II) ions
Sayaka Osada; Naoki Hirosawa; Takayuki Ishida
TETRAHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 68, 31, 6193-6197, Aug. 2012, Peer-reviwed, The title compounds, Ph2bNO and Ph3bNO, were designed as a biradical paramagnetic host, and their chelation ability was confirmed by inclusion of a size-matched alkaline-earth metal ion. The crystal structures of [Ca(hfac)(2)(Ph2bNO)] and [Ba(hfac)(2)(Ph3bNO)] were determined, where Hhfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dione. The solution electron paramagnetic resonance spectra showed switching behavior. Five lines were found for Ph3bNO and charecterized as the hyperfine splitting due to the two nitrogen atoms. After addition of barium(II) ion, the spectrum turned to be three lines. Removal of the barium ion recovered the five line pattern. The present system can be regarded as a reversible magnetic-coupling switch by means of a supramolecular technique. (C) 2012 Elsevier Ltd. All rights reserved.
Scientific journal, English - Spin Crossover and Light-induced Excited Spin-state Trapping Observed for an Iron(II) Complex Chelated with Tripodal Tetrakis(2-pyridyl)methane
Naoki Hirosawa; Yuya Oso; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 41, 7, 716-718, Jul. 2012, Peer-reviwed, A novel iron(II) complex [Fe(py(4)C)(2)][Fe(py(4)C)(NCS)(3)](2) was synthesized, where py(4)C stands for tetrakis(2-pyridyl)methane. Spin crossover occurred at 161 K (T-1/2). Light-induced excited spin-state trapping was observed when irradiated with 532 nm at 10 K, and the conversion was 89%. The relaxation took place at 58 K on heating.
Scientific journal, English - Oximato-bridged light-lanthanide Ln(4)Cu complexes showing ferromagnetic Ln-Cu exchange coupling
Kei Fujiwara; Atsushi Okazawa; Norimichi Kojima; Go Tanaka; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 530, 49-54, Mar. 2012, Peer-reviwed, Heterometallic pentanuclear coordination compounds [Ln(4)(3+)Cu(2+)] involving light lanthanide ions, Ce, Pr, Nd, Sm, and Eu, were synthesized and structurally characterized. The exchange interactions between the Ln and Cu ions were evaluated by high-frequency electron paramagnetic resonance and magnetization studies, clarifying the presence of ferromagnetic exchange couplings in Nd-Cu (J(Nd-Cu)/k(B) = +0.30(6) K) and Sm-Cu (J(Sm-Cu)/k(B) = +2.08(3) K), very small couplings in Ce-Cu and Pr-Cu, and the absence in Eu-Cu. A significant chemical trend is found in the order of the atomic number. (C) 2012 Elsevier B. V. All rights reserved.
Scientific journal, English - Triply Radical-coordinated Gadolinium(III) Complex as a High-spin S=5 Assembly
Naoya Ikegaya; Takuya Kanetomo; Rina Murakami; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 41, 1, 82-83, Jan. 2012, Peer-reviwed, A discrete Gd3+ and radical complex was prepared and characterized to be [Gd(hfac)(3)(HNN)(3)] by means of X-ray crystallographic analysis, where Hhfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dione and HNN for 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide. A magnetic study revealed the presence of ferromagnetic exchange coupling with 2J/k(B) = 3.86(6) K, ascribable to the Gd-HNN interaction.
Scientific journal, English - Exchange coupling in TbCu and DyCu single-molecule magnets and related lanthanide and vanadium analogs
Takayuki Ishida; Ryo Watanabe; Kei Fujiwara; Atsushi Okazawa; Norimichi Kojima; Go Tanaka; Shunsuke Yoshii; Hiroyuki Nojiri
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 41, 44, 13609-13619, 2012, Peer-reviwed, Heterometallic coordination compounds [Cu-II(L)(C3H6O)Ln(III)(NO3)(3)] and [ (VO)-O-IV(L)(C3H6O)Ln(III)(NO3)(3)] (abbreviated as LnCu and LnV, respectively; H2L = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane; Ln = Gd, Tb, Dy, Ho, and Er) were synthesized, and the X-ray crystallographic analysis shows that their structures are isomorphous for each series. The single-molecule magnet behavior was observed for TbCu and DyCu, and the activation energies of magnetization reversal were 42.3(4) and 11.5(10) K, respectively. The magnetic exchange couplings in LnCu and LnV were precisely evaluated by means of combined high-frequency EPR and pulsed-field magnetization studies, to give J(Tb-Cu)/k(B) >= 3.3 K, J(Dy-Cu)/k(B) = 1.63(1) K, J(Ho-Cu)/k(B) = 1.09(2) K, and J(Er-Cu)/k(B) = 0.24(1) K. A monotonic decrease of ferromagnetic J(Ln-Cu) was found in the order of the atomic number, Gd-64 to Er-68. The corresponding exchange parameters in LnV are smaller than those of the Cu derivatives, and J(Gd-V) was antiferromagnetic (-3.0 K determined from the magnetization jump). A possible mechanism for the exchange coupling and chemical trend is discussed.
Scientific journal, English - A Unique Example of Structural Diversity Tuned by Apparently Innocent o-, m-, and p-Nitro Substituents of Benzoate in Their Complexes of Mn(II) with 4,4 '-Bipyridine: 1D Ladder, 2D Sheet, and 3D Framework
Paramita Kar; Rituparna Biswas; Yumi Ida; Takayuki Ishida; Ashutosh Ghosh
CRYSTAL GROWTH & DESIGN, AMER CHEMICAL SOC, 11, 12, 5305-5315, Dec. 2011, Peer-reviwed, Four new Mn(II) coordination polymers [Mn(4,4'-bpy)(C6H5COO)(2)](n) (1), [Mn(4,4'-bpy)(o-(NO2)C6H4COO)(2)](n) (2), [Mn(4,4'-bpy)(m-(NO2)C6H4COO)(2)](n) (3), and [Mn(4,4'-bpy)(p-(NO2)C6H4COO)(2)](n) (4) (where 4,4'-bpy = 4,4'-bipyridine) have been synthesized by self-assembly of the primary ligands, benzoate and the o-, m-, and p-isomers of nitrobenzoates, respectively, together with 4,4'-bpy as the secondary spacer. All four complexes were characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, and variable-temperature magnetic measurements. The structural analyses reveal that complexes 1 and 3 are constructed by linear fused chains through double syn-syn (for 1) or syn-anti (for 3) carboxylate-bridged Mn(II), which are further linked to one another by trans coordinated 4,4'-bpy bridges, giving rise to a rectangular grid-like two-dimensional (2D) net. Complex 2 features one-dimensional (ID) molecular ladder formed by both syn-syn and syn-anti carboxylate-bridged dimeric Mn (II) units which are joined alternately by 4,4'-bpy. Complex 4 is formed by fused zigzag chains of double syn-syn carboxylate-bridged Mn (II) that are connected by cis oriented 4,4'-bpy to generate an unprecedented three-dimensional (3D) framework. The dimensionality of the complexes thus varies from ID to 2D to 3D on changing the position of the nitro group from o- to m- to p- in the benzoate, showing explicitly the tuning ability of this apparently innocent substituent on the topology of the coordination polymer. Variable-temperature (1.8-300 K) magnetic susceptibility measurements showed the presence of antiferromagnetic coupling in all four complexes that have been fitted with an infinite classical-spin chain model derived by Fisher for 1, 3, and 4 (J = -0.779(2), -0.855(2), and -0.536(2) cm(-1), and van Vleck equation for 2 (J = -0.354(2) cm(-1)).
Scientific journal, English - Ferromagnetic oxovanadium(IV) complexes chelated with tetrahalosalen ligands
Kei Fujiwara; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 30, 18, 3073-3078, Nov. 2011, Peer-reviwed, Five oxoyanadium(IV) complexes [VO(X(4)salen)] have been prepared and characterized, where each benzene ring was substituted with two halogen atoms in salen (H(2)salen = N,N'-disalicylideneethylenediamine). The X-ray diffraction study on 3,3',5,5'-tetrachloro-, 3,3',5,5'-tetrabromo-, and 4,4',6,6'-tetrachlorosalen derivatives clarified their polymeric structure with the (-V=O-)(n) repeating unit. The interatomic V-V distances are 3.710(3), 3.695(3), and 3.749(3) angstrom, respectively, being shorter than that of known [VO(salpn)] (3.83 A; H(2)salpn = N,N'-disalicylidenepropylenediamine). The exchange coupling parameters (1) were determined by fitting the magnetic susceptibility data to the one-dimensional ferromagnetic model, giving 2J/k(B) = 8.2-16 K, which are the largest in the [VO(salen)] and [VO(salpn)I family. (C) 2011 Elsevier Ltd. All rights reserved.
Scientific journal, English - 2,2 '-Bipyridine-6,6 '-diyl bisnitroxide as a paramagnetic host: Encapsulation of a zinc(II) ion
Kazuya Koide; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 30, 18, 3034-3037, Nov. 2011, Peer-reviwed, A chelate complex of zinc(II) and 2,2'-bipyridine-6,6'-diyl bis(tert-butyl nitroxide) (bpybNO) with a metal/ligand ratio of 1/2 was structurally characterized to be [Zn(bpybNO)(2)][Zn(hfac)(3)](2), where Hhfac stands for 1,1,1,55,5-hexafluoropentane-2,4-dione. The magnetic susceptibility measurement indicates the presence of considerable antiferromagnetic interaction among the four S = 1/2 spins. The exchange parameter J was estimated as 2J/k(B) = -103(1) K, on the basis of a tetrahedral coupling model. The antiferromagnetic coupling is stronger after complexation than before. The density-functional theory calculation on related model compounds supports the present analysis and clarified the role of the zinc ion as a superexchange coupler. (C) 2011 Elsevier Ltd. All rights reserved.
Scientific journal, English - Single-molecule magnet behavior enhanced by magnetic coupling between 4f and 3d spins
Atsushi Okazawa; Hiroyuki Nojiri; Takayuki Ishida; Norimichi Kojima
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 30, 18, 3140-3144, Nov. 2011, Peer-reviwed, We synthesized and characterized a new compound [{Dy(hfac)(3)}(2)Pd(dpk)(2)] ([Dy(2)Pd]; Hdpk = di-2-pyridyl ketoxime), which is isostructural with the known [Dy(2)Cu] and [Dy(2)Ni]. The study of the [Dy(2)Pd] compound containing diamagnetic Pd ion is indispensable to clarify a contribution of the exchange coupling for a 4f-3d single-molecule magnet behavior. From the ac susceptibility measurements on [Dy(2)Pd], we obtained Delta/k(B) = 28.6(11) K and T(B) = 1.1 K. In accordance with the blocking behavior, the pulsed-field magnetization showed the hysteresis behavior below 1.1 K. These parameters on [Dy(2)Pd] having S(Pd) = 0 was compared with those of the derivatives having S(Cu) = 1/2 (Delta/k(B) = 47 K and T(B) = 1.8 K) and S(Ni) = 1 (Delta/k(B) = 62(4) K and T(B) = 2.5 K). The T(B) and Delta steadily increase with the increasing 3d(4d) spin quantum number. (C) 2011 Elsevier Ltd. All rights reserved.
Scientific journal, English - Exchange couplings in one-dimensionally arrayed 4f-3d heterometallic [Ln(2)Cu(2)](n) compounds: A chemical trend of the coupling parameter
Atsushi Okazawa; Kei Fujiwara; Ryo Watanabe; Norimichi Kojima; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 30, 18, 3121-3126, Nov. 2011, Peer-reviwed, Heterometallic polymeric coordination compounds [ (Ln(hfac)(2)(CH3OH)}(2){Cu(dmg)(Hdmg)}(2)](n) (abbreviated as [Ln(2)Cu(2)](n)) involving light lanthanoid ions, Pr, Nd, Sm, and Eu, were synthesized, where H(2)dmg and Hhfac stand for dimethylglyoxime and 1,1,1,5,5,5-hexafluoropentane-2,4-dione, respectively. The X-ray crystallographic analysis shows that their structures are isomorphous to those of the known heavy lanthanoid analogs. The exchange couplings were evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving ferromagnetic exchange parameters: J(Pr-cu)/k(B) = 0.039(1) K, J(Nd-cu)/k(B) = 0.38(1) K, J(sm-cu)/k(B) = 0.95(2) K, and no interaction between Eu and Cu ions. A significant trend is found in the order of the periodic table. The ferro- and antiferromagnetic 4f-3d couplings were characterized for the light and heavy lanthanoid derivatives, respectively. The magnitude of J(Ln-Cu) decreases with a decrease of the 4f-spin portion. i.e., the number of unpaired electrons, whether the coupling is ferro- or antiferromagnetic. (C) 2011 Elsevier Ltd. All rights reserved.
Scientific journal, English - Attempted synthesis of axial-equatorial pyrazine-bridged copper(II) complexes toward homometallic ferromagnetic compounds
Ryo Watanabe; Takashi Shimada; Nobumasa Koyama; Takayuki Ishida; Tamizo Kogane
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 30, 18, 3165-3170, Nov. 2011, Peer-reviwed, The introduction of a relatively bulky alkyl group at 2-position of pyrazine afforded unique mu-pyz complexes, namely, dinuclear [{Cu(hfac)(2))(2)(mu-2-isobutylpyrazine)], trinuclear [{Cu(hfac)(2)}(3)(mu-2-isopropyl-pyrazine)(2)], and polymeric [Cu(hfac)2(mu-ibupyz)](n) (Hhfac stands for 1,1,1,5,5,5-hexalluoropentane-2, 4-dione). These compounds have an axial-equatorial dinuclear moiety, which is expected to show ferromagnetic interaction. However, they exhibited practically negligible or very weak antiferromagnetic interaction. This may be due to violation of orthogonality because of the steric hindrance of the isobutyl or isopropyl groups. We analyzed the relationship between the structural deformation parameter defined as the N(eq)center dot center dot center dot N(ax)-Cu angle and the exchange coupling parameter. A critical angle, at which the sign of the magnetic coupling changes from positive to negative, is estimated to be 165(2)degrees. The present results are reasonably explained in this relation. (C) 2011 Elsevier Ltd. All rights reserved.
Scientific journal, English - Ferromagnetic Exchange Couplings Showing a Chemical Trend in Cu-Ln-Cu Complexes (Ln = Gd, Tb, Dy, Ho, Er)
Takashi Shimada; Atsushi Okazawa; Norimichi Kojima; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 50, 21, 10555-10557, Nov. 2011, Peer-reviwed, Exchange couplings in isomorphous [LnCu(2)] were evaluated by high-frequency electron paramagnetic resonance and magnetization studies. The exchange parameter J(Ln-Cu) was decreased with an increase in the atomic, number; J(Ln-Cu)/k(B) = 4.45(11), 2.27(6), 0.902(10), 0.334(3), and 0.136(8) K for Ln = Gd, Tb, Dy, Ho, and Er, respectively.
Scientific journal, English - Spin-Canted Antiferromagnetic Phase Transitions in Alternating Phenoxo- and Carboxylato-Bridged Mn-III-Salen Complexes
Paramita Kar; Pampa M. Guha; Michael G. B. Drew; Takayuki Ishida; Ashutosh Ghosh
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, WILEY-V C H VERLAG GMBH, 2011, 13, 2075-2085, May 2011, Peer-reviwed, Three new MnIII complexes, {[Mn-2(salen)(2)(OCn)](ClO4)}(n) (1), {[Mn-2(salen)(2)(OPh)](ClO4)}(n) (2) and {[Mn-2(salen)(2)(OBz)](ClO4)}(2) (3) (where salen = N,N'-bis(salicylidene)-1,2-diaminoethane dianion, OCn = cinnamate, OPh = phenylacetate and OBz = benzoate), have been synthesized and characterized structurally and magnetically. The crystal structures reveal that all three structures contain syn-anti carboxylatebridged dimeric [Mn-2(salen)(2)(OOCR)](+) cations (OOCR = bridging carboxylate) that are joined together by weak Mn center dot center dot center dot O(phenoxo) interactions to form infinite alternating chain structures in 1 and 2, but the relatively long Mn center dot center dot center dot O(phenoxo) distance [3.621(2)angstrom] in 3 restricts this structure to tetranuclear units. Magnetic studies showed that 1 and 2 exhibited magnetic long-range order at T-N = 4.0 and 4.6 K (T-N = Neel transition temperature), respectively, to give spin-canted antiferromagnetic structures. Antiferromagnetic coupling was also observed in 3 but no peaks were recorded in the field-cooled magnetization (FCM) or zero-field-cooled magnetization (ZFCM) data, indicating that 3 remained paramagnetic down to 2 K. This dominant antiferromagnetic coupling is attributed to the carboxylate bridges. The ferromagnetic coupling expected due to the Mn-O(phenoxo)center dot center dot center dot Mn bridge plays an auxiliary role in the magnetic chain, but is an essential component of the bulk magnetic properties of the material.
Scientific journal, English - Structure and magnetic properties of an unprecedented syn-anti mu-nitrito-1 kappa O:2 kappa O ' bridged Mn(III)-salen complex and its isoelectronic and isostructural formate analogue
Paramita Kar; Rituparna Biswas; Michael G. B. Drew; Yumi Ida; Takayuki Ishida; Ashutosh Ghosh
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 40, 13, 3295-3304, Apr. 2011, Peer-reviwed, The preparation, crystal structures and magnetic properties of two new isoelectronic and isomorphous formate-and nitrite-bridged 1D chains of Mn(III)-salen complexes, [Mn(salen)(HCOO)](n) (1) and [Mn(salen)(NO2)](n) (2), where salen is the dianion of N,N'-bis(salicylidene)-1,2-diaminoethane, are presented. The structures show that the salen ligand coordinates to the four equatorial sites of the metal ion and the formate or nitrite ions coordinate to the axial positions to bridge the Mn(III)-salen units through a syn-anti mu-1 kappa O:2 kappa O' coordination mode. Such a bridging mode is unprecedented in Mn(III) for formate and in any transition metal ion for nitrite. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 indicate the presence of ferromagnetic exchange interactions with J values of 0.0607 cm(-1) (for 1) and 0.0883 cm(-1) (for 2). The ac measurements indicate negligible frequency dependence for 1 whereas compound 2 exhibits a decrease of chi(ac)' and a concomitant increase of chi(ac)'' on elevating frequency around 2 K. This finding is an indication of slow magnetization reversal characteristic of single-chain magnets or spin-glasses. The mu-nitrito-1 kappa O:2 kappa O' bridge seems to be a potentially superior magnetic coupler to the formate bridge for the construction of single-molecule/-chain magnets as its coupling constant is greater and the chi(ac)' and chi(ac)'' show frequency dependence.
Scientific journal, English - Biradical chelating host 2,2 '-bipyridine-6,6 '-diyl bis(tert-butyl nitroxide) showing tunable exchange magnetic coupling
Kazuya Koide; Takayuki Ishida
INORGANIC CHEMISTRY COMMUNICATIONS, ELSEVIER SCIENCE BV, 14, 1, 194-196, Jan. 2011, Peer-reviwed, The title compound was proposed as a paramagnetic host, and its chelation ability was confirmed by inclusion of a size-matching lanthanum(III) ion. The anti-configuration of the free ligand was changed to the syn configuration in the complex. The antiferromagnetic coupling was enhanced after complexation. In addition to the change of the intramolecular magnetic coupling, a superexchange mechanism is also assumed across the nitroxide-lanthanum(III)-nitroxide structure. (C) 2010 Elsevier B.V. All rights reserved.
Scientific journal, English - Chemical trend of Ln-M exchange couplings in heterometallic complexes with Ln = Gd, Tb, Dy, Ho, Er and M = Cu, V
Ryo Watanabe; Kei Fujiwara; Atsushi Okazawa; Go Tanaka; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 47, 7, 2110-2112, 2011, Peer-reviwed, The 4f-3d exchange couplings were definitively and precisely determined in the dinuclear complexes (Ln-M) involving double mu-oxo-bridges, by means of combined high-frequency electron paramagnetic resonance and pulsed-field magnetization techniques, revealing a monotonic decrease of ferromagnetic J(Ln-Cu) in the order of the atomic number, (64)Gd to (68)Er.
Scientific journal, English - Ferromagnetic Gd-Cu, Tb-Cu, and Ho-Cu Couplings in Isomorphous [Ln(2)Cu] Complexes
Atsushi Okazawa; Ryo Watanabe; Masaru Nezu; Takashi Shimada; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 39, 12, 1331-1332, Dec. 2010, Peer-reviwed, Exchange couplings in [{Ln(hfac)(3)}(2)Cu(dpk)(2)] (Hdpk stands for di 2-pyridyl ketoxime) were evaluated by high-frequency electron paramagnetic resonance and magnetization studies, showing ferromagnetic Ln-Cu couplings with J(Ln-Cu)/k(B) = +1 271(7), +0 405(3), and +0 196(13) K for Ln Gd Tb, and Ho, respectively
Scientific journal, English - Spin-Transition-Like Behavior on One Side in a Nitroxide-Copper(II)-Nitroxide Triad System
Atsushi Okazawa; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 49, 21, 10144-10147, Nov. 2010, Peer-reviwed, The ground spin-state of [Cu(phpyNO)(2)(H(2)O)(2)](BF(4))(2) was switched between S(total) = 1/2 and 3/2 across 175 K. On warming, the space group was changed from P2(1)2(1)2(1) to C222(1) in a single-crystal-to-single-crystal manner, and the transient structure could be monitored by means of the crystallographic analysis. The copper-radical exchange coupling changed from 2J/k(B) = -463(3) to +312(6) K with rather small Cu-O-N-C(2py) twisting deformation on one side, while practically no distortion occurred on the other.
Scientific journal, English - Ferro- and Antiferromagnetic Coupling Switch Accompanied by Twist Deformation around the Copper(II) and Nitroxide Coordination Bond
Atsushi Okazawa; Daisuke Hashizume; Takayuki Ishida
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 132, 33, 11516-11524, Aug. 2010, Peer-reviwed, Two novel copper(II) complexes with tert-butyl 2-pyridyl nitroxide (2pyNO(center dot)), [Cu(2+)(2pyNO(-))(2PyNO(center dot))](2)(BF(4)(-))(2)(1 center dot BF(4)) and [Cu(2+)(2pyNO(-))(2pyNO(center dot))](2)(ClO(4)(-))(2)(1 center dot ClO(4)), were prepared and structurally characterized. They contained mixed-valent ligands from 2pyNO, whose oxygen atoms were located at equatorial positions of the copper ion. The [Cu(2+)(2pyNO(-))(2pyNO(center dot))] unit was dimerized by mu-oxo bridges of the anion ligand, giving a zigzag linear spin system involving four paramagnetic S = 1/2 centers. The two compounds are isomorphous in an orthorhombic Pbca space group. Magnetic study revealed that 1 center dot ClO(4) showed ferromagnetic copper-radical coupling in all temperature ranges investigated here. On the other hand, 1 center dot BF(4) exhibited a structural phase transition at 64 K, where the magnetic susceptibility was drastically dropped on cooling. The copper-radical magnetic couplings were characterized as ferro- and antiferromagnetic for the high- and low-temperature phases, respectively. The crystallographic analysis clarified that the nitroxide oxygen atom remained at the equatorial position throughout the single-crystal-to-single-crystal phase transition, while the previously known spin-transition-like copper-radical compounds showed conversion of the roles of equatorial and axial positions. The orthogonal arrangement between the copper d sigma and nitroxide pi(star) orbitals is essential for the ferromagnetic coupling, and a slight dislocation of the radical oxygen atom from the chelate plane leads to violation of the orthogonal orbital arrangement, giving a practically diamagnetic low-temperature phase.
Scientific journal, English - Organic Two-Step Spin-Transition-Like Behavior in a Linear S=1 Array: 3 '-Methylbiphenyl-3,5-diyl Bis(tert-butylnitroxide) and Related Compounds
Hirokazu Nishimaki; Takayuki Ishida
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 132, 28, 9598-9599, Jul. 2010, Peer-reviwed, The title compound showed a unique low-dimensional array with S = 1 molecules. The intermolecular antiferromagnetic coupling and intramolecular ferromagnetic coupling are simultaneously present, and accordingly, the S = 1/2 state appeared at 230-350 K between the diamagnetic phase and the paramagnetic S = 1 phase. The solid solid phase transition occurred in a single-crystal-to-single-crystal manner. The corresponding 3'-methoxy derivative is also presented for comparison.
Scientific journal, English - Hard Magnets after Freezing of Spin Dynamics of Soft Magnets in Cobalt(II)-Radical Chain Compounds
Yoshitomo Okamura; Norio Ishii; Takashi Nogami; Takayuki Ishida
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 83, 6, 716-725, Jun. 2010, Peer-reviwed, Several metal-radical alternating chains ([Co(hfac)(2)(CnPNN)]) were prepared, and their crystal structures and magnetic properties were systematically studied, where C-n-PNN stands for a phenylnitronyl nitroxide ligand having a linear C-n alkoxy group at the ortho or para position. X-ray crystal structure analysis was successfully performed for [Co(hfac)(2)(p-C5PNN)] (p-5). The chain structure is similar to those of the known p-butoxy and o-ethoxy derivatives. Compound p-5 showed a very large coercive field of 51 kOe (4.1 MA m(-1)) and a saturation magnetization of 9.7 x 10(3) erg Oe(-1) mol(-1) at 6 K. o-Propoxy and o-pentoxy derivatives also exhibited large coercive fields of 50-54 kOe at 5-6 K. The activation energies of magnetization reorientation for the present compounds were estimated to be as large as 290-360 K from Arrhenius analysis using ac susceptibility data. In a temperature range of ca. 10-40 K, all of the present compounds behaved as very soft magnets, as indicated by no hysteresis in the ferromagnetic M-H curves. We propose a mechanism for the drastic soft-hard switch. The hard character grows immediately after freezing of the spin dynamics owing to the strong magnetic anisotropy.
Scientific journal, English - Amino Acid Spin Labels. An Application of Chelation Ability to a Nickel(II) Ion
Sayaka Osada; Kazuki Igarashi; Takashi Nogami; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 39, 6, 576-577, Jun. 2010, Peer-reviwed, NN-CH2-substituted L-alanine methyl ester (NNCH2-L-Ala-OMe) and beta-alanine ethyl ester (NNCH2-beta-Ala-OEt) were prepared, where NN stands for 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide. Their nickel(II) perchlorate complexes with a metal/ligand ratio of 1/2 were structurally and magnetically characterized.
Scientific journal, English - Super-superexchange coupling through a hydrogen bond in a linear copper(II) complex, [Cu(LH)(L)]center dot BF4 center dot 2H(2)O (LH = N-tert-butyl-N-2-pyridylhydroxylamine)
Atsushi Okazawa; Takayuki Ishida
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 480, 4-6, 198-202, Oct. 2009, Peer-reviwed, Crystal structure analysis of the title compound revealed the presence of a hydrogen bond in an intermolecular LH center dot center dot center dot L contact with the O center dot center dot center dot O distance of 2.4252(16) angstrom to form a one-dimensional polymeric structure. Magnetic study clarified that a relatively large exchange coupling was determined as 2J/k(B) = -33.2(2) K from the Bonner-Fisher analysis and ascribable to the super-superexchange coupling along the Cu-O-H center dot center dot center dot O-Cu path. (C) 2009 Elsevier B.V. All rights reserved.
Scientific journal, English - Long-Range Order in the One-Dimensional Cobalt(II)-Radical Coordination Polymer Magnet Probed by Muon-Spin Rotation and Relaxation
Takayuki Ishida; Yoshitomo Okamura; Isao Watanabe
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 48, 15, 7012-7014, Aug. 2009, Peer-reviwed, A long-range-ordered state of CoBPNN was characterized by mu SR. The temperature at the depolarization rate divergence (40 K) is defined as a magnetic transition temperature (T-N). The phase is unique below T-N, but gradual freezing of the domain-wall motion finally leads to the magnetically hard character.
Scientific journal, English - The Hardest Magnet from a Coordination Polymer of Alternating Cobalt(II)-Radical Heterospins
Yoshitomo Okamura; Takashi Nogami; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 38, 7, 740-741, Jul. 2009, Peer-reviwed, A coordination polymer [Co(hfac)(2)center dot L] (L = o-ethoxyphenyl nitronyl nitroxide) was prepared, structurally characterized, and revealed to show a record coercive field of 54 kOe at 6 K. The magnetic easy axis was found to be perpendicular to the chain direction. Interchain dipolar coupling is important for the bulk and/or single-chain properties in this series.
Scientific journal, English - Ferromagnetic coupling of copper(II) and nickel(II) complexes with a cyclam-based paramagnetic host
Kazuki Igarashi; Takashi Nogami; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 28, 9-10, 1672-1677, Jun. 2009, Peer-reviwed, Bis(NN-CH(2))-substituted dimethylcyclam (cyclamNN(2)) was designed and synthesized as a paramagnetic host, where NN stands for 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide. We prepared transition-metal complexes [M(cyclamNN(2))](ClO(4))(2) (M = Cu (1), Ni (2)) and investigated their metal-radial exchange couplings. The copper ion in 1 is located at the center of the cyclam cavity and one radical arm is coordinated at an axial position. Compound 1 showed ferromagnetic coupling (2J/k(B) = +44(3) K), which is ascribable to the NN-Cu coupling. Ferromagnetic coupling was also observed in 2 but the molecular structure was, unknown at present. The Curie-Weiss analysis gave the Weiss temperature (theta) of +13.5(6) K for 2. (C) 2008 Elsevier Ltd. All rights reserved
Scientific journal, English - Strong intramolecular ferromagnetic couplings in nickel(II) and copper(II) complexes chelated with tert-butyl 5-methoxy-2-pyridyl nitroxide
Atsushi Okazawa; Takashi Nogami; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 28, 9-10, 1917-1921, Jun. 2009, Peer-reviwed, We successfully isolated a new paramagnetic bidentate ligand tert-butyl 5-methoxy-2-pyridyl nitroxide (meopyNO). Complexation of nickel(II) and copper(II) perchlorates with meopyNO gave the corresponding ML(2)-type bis-chelated compounds. The magnetic studies showed that they were ground high-spin molecules with 2J/k(B) = +288(5) and +178(3) K for [M(meopyNO)(2)(H(2)O)(2)]center dot(ClO(4))(2) (M = Ni and Cu, respectively), where the spin Hamiltonian is defined as H = -2J(S(1)center dot S(2) + S(2)center dot S(3)). From the crystallographic analysis, the torsion angles (phi) around M-O-N-C(2py) were 4.2(3)degrees and 6.87(19)degrees, respectively, being so small that the orthogonality between the magnetic radical pi* and the metal d sigma orbitals would be guaranteed. (C) 2008 Elsevier Ltd. All rights reserved.
Scientific journal, English - Magnetic properties and exchange couplings of one-dimensionally arrayed 4f-3d heterometallic [Ln(2)Cu(2)](n) compounds
Atsushi Okazawa; Ryo Watanabe; Hiroyuki Nojiri; Takashi Nogami; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 28, 9-10, 1808-1813, Jun. 2009, Peer-reviwed, Heterometallic polymeric coordination compounds [{Ln(hfac)(2)(CH3OH)}(2){Cu(dmg)(Hdmg)}(2)](n) ([Ln(2)Cu(2)](n); Ln = Tb, Ho, and Er; H(2)dmg = dimethylglyoxime; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) were synthesized, and the X-ray crystallographic analysis shows that their structures are isomorphous to those of the known ferrimagnetic [Gd2Cu2](n) and [Dy2Cu2](n) analogs. The exchange couplings in [Tb2Cu2](n), [Ho2Cu2](n), and [Er2Cu2](n) were precisely evaluated by high-frequency EPR and pulsed-field magnetization studies, giving J(Tb-Cu)/k(B) = -0.77(2)K, J(Ho-Cu)/k(B) = -0.250(12)K and J(Er-Cu)/k(B) = -0.149(15) K. They were comparable to those of the Gd and Dy analogs. The absolute value of the exchange coupling parameter monotonically decreases in the order of Gd, Tb, Dy, Ho, and Er. (C) 2008 Elsevier Ltd. All rights reserved.
Scientific journal, English - Structures and magnetic properties of imidazolate-bridged tetranuclear and polymeric copper(II) complexes
Nobumasa Koyama; Ryo Watanabe; Takayuki Ishida; Takashi Nogami; Tamizo Kogane
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 28, 9-10, 2001-2009, Jun. 2009, Peer-reviwed, Eight kinds of imidazolate-bridged copper(II) complexes were found to be classified into two categories from the magnetic properties. The crystal structures of [Cu(L)(mu-im)](n) (Him = imidazole; L = nonane-4,6-dionate, 2,6-dimethylheptane-3,5-dionate) and [Cu(L)(mu-im)](4) (L = nonane-4,6-dionate, 1-phenylbutane-1,3-dionate) were determined, to reveal that they consist of polymeric chains and tetranuclear cycles, respectively. Note that the nonane-4,6-dionate derivative gave the two phases. The Bonner-Fisher model (a one-dimensional antiferromagnetic chain model) was plausibly applied to [Cu(L)(mu-im)](n) for the best fit, while a square model was to [Cu(L)(mu-im)](4). The complexes with unknown crystal structures were also subjected to magnetic measurements, and the tetra- and polymeric structures could be clearly distinguished from each other by fitting the magnetic data to appropriate models. The exchange parameters were comparable for both series (2J/k(B) = -78 to -97 K) because the structurally common bridges Cu-N(eq)-N(eq)-Cu afford comparable magnitudes of couplings. (c) 2008 Elsevier Ltd. All rights reserved.
Scientific journal, English - Spin-crossover Transition in a Mesophase Iron(II) Thiocyanate Complex Chelated with 4-Hexadecyl-N-(2-pyridylmethylene)aniline
Yuya Oso; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 38, 6, 604-605, Jun. 2009, Peer-reviwed, The title compound was a high-spin molecule for a morph as synthesized but exhibited a spin-crossover transition at 176 K in its mesophase after annealing above the mesophase transition at 353 K. The hexyl derivative in place of the hexadecyl group showed a reversible spin-crossover at 117 K, while the unsubstituted derivative had a sturdy high-spin state.
Scientific journal, English - Ferromagnetic Dy-Ni and Antiferromagnetic Dy-Cu Couplings in Single-Molecule Magnets [Dy2Ni] and [Dy2Cu] (vol 47, pg 9763, 2008)
Atsushi Okazawa; Takashi Nogami; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 48, 7, 3292-3292, Apr. 2009, Peer-reviwed
Scientific journal, English - Ferromagnetic Superexchange Coupling through a Diamagnetic Iron(II) Ion in a Mixed-Valent Iron(III, II, III) meso-Helicate
Toshihide Mochizuki; Takashi Nogami; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 48, 5, 2254-2259, Mar. 2009, Peer-reviwed, meso-Helicates [Ni(3)(pzNTR)(6)]center dot 4CH(3)CN and [Fe(3)(pzNTR)(6)](ClO(4))(2) center dot CH(3)OH were prepared (HpzNTR stands for N-tert-butyl-alpha-3-pyrazolylnitrone). The former showed antiferromagnetic coupling between neighboring ions with J/k(B) = -28.2(2) K, which can be reasonably interpreted in terms of the superexchange mechanism. On the other hand, the latter exhibited ferromagnetic coupling with J/k(B) = +0.292(8) K between the two terminal S = 5/2 Fe(3+) ions through the intervening diamagnetic Fe(2+) ion. The admixture of low-lying excited states with the ground state stabilizes the ferromagnetically coupled state, like the Prussian blue magnet.
Scientific journal, English - Crystal Structures and Magnetic Properties of Two Phases from Imidazolate-bridged Copper(II) 4,6-Nonanedionate Complexes
Ryo Watanabe; Nobumasa Koyama; Takashi Nogami; Takayuki Ishida; Tamizo Kogane
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 38, 1, 30-31, Jan. 2009, Peer-reviwed, A helical chain [Cu(dnbm)(mu-im)](n) and a tetrancuclear macrocycle [Cu(dnbm)([mu-im)](4) (Hdnbm = 4,6-nonanedione, Him = imidazole) were selectively prepared and structurally characterized. Their magnetic properties obeyed one-dimensional] chain and square models, respectively.
Scientific journal, English - Ferromagnetic Dy-Ni and Antiferromagnetic Dy-Cu Couplings in Single-Molecule Magnets [Dy2Ni] and [Dy2Cu]
Atsushi Okazawa; Takashi Nogami; Hiroyuki Nojiri; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 47, 21, 9763-9765, Nov. 2008, Peer-reviwed, The exchange couplings in [{Dy(hfac)(3)}(2)Cu(dpk)(2)] and [{Dy(hfac)(3)}(2)-Ni(dpk)(2)(py)(2)] (Hdpk = di-2-pyridyl ketoxime) were precisely evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving J(Dy-Cu)/k(B) = -0.126 K and J(Dy-Ni)/k(B) = +0.031 K.
Scientific journal, English - Magneto-structure relationship in copper(II) and nickel(II) complexes chelated with stable tert-butyl 5-phenyl-2-pyridyl nitroxide and related radicals
Atsushi Okazawa; Yasunori Nagaichi; Takashi Nogami; Takayuki Ishida
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 47, 19, 8859-8868, Oct. 2008, Peer-reviwed, We have isolated and characterized a new paramagnetic bidentate ligand, tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO). The spin distribution onto the pyridine ring was clarified from the Electron Spin Resonance spectrum. Complexation of phpyNO with nickel(II) and copper(II) ions gave ML2-type chelated compounds. The magnetic measurements of [Ni(phpyNO)(2)(H2O)(2)]center dot(ClO4)(2) and [Cu(phpyNO)(2)(H2O)]center dot(ClO4)(2)center dot C6H4Cl2 revealed that the metalradical exchange couplings were ferromagnetic with 2J/k(B) = +409(10) and +434(12) K, respectively. The torsion angle (phi) around M-O-N-C-2py can be regarded as a reliable indicator for the plane geometry of chelates; namely, highly planar chelates defined by small phi exhibit ferromagnetic coupling. An approximate linear relation. was found in the J versus phi plot using the data of the present complexes and. related known compounds. The critical angle of phi, at which the sign of the metal-radical exchange changes from positive to negative, was 12.6(9)degrees. This finding could be almost reproduced by density-functional theory calculation on a model copper(II)-nitroxide dyad. The exchange couplings in equatorially coordinated copper(II)- and nickel(II)-nitroxide complexes are very strongly ferromagnetic by nature.
Scientific journal, English - A pyrazine-bridged linear pentanuclear copper(II) complex and related tri- and dinuclear complexes showing various coordination structures and magnetic couplings
Nobumasa Koyama; Takayuki Ishida; Takashi Nogami; Tamizo Kogane
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 27, 11, 2341-2348, Aug. 2008, Peer-reviwed, Sterically bulky pyrazines have been successfully utilized for the preparation of discrete oligo-nuclear TBP (trigonal bipyramidal), SqP (square pyramidal), and Oh (octahedral) copper(II) complexes. We have synthesized a unique linear pentanuclear complex [{Cu(hfac)(2)}(5)(mu-2-butyl-3-methylpyrazine)(4)]. The two terminal copper(II) ions have a SqP structure while the three inner ions have an Oh one. The solvent molecule was incorporated in the clearance of the lattice. From another reaction under harsh conditions, we separated [{Cu(hfac)(2)}(3)(mu-2-butyl-3-metllylpyrazine)(2)], which can be regarded as the central moiety of the pentanuclear one. We also prepared a dinuclear complex [{Cu(hfaC)(2)}(2)(mu-tetramethylpyrazine)], in which the pyrazine nitrogen atoms were located at TBP equatorial positions. Single-crystal EPR measurements supported its compressed TBP structure. The exchange coupling was antiferromagnetic with J(TBP-TBP)/k(B) = -3.6 K. The linear trinuclear [{Cu(hfac)(2)}(3)(mu-2,3,5-trimethylpyrazine)(2)], having two TBP Cu ions with an intervening Oh Cu ion, showed very weak antiferromagnetic coupling. DFT calculations on these compounds indicated that the sigma-type orbital overlap between the Cu and N atoms is essential for superexchange interactions. (C) 2008 Elsevier Ltd. All rights reserved.
Scientific journal, English - Spin-crossover transition coupled with another solid-solid phase transition for iron(II) thiocyanate complexes chelated with alkylated N-(di-2-pyridylmethylene)anilines
Yuya Oso; Daisuke Kanatsuki; Shuichi Saito; Takashi Nogami; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 37, 7, 760-761, Jul. 2008, Peer-reviwed, We have prepared spin-crossover [FeL2(NCS)(2)] complexes chelated with alkylated N-(di-2-pyridylmethylene)anifines. The wider irreversible thermal loop across room temperature was observed with the longer alkyl chain introduced (Delta T-C = ca. 90 K for a n-C16H33 derivative). Pressurization prohibits the solid-solid phase transition, leading to the reversible spin crossover.
Scientific journal, English - Exchange coupling and energy-level crossing in a magnetic chain [Dy2Cu2](n) evaluated by high-frequency electron paramagnetic resonance
Atsushi Okazawa; Takashi Nogami; Hiroyuki Nojiri; Takayuki Ishida
CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, 20, 9, 3110-3119, May 2008, Peer-reviwed, A 4f - 3d heterometallic polymeric coordination compound [[Dy(hfac)(2)(CH3OH)}(2)(Cu(dmg)(Hdmg)(2)}](n) [ (Dy2Cu](n) Hdmg = dimethylglyoxime; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) was synthesized, and the X-ray crystallographic analysis shows that the structure is isomorphous to the known ferrimagnetic [Gd2Cu2)](n) polymer. A centrosymmetric diamond-arrayed ferrimagnetic unit involving the oximate bridge, Dy - O - N - Cu, is repeated to form a discrete chain. An onset of the frequency dependence was found in the ac magnetic susceptibility measurements down to 1.8 K. Low-temperature magnetization measurements on [Dy2Cu2](n) exhibited magnetic hysteresis with magnetization steps. To examine the energy level structure and the exchange coupling between the Dy and Cu ions, high-frequency EPR (HF-EPR) spectra of a polycrystalline sample of [Dy2Cu2](n) were recorded at various frequencies (34.7 - 525.4 GHz) and temperatures. We analyzed the spectra by treating the Dy moments as Ising spins and built an exchange-coupling model for a diamond-arrayed tetranuclear macrocycle [Dy2Cu2]. The Dy - Cu exchange couplings were precisely evaluated, owing to the high resolution of HF-EPR; J/k(B) = - 0.895(8) and - 0.061(8) K for two independent Dy - Cu relations, where the exchange parameter is defined as - J. The Cu center dot center dot center dot Cu coupling among the macrocycles was estimated to be ferromagnetic with approximately 1 K. The present study has established the definitive methodology to examine the energy level in 4f - 3d heterometallic systems by using HF-EPR. The magnetic properties of the [Dy2Cu2](n) chain were plausibly described as a perturbed system of a single-molecule magnet. The quantum tunneling of the magnetization is based on a different principle compared with those of the 3d-based single-molecule magnets, since the energy level structure of [Dy2Cu2](n) is regulated by the exchange couplings.
Scientific journal, English - Giant coercivity in a one-dimensional cobalt-radical coordination magnet
Norio Ishii; Yoshitomo Okamura; Susumu Chiba; Takashi Nogami; Takayuki Ishida
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 130, 1, 24-+, Jan. 2008, Peer-reviwed, A metal-radical polymer (Co(hfac)(2) BPNN] showed a very large coercive field of 52 kOe (4.1 MA m(-1)) at 6 K, indicating that it is the hardest magnet ever reported. Above 10 K, a soft character appeared, owing to the fast dynamics of magnetization reorientation.
Scientific journal, English - Mono- and dinitroxide radicals from 9,9 '(10H,10 ' H)-spirobiacridine: An approach to a D-2d triplet biradical
Takayuki Ishida; Motohiro Ooishi; Norio Ishii; Hironori Mori; Takashi Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 26, 9-11, 1793-1799, Jun. 2007, Peer-reviwed, Oxidation of 9,9 '(10H,10 ' H)-spirobiacridine with m-chloroperbenzoic acid gave a dinitroxide biradical derivative, SBDO, together with a monoradical, SBO. Their molecular and crystal structures were determined by X-ray crystallographic analysis. Magnetic measurements on a polycrystalline sample of SBDO revealed the presence of dominant antiferromagnetic interaction, which can be ascribed mainly to intermolecular interaction due to close contacts between two nitroxide groups. The intermolecular N-O distances were 3.176(2) and 3.184(2) angstrom. The diluted ESR experiments and the DFT calculation on a single molecule of SBDO indicated the ground triplet state. We also found that SBO worked as a versatile host for organic solvent molecules (CH2Cl2, CHCl3, CH3CN, ClC6H5, CH3OH, etc.). (c) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English - Structures and magnetic properties of one-dimensional copper(II) complexes bridged with diazaaromatic rings
Tamizo Kogane; Nobumasa Koyama; Takayuki Ishida; Takashi Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 26, 9-11, 1811-1819, Jun. 2007, Peer-reviwed, Seven kinds of polynuclear complexes of [Cu(hfac)(2)] (Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) with diazaaromatic rings have been prepared. The crystal structures of [{Cu(hfac(mu-L)}(n)] (L = 2,5- and 2,6-dimethylpyrazines, propylpyrazine (prpyz), quinoxaline, phenazine, 4,6-dimethylpyrimidine, and 1,6-naphthyridine) have been determined. These complexes consist of a one-dimensional chain structure, and the geometry around the copper ion is approximately an octahedral structure. The relations between the magnetic properties and coordination structure were discussed from the magnetic measurements. In the mu-prpyz complex, one nitrogen atom is coordinated to a copper ion at an axial position, and at the same time the other coordinated at an equatorial site of a neighboring copper ion. This complex showed antiferromagnetic interaction with J/k(B) = -0.086(3) K estimated from the Bonner-Fisher model. Weak magnetic interaction is caused by the somewhat long Cu-N distances due to the steric effect from the bridging ligands. (c) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English - Tetranuclear heterometallic cycle Dy2Cu2 and the corresponding polymer showing slow relaxation of magnetization reorientation
Sohei Ueki; Atsushi Okazawa; Takayuki Ishida; Takashi Nogami; Hiroyuki Nojiri
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 26, 9-11, 1970-1976, Jun. 2007, Peer-reviwed, We prepared tetranuclear complexes [{Cu(emg)(Hemg)(ROH)}(2)Dy(hfac)(2)(ROH)}(2)] (abbreviated as [Dy2Cu2]-R; R = Me, Et; H(2)emg=ethylmethylglyoxime) and the corresponding polymer [{Cu(dmg)(Hdmg)}(2){Dy(hfac)(2)(CH3OH)}(2)](n) center dot 2(MeOH) ([Dy2Cu2](n); H(2)dmg = dimethylglyoxime), which were characterized as analogs of the known [Gd2Cu2] monomer and polymer, respectively, by means of X-ray crystallographic analysis. The M-H curves clarified antiferromagnetic coupling between Dy and Cu in the [Dy2Cu2] motif, leading to the Dy magnetic moments aligned parallel ([Cu(down arrow)Dy(up arrow)Cu(down arrow)Dy(up arrow)]). Ac magnetic susceptibility measurements of [Dy2Cu2]-Me and [Dy2Cu2](n), exhibited a chi(ac)' (in-phase) decrease and a concomitant chi('')(ac) (out-of-phase) increase with an increase of frequency. Low-temperature magnetization measurements on [Dy2Cu2], exhibited magnetic hysteresis, which is characteristic of single-chain magnets. (c) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English - Preparation, structures, and magnetic properties of precursors for chelating compounds of 2-pyridyl nitroxide derivatives
Atsushi Okazawa; Takashi Nogami; Takayuki Ishida
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 26, 9-11, 1965-1969, Jun. 2007, Peer-reviwed, We successfully synthesized and characterized two precursors for paramagnetic chelating ligands, N-p-anisyl-N-2-pyridylhydroxyl-amine and 2,6-bis(N-t-butylhydroxylamino)pyridine. The former can be regarded as a rare case since N,N-diarylhydroxylamines cannot be isolated in general because of facile autoxidation. The oxidation with silver(I) oxide gave radicals showing typical nitroxide ESR signals, but the resultant radicals were unstable under ambient conditions. Theoretical DFT calculation indicated that the bisnitroxide radical, pyridine-2,6-diyl bis(t-butyl nitroxide), had a triplet ground state. (c) 2006 Elsevier Ltd. All rights reserved.
Scientific journal, English - Quantum tunneling of magnetization via well-defined Dy-Cu exchange coupling in a ferrimagnetic high-spin [Dy4Cu] single-molecule magnet
Sohei Ueki; Takayuki Ishida; Takashi Nogami; Kwang-Yong Choi; Hiroyuki Nojiri
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 440, 4-6, 263-267, Jun. 2007, Peer-reviwed, A centrosymmetric rectangular complex [DY4Cu] was prepared from dysprosium(III) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and copper(II) dimethylglyoximate. From magnetic studies, the Dy magnetic moments are all aligned parallel at the ground state via anti-ferromagnetic superexchange interaction with the central Cu spin. In pulsed-field magnetization measurements at 0.5 K, complex [DY4Cu] exhibited magnetization steps with hysteresis, which is typical of a single-molecule magnet. This behavior is explained in terms of a simple Ising model together with well-defined Dy-Cu exchange coupling (-0.64 K). (C) 2007 Elsevier B.V. All rights reserved.
Scientific journal, English - tert-butyl 2-pyridyl nitroxide available as a paramagnetic chelate ligand for strongly exchange-coupled metal-radical compounds
Atsushi Okazawa; Takashi Nogami; Takayuki Ishida
CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, 19, 11, 2733-2735, May 2007, Peer-reviwed
Scientific journal, English - Magnetic exchange coupling tunable by means of selective cation binding into poly(radical-armed) azacrowns
Kazuki Igarashi; Takashi Nogami; Takayuki Ishida
CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 2007, 5, 501-503, 2007, Peer-reviwed, Host - guest complexes of tris(NN - CH2)-substituted 1,4,7-triazacyclononane and tetrakis( NN - CH2)- substituted 1,4,7,10-tetraazacyclododecane afforded the folded structures of the hosts where the NN radical oxygen atoms were coordinated to the guest metal ion, leading to enhanced antiferromagnetic couplings in the solid state and an ESR line broadening in the solution phase (NN = 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide).
Scientific journal, English - Strong ferromagnetic exchange couplings in copper(II) and nickel(II) complexes with a paramagnetic tridentate chelate ligand, 2,2 '-bipyridin-6-yl tert-butyl nitroxide
Keita Osanai; Atsushi Okazawa; Takashi Nogami; Takayuki Ishida
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 128, 43, 14008-14009, Nov. 2006, Peer-reviwed
Scientific journal, English - Bistable polymorphs showing diamagnetic and paramagnetic states of an organic crystalline biradical biphenyl-3,5-diyl bis(tert-butylnitroxide)
Hirokazu Nishimaki; Shinichiro Mashiyama; Masanori Yasui; Takashi Nogami; Takayuki Ishida
CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, 18, 16, 3602-3604, Aug. 2006, Peer-reviwed
Scientific journal, English - Ferromagnetic exchange coupling in a spiro-fused dinuclear nickel(II) complex with an approximate D-2d symmetry
Atsushi Okazawa; Takashi Nogami; Takayuki Ishida
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 427, 4-6, 333-337, Aug. 2006, Peer-reviwed, Ferromagnetic exchange coupling was operative between nickel(II) spins in a dinuclear nickel(II) complex [{Ni(hfac)(2)}(2)(py(4)C)] with J/k(B) = +0.57(2)K (H = -2JS(1) . S-2), where hfac and py(4)C Stand for 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and tetrakis(2-pyridyl)methane, respectively. X-ray crystal structure analysis revealed an approximate D-2d symmetry of the [Ni(py4C)Ni] core and accordingly the orthogonal arrangement between the two coordination basal planes. Mechanism of the ferromagnetic coupling was proposed on the basis of the orthogonal d sigma-type magnetic orbitals, which was supported by DFT calculation. (c) 2006 Elsevier B.V. All rights reserved.
Scientific journal, English - Illumination-induced magnetization enhancement of the weak ferromagnet [Fe(N-3)(2)(pm)] (pm = pyrimidine)
Yasuhiko Morishita; Yoshitaka Doi; Takashi Nogami; Takayuki Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 35, 7, 770-771, Jul. 2006, Peer-reviwed, The spontaneous magnetization of [Fe(N-3)(2)(pm)] (pm = pyrimidine) was enhanced after UV illumination while the spin-canted antiferromagnetic transition temperature (39K) was unchanged. Azide-bridged two-dimensional network was damaged on illumination as clarified by IR measurements, possibly leading to an increase of the cant angle.
Scientific journal, English - Polymorphic alternating HNN-cobalt(II) chains both behaving as single-chain magnets (HNN=4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide)
N Ishii; T Ishida; T Nogami
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 45, 10, 3837-3839, May 2006, Peer-reviwed, Metal-radical alternating chains [Co(hfac)(2)HNN](n) crystallized in two morphs containing repeating all-cis (alpha) and cis, cis, trans (beta) configurations with respect to the O-HNN-Co-O-HNN geometry (HNN = 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide). Both phases showed magnetization jumps with hysteresis at 2 K. The R phase has a relatively high activation energy of magnetization reorientation (193 K).
Scientific journal, English - Self-assembled meso-helicates of linear trinuclear nickel(II)-radical complexes with triple pyrazolate bridges
S Yamada; M Yasui; T Nogami; T Ishida
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 2006, 13, 1622-1626, Apr. 2006, Peer-reviwed, Complexation of 3-nitronyl-nitroxide-substituted pyrazolate (pzNN) and 3-imino-nitroxide-substituted pyrazolate (pzIN) with nickel(II) gave [Ni-3(pzNN)(6)] and [Ni-3(pzIN)(6)], respectively They were practically isomorphous and characterized as a linear trinuclear structure with neighboring nickel ions triply bridged by pyrazolate moieties. The space groups were P2(1)/n but the molecules have a pseudo three-fold axis. We found polymorphs in the crystals of [Ni-3(pzIN)(6)] depending on the solvate molecules; another space group was a cubic Pa (3) over bar. The opposite chirality around the inversion center at the central nickel(II) ion leads to a meso-helical symmetry in the whole molecule. The radical oxygen atoms participate in the 6-membered chelation at the terminal nickel(II) ions. Antiferromagnetic couplings were observed in both complexes, which are ascribable to interactions between the nickel and radical spins and between the nickel spins across the pyrazolate bridges.
Scientific journal, English - Bio-inspired materials for electron donors and charge-transfer complex formation based on the imidazopyrazinone luciferin core
M Suzuki; T Fujii; T Nogami; T Hirano; T Ishida
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 35, 3, 250-251, Mar. 2006, Peer-reviwed, The electron-donating properties of 2-phenyl- and 2-methylimidazo[1,2-a]pyrazin-3(7H)-ones were confirmed by the oxidation potentials. The I/I molecular complex from the former and TCNQ was characterized by means of X-ray crystallographic analysis, and the charge-transfer degree was estimated to be 16% from the IR nitrile stretching bands.
Scientific journal, English - Oximate-bridged trinuclear Dy-Cu-Dy complex behaving as a single-molecule magnet and its mechanistic investigation
F Mori; T Nyui; T Ishida; T Nogami; KY Choi; H Nojiri
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 128, 5, 1440-1441, Feb. 2006, Peer-reviwed
Scientific journal, English - ET and TTF salts with lanthanide complex ions showing frequency-dependent ac magnetic susceptibility
Sohei Ueki; Takashi Nogami; Takayuki Ishida; Masafumi Tamura
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 455, 129-134, 2006, Peer-reviwed, We measured conducting and magnetic properties of (ET)(4)[Ln(NCS)(6)](CH2Cl2)-C-. (Ln = Dy, Ho, Er, and Yb), (ET)(5)[Ln(NCS)(6)NO3](EtOH)-Et-. (Ln = Tb and Dy), and (TTF)6[Dy(NCS)6]. All of the complexes behaved as semiconductors irrespective of Ln ions used, and also exhibited anomalous frequency-dependence of ac magnetic susceptibility below ca. 10 K, especially for Dy derivatives, indicating blocking behavior as found in single-molecule magnets.
Scientific journal, English - Double half-cubane copper(II) complexes available from copper(II) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate dissolved in formamides
Yasuhiko Morishita; Tamizo Kogane; Takashi Nogami; Takayuki Ishida
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 2006, 37, 4438-4443, 2006, Peer-reviwed, Tetranuclear copper(II) complexes were obtained after simply dissolving [Cu(hfac)(2)] in formamide - methanol mixed solvents (Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione). X-Ray diffraction studies revealed that they possessed a tetranuclear double half-cubane core sandwiched with two trianionic ligands from 2,4,6-tris(trifluoromethyl) tetrahydropyran-2,4,6-triol (H(3)ttpt). Complexes [Cu-4(ttpt)(2)(hfac)(2)(dmf)(2.5)], [Cu-4(ttpt)(2)(tfa)(2)(def)(4)], and [Cu-4(ttpt)(2)(hfac)(2)(H2O)(4)]( fa) were prepared from N,N-dimethylformamide(dmf) - MeOH, N, N-diethylformamide (def) -MeOH, and formamide(fa) - MeOH (Htfa = trifluoroacetic acid), respectively. A possible mechanism is proposed where a templated aldol-type reaction takes place between hfac and 1,1,1-trifluoroacetonate. Magnetic measurements revealed the presence of antiferromagnetic interaction in the Cu4O6 core.
Scientific journal, English - Magnetic properties of transition metal complexes with 2,2 '-bipyridin-5-yl t-butyl nitroxide
T Shimada; T Ishida; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 24, 16-17, 2593-2598, Nov. 2005, Peer-reviwed, Complexes [Mn-11(5bpno)(3)(ClO4)(2)], [Mn-11(5bpno)(CH3OH)(2)Cl-2], [Cu-11(5bpno)(2)(ClO4)(2)], and [Cu-11(5bpno)Cl-2] were prepared, where 5bpno stands for 2,2'-bipyridin-5-yl t-butyl nitroxide. X-ray crystallographic analysis clarified that the Cu ion in [Cu(5bpno)(2)(ClO4)(2)] was tetra-coordinate with four nitrogen atoms forming two chelate rings. Magnetic measurements revealed the presence of ferromagnetic couplings in the Mn complexes, whereas the Cu complexes showed antiferromagnetic Couplings. Magnetic exchange couplings between the metal and radical spins through the intervening pyridine ring can be explained in terms of the spin-polarization mechanism. (c) 2005 Elsevier Ltd. All rights reserved.
Scientific journal, English - Structure and magnetic properties of 3d-4f heterometallic complexes containing di-2-pyridyl ketoximate: An approach to single-molecule magnets
F Mori; T Ishida; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 24, 16-17, 2588-2592, Nov. 2005, Peer-reviwed, [{Ln(hfac)(3)}(2){Ni(dpk)(2)(phen)}] (1Ln) and [{Ln(hfac)(3)}(2){Ni(dpk)(2)(py)(2)}] (2Ln) were synthesized and characterized, where dpk = di-2-pyridyl ketoxmate and Ln = La, Tb, Dy, Ho, Er. The N-0 groups from dpk bridged the central nickel(11) ion and terminal lanthanicle(111) ions, giving a linear trinuclear array. Dc magnetic susceptibility measurements revealed that they did not possess appreciable intramolecular ferromagnetic or ferrimagnetic interaction. Ac magnetic susceptibility measurements clarified that frequency dependence of out-of-phase ac susceptibility was observed only for Dy derivatives 1Dy and 2Dy, which is regarded as an indication of single-molecule magnets. (c) 2005 Elsevier Ltd. All rights reserved.
Scientific journal, English - Structures and magnetic properties of copper(II) complexes containing tetrakis(2-pyridyl)methane
A Okazawa; T Ishida; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 24, 16-17, 2584-2587, Nov. 2005, Peer-reviwed, We designed spiro-fused dinculear complexes using tetrakis(2-pyridyl)methane (py(4)C) for the development of ground high-spin molecules. We attempted to prepare a dinuclear copper(II) complex [{Cu(hfac)(2)}(2)(py(4)C)], where hfac stands for 1, 1,1,5,5,5-hexafluoropentane-2,4-dionate, but we obtained [Cu(hfac)(2)(py(4)C)] and [Cu(hfac)(py(4)C) (.) Cu(hfac)(3)]. These molecular structures were determined by the X-ray crystal structure analysis. (c) 2005 Elsevier Ltd. All rights reserved.
Scientific journal, English - Trans-fused macrobicycle "betweenanene" around a planar Cu-2(mu-CH3O)(2) core showing remarkable antiferromagnetic interaction
T Ishisda; K Yanagi; T Nogami
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 44, 21, 7307-7309, Oct. 2005, Peer-reviwed, Complexation of 4,6-bis{3-(2-pyridyl)-1H-pyrazol-1-yl}pyrimidine (bppp) and copper(II) tetrafluoroborate in methanol gave a self-assembled [Cu-2(CH3O)(2)(bPPP)(2)](2+) ion having a betweenanene-type structure. Each bppp spans across the common Cu2O2 plane in a trans fashion to ligate each copper center. The antiferromagnetic interaction observed in the Cu2O2 core is ascribable to the superexchange along the Cu-O-Cu linkage and found to be one of the largest among the analogous compounds, owing to the large Cu-O-Cu angle perturbed with the two bppp molecular tweezers.
Scientific journal, English - Organic kagome lattice consisting of trimeric pyrazole and oxime supramolecular synthons from 3-pyrazolecarboxaldoxime
T Nyui; T Nogami; T Ishida
CRYSTENGCOMM, ROYAL SOC CHEMISTRY, 7, 612-615, Oct. 2005, Peer-reviwed, Crystallization of 3-pyrazolylaldoxime (H(2)pzao, 1) from chloroform gave a clathrate [ (H(2)pzao)(3) center dot CHCl3, 2] showing a 2-D structure where hydrogen-bonding supramolecular synthons of triangular NH center dot center dot center dot N and OH center dot center dot center dot N motifs are arranged alternately to form a hexagonal channel.
Scientific journal, English - Nano-sized tetralanthanoid-copper complex ions containing oximato bridges
S Ueki; M Sahlan; T Ishida; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 154, 1-3, 217-220, Sep. 2005, Peer-reviwed, Complexation of Ln(III)(hfac)(3), Ln(III)(OAc)(3), and [Cu-II(dmg)(2)](2-) in the presence of Ph4P+ gave [Ln(4)Cu(1)]-type pentanuclear complexes (dmg = dimethylglyoximate dianion; Ln = La, Nd, Eu, Gd, Tb). Single-crystal X-ray diffraction analyses revealed that four Ln(III) ions formed a rectangular array around the copper ion at its inversion center. The [Ln(4)Cu(1)] core structures are essentially the same regardless of the different Ln ions. From the magnetic susceptibility measurements, the Cu(dmg)(2) dianion moiety has been shown to play a role of the ferrimagnetic coupler among the Gd spins. The out-of-phase ac susceptibility of the [Tb4Cu1] complex exhibited anomalous frequency-dependence below 4 K, indicating blocking behavior potentially related to a single-molecule magnet.
Scientific journal, English - Pressure effect on the magnetic phase transition of guest-tunable weak ferromagnets [Fe{N(CN)(2)}(2) (pyrimidine)](guest) (Guest = ethanol and pyrimidine)
K Yuza; T Ishida; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 34, 7, 974-975, Jul. 2005, Peer-reviwed, The spontaneous magnetization of [Fe{N(CN)(2)}(2)(pm)]-(ethanol) (pm = pyrimidine) was suppressed under pressure up to 0.5 GPa and finally behaved as a paramagnet at 0.6 GPa. The loose packing of the host-guest complex structure seems responsible for the pressure-sensitive magnetism. On the other hand, [Fe{N(CN)(2)}(2)(pm)](pm) exhibited relatively small pressure dependence of the phase transition behavior.
Scientific journal, English - Structure and magnetic properties of a honeycomb-like copper(II) complex containing 4-aminopyrimidine and methoxide bridges
K Osanai; T Ishida; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 34, 4, 620-621, Apr. 2005, Peer-reviwed, Complexation of Cu(NO3)(2) with 4-aminopyrimidine (4APM) in methanol gave [Cu(4APM)(NO3)(OCH3)](n) which crystallizes in a trigonal space group R (3) over bar The three-dimensional network affords a tube-like cavity. Magnetic measurements revealed the presence of considerably large antiferromagnetic interaction due to the four-mernbered Cu2O2 structure.
Scientific journal, English - The first A(2)B(2)-heterometal ferrimagnetic chain. Structures and magnetic properties of polymeric [Gd2Cu2](n) and the corresponding monomer
S Ueki; Y Kobayashi; T Ishida; T Nogami
CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 2005, 41, 5223-5225, 2005, Peer-reviwed, One-dimensional polymeric complexes consisting of alternating dicopper(II) and digadolinium(III) units exhibited ferrimagnetic behavior which was ascribable to antiferromagnetic coupling across the oximate N-O bridges between the high-spin homodinuclear units.
Scientific journal, English - Effect of staggered field on the magnetization process of S=1/2 antiferromagnetic chains
A Matsuo; K Hosokawa; Y Narumi; K Okunishi; N Maeshima; T Asano; Y Ajiro; N Ishida; T Nogami; K Kindo
PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE, 159, 159, 158-162, 2005, Peer-reviwed, We measured the magnetization processes of the S = 1/2 antiferromagnetic chain compound, Cu benzoate. From the inelastic neutron scattering and the specific heat measurements it was recently discovered that the substance exhibits an unexpected gap which varies approximately as the 2/3 power of an applied magnetic field. The primary mechanism of the gap formation is produced by an effective staggered field due to both the alternating g-tensor and the Dzyaloshinskii-Moriya interaction. We observed the effect of the effective staggered field on the magnetization process of Cu benzoate as a rounding behavior near the saturation field as well as an initial nonlinear increment near zero field. The experimental results are well reproduced by the numerical calculation on the Hamiltonian which includes the appropriate term of the staggered field, using the finite temperature density matrix renormalization group method.
Scientific journal, English - Synthesis and characterization of dibenzodioxadiselenafulvalene
T Kojima; K Tanaka; T Ishida; T Nogami
JOURNAL OF ORGANIC CHEMISTRY, AMER CHEMICAL SOC, 69, 26, 9319-9322, Dec. 2004, Peer-reviwed, Dibenzodioxadiselenafulvalene (DBOSF) was prepared and the cis and trans isomers were separated. X-ray crystallographic analysis revealed the presence of Se---H and O---H hydrogen bonds in both crystals. The electrochemical properties of cis- and trans-DBOSFs together with dibenzotetraoxafulvalene (DBTOF) and cis- and trans-dibenzodioxadithiafulvalenes were investigated by means of cyclic voltammetry and DFT calculation. The electron-donating ability and the stability of oxidized forms of DBOSFs are improved compared with those of DBTOF.
Scientific journal, English - Dinuclear manganese(II) complex containing tetrakis(2-pyridyl)methane as a spiro-fused bridge
A Okazawa; T Ishida; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 33, 11, 1478-1479, Nov. 2004, Peer-reviwed, A dinuclear manganese(II) complex [{Mn(hfac)(2)}(2)(py(4)C)] was synthesized, where hfac and py(4)C denote 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and tetrakis(2-pyridyl)methane, respectively. X-Ray crystallographic analysis revealed that the dihedral angle was 87.4(2)degrees between two chelate rings around the spiro center. Very weak antiferromagnetic interaction is operative between manganese(II) spins.
Scientific journal, English - Magnetic coupling switch by means of host-guest chemistry in a polyether side-arm
T Nakabayashi; T Ishida; T Nogami
INORGANIC CHEMISTRY COMMUNICATIONS, ELSEVIER SCIENCE BV, 7, 11, 1221-1224, Nov. 2004, Peer-reviwed, Complexation from the polyether ligand (LH2), Ni(CH3CO2)(2), and Ba(CF3SO3)(2) gave BaNiL (.) 2CF(3)SO(3), which showed ferromagnetic coupling ascribable to the dimer structure determined by means of X-ray crystallographic analysis. After removal of Ba2+ by treatment with guanidinium sulfate, NiL was isolated as an empty host, which did not show ferromagnetic coupling. (C) 2004 Elsevier B.V. All rights reserved.
Scientific journal, English - Crystal structure of a molecular complex from native beta-cyclodextrin and copper(II) chloride
G Kurokawa; M Sekii; T Ishida; T Nogami
SUPRAMOLECULAR CHEMISTRY, TAYLOR & FRANCIS LTD, 16, 5, 381-384, Jul. 2004, Peer-reviwed, Reaction of beta-cyclodextrin (beta-CD) with CuCl2 in neutral aqueous solutions gave a stable molecular complex without any side-arm support. The X-ray crystallographic analysis clarified that the copper ion was located at the bottom of the primary-hydroxy side as a CuCl2(H2O)(2) form. Hydrogen bonds were found between the Cl and H2O ligands and beta-CD hydroxy and ether groups. The copper ion is axially coordinated with a hydroxy group of a neighboring beta-CD molecule, giving a one-dimensional beta-CD/CuCl2 array.
Scientific journal, English - Remarkably strong intermolecular antiferromagnetic couplings in the crystal of biphenyl-3,5-dlyl bis(tert-butyl nitroxide)
G Kurokawa; T Ishida; T Nogami
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 392, 1-3, 74-79, Jul. 2004, Peer-reviwed, Magnetic susceptibility measurements of biphenyl-3,5-diyl bis(t-butyl nitroxide) diradical showed practically diamagnetic behavior over a temperature range 1.8-300 K. The strong antiferromagnetic couplings are ascribable to intermolecular interactions whilst intramolecular coupling could not be observed. Partly bonding nature can be pointed out in the intermolecular N-O' contacts with the distances of 2.321(2) and 2.359(2) Angstrom, which are 23-24% shorter than the sum of the van der Waals radii. On the other hand, the N-O bond lengths of 1.303(2) and 1.294(2) Angstrom are somewhat longer than typical values of t-butyl phenyl nitroxide radicals reported. (C) 2004 Elsevier B.V. All rights reserved.
Scientific journal, English - Single-crystal magnetic study on guest-tunable weak ferromagnets [M{N(CN)(2)}(2)(pyrimidine)](guest) (M = Fe, Co)
N Takagami; T Ishida; T Nogami
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 77, 6, 1125-1134, Jun. 2004, Peer-reviwed, Low-temperature magnets derived from [M {N(CN)(2)}(2)(pm)] (M = Fe-II, Co-II) have guest molecules incorporated in the clearance of the three-dimensional framework, where pm stands for pyrimidine. A pm molecule in [Fe{N(CN)(2)}(2)(pm)](pm) (1) was characterized as a guest by means of X-ray crystallographic analysis. The guest molecules as well as the host N(CN)(2) skeletons are disordered in [Fe{N(CN)(2)}(2)(pm)](guest) (guest = EtOH (2), n-PrOH (3), 1/2 n-BuOH (4)) and also in [Co{N(CN)(2)}(2)(pm)] (guest) (guest = EtOH (5), n-PrOH (6)). The ac and dc magnetic susceptibility measurements on randomly oriented polycrystalline samples of 1-6 revealed that they were weak ferromagnets (canted antiferromagnets) below T-N. The single-crystal magnetization measurements clarified the T-N's and the cant angles at 2 K as follows: T-N = 5.6 K, theta = 1.3degrees (H parallel to c) for 1; T-N = 3.3 K, theta = 16degrees (H parallel to c) for 2; T-N = ca. 2 K, theta = 7.1degrees (H parallel to b) for 5. The magnetic ground state seems to be related with single-ion anisotropy of the metal ions and the spin canting may take place as a combined result of the axial or in-plane anisotropy and antiferromagnetic interaction. The incorporated guest molecule tunes the single-ion anisotropy of the host metal ions, and consequently the magnetic phase transition phenomena were drastically different depending on the guest molecules.
Scientific journal, English - High-field magnetization process in the S=1/2 chain [PM center dot Cu(NO3)(2)center dot(H2O)(2)](n) (PM = pyrimidine)
A Matsuo; Y Narumi; T Asano; Y Ajiro; T Ishida; T Nogami; K Kindo
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, ELSEVIER SCIENCE BV, 272, 1081-1082, May 2004, Peer-reviwed, We report the magnetization process on the S = 1/2 antiferromagnetic Heisenberg chain [PM . Cu(NO3)(2) . (H2O)(2)](n) (PM=pyrimidine). It has become clear that the staggered magnetic field plays an important role in the magnetic behavior from magnetic susceptibility and specific heat studies on single-crystalline samples. The magnetization curve for a single crystal of [PM . Cu(NO3)(2) . (H2O)(2)](n) does not show a divergent slope, but rounding behavior at the saturation field due to the effect of the staggered magnetic field even at 100mK. (C) 2004 Elsevier B.V. All rights reserved.
Scientific journal, English - ESR of quantum spin chains with staggered fields
T. Asano; Y. Ajiro; Y. Inagaki; H. Nojiri; T. Sakon; T. Ishida; T. Nogami; J. P. Boucher; M. Motokawa
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, ELSEVIER SCIENCE BV, 272, E685-E686, May 2004, Peer-reviwed, We study electron spin resonance (ESR) of S = 1/2 antiferromagnetic Heisenberg chain systems, Cu-benzoate and Cu-pyrimidine, with staggered fields caused by alternating g-tensor and Dzyaloshinskii - Moriya interaction. We observe clearly the effect of the staggered fields on the shift and the linewidth of ESR spectra. Especially, in Cu-benzoate, we reveal the field-induced gap and the quantum critical behavior as a dynamical crossover. (C) 2003 Elsevier B. V. All rights reserved.
Scientific journal, English - Weak ferromagnetism with very large canting in a chiral lattice: Fe(pyrimidine)(2)Cl-2
R Feyerherm; A Loose; T Ishida; T Nogami; J Kreitlow; D Baabe; FJ Litterst; S Sullow; HH Klauss; K Doll
PHYSICAL REVIEW B, AMERICAN PHYSICAL SOC, 69, 13, 134427/1-8, Apr. 2004, Peer-reviwed, The transition metal coordination compound Fe(pyrimidine)(2)Cl-2 crystallizes in a chiral lattice, space group I4(1)22 (or I4(3)22). Combined magnetization, Mossbauer spectroscopy, and powder neutron diffraction studies reveal that it is a canted antiferromagnet below T-N=6.4 K with an unusually large canting of the magnetic moments of 14degrees from their general antiferromagnetic alignment, one of the largest reported to date. This results in weak ferromagnetism with a ferromagnetic component of similar to1 mu(B). The large canting is due to the interplay between the antiferromagnetic exchange interaction and the local single-ion anisotropy in the chiral lattice. The magnetically ordered structure of Fe(pyrimidine)(2)Cl-2, however, is not chiral. The implications of these findings for the search of molecule based materials exhibiting chiral magnetic ordering are discussed.
Scientific journal, English - Supramolecular triangular and linear arrays of metal-radical solids using pyrazolato-silver(I) motifs
S Yamada; T Ishida; T Nogami
DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 2004, 6, 898-903, 2004, Peer-reviwed, New chelating radical ligands pzNNH, pzINH, and pzbisINH (3-pyrazolyl nitronyl nitroxide, 3-pyrazolyl imino nitroxide, and pyrazole-3,5-diyl bis(imino nitroxide), respectively) were prepared. Complexation of these ligands with Ag+ gave [Ag(pzNN)](n), [Ag(pzIN)](6), and [Ag(pzbisIN)](n), containing the corresponding anionic forms of the ligands. From the X-ray crystal structure analysis, [Ag(pzIN)](6) was characterized as a dimer of almost planar triangular moieties where the pyrazolate worked as a bridge, and metal-metal bonds brought about dimerization of triangles. [Ag(pzbisIN)](n) was characterized as a uniform zigzag chain consisting of pyrazolate bridges and Ag ions with a cis-N-pz-Ag-N-pz coordination structure. Antiferromagnetic interactions observed could be analyzed based on the structures determined for both compounds. Ferromagnetic coupling was observed in [Ag(pzNN)](n), and a polymeric structure was assumed although the crystal structure could not be determined. Novel supramolecular architectures using pyrazolate-substituted imino nitroxides have been developed, using the unique coordinative versatility of the pyrazolate derivatives.
Scientific journal, English - A self-assembled helix from 4,6-dimethylpyrimidine and copper(II) bromide
T Ishida; LM Yang; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 32, 11, 1018-1019, Nov. 2003, Peer-reviwed, A 1:1 polymeric complex of 4,6-dimethlpyrimidine and CuBr2 was spontaneously resolved to afford a 61 helix. Steric effects seem to play an important role for constructing a helical structure. Magnetic measurements showed a uniform S = 1/2 1-D behavior. A dinuclear complex is also obtained as a precursor to the polymeric complex.
Scientific journal, English - Molecular metamagnet [Ni(4lmNNH)(2)(NO3)(2)] (4lmNNH=4-lmidazolyl nitronyl nitroxide) and the related compounds showing supramolecular H-bonding interactions
C Aoki; T Ishida; T Nogami
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 42, 23, 7616-7625, Nov. 2003, Peer-reviwed, A new chelating radical ligand 41mNNH (2-(4-imidazolyl)-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide) was prepared, and complexation with divalent transition metal salts gave complexes, [M(41mNNH)(2)X-2], which showed intermolecular ferromagnetic interaction in high probability (7 out of 10 paramagnetic compounds investigated here). The nitrate complexes (X = NO3; M = Mn (1), Co (2), Ni (3), Cu (4)) crystallize isomorphously in monoclinic space group P2(1)/a. The equatorial positions are occupied with two 41mNNH chelates and the nitrate oxygen atoms are located at the axial positions. Magnetic measurements revealed that the intramolecular exchange couplings in 1, 2, and 4 were antiferromagnetic, while that in 3 was ferromagnetic with 2J/K-B = +85 K, where the spin Hamiltonian is defined as H = -2J(S-1.S-2 + S-2.S-3) based on the molecular structures determined as the linear radical-metal-radical triads. The intramolecular ferromagnetic interaction in 3 is interpreted in terms of orthogonality between the radical pi* and metal dsigma orbitals. Compounds 1-3 exhibited intermolecular ferromagnetic interaction ascribable to a two-dimensional hydrogen bond network parallel to the crystallographic ab plane. Complex 3 became an antiferromagnet below 3.4 K and exhibited a metamagnetic transition on applying a magnetic field of 5.5 kOe at 1.8 K The complexes prepared from metal halides, [M(41mNNH)(2)X-2] (X = Cl, Br; M = Mn, Co, Ni, Cu), showed intramolecular antiferromagnetic interactions, which are successfully analyzed based on the radical-metal-radical system. The crystal structures determined here on 1-4, [Mn(41mNNH)(2)Cl-2], and [Cu(41mNNH)(2)Br-2] always have intermolecular hydrogen bonds of H(imidazole)X-...(axial ligand)-M, where X = NO3, Cl, Br. This interaction seems to play an important role in molecular packing and presumably also in magnetic coupling.
Scientific journal, English - Rectangular tetragadolinium complex ion with a ground S=27/2 state containing bis(dimethylglyoximato)copper(II) as a ferrimagnetic exchange coupler
Y Kobayashi; S Ueki; T Ishida; T Nogami
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 378, 3-4, 337-342, Sep. 2003, Peer-reviwed, Pentanuclear [Cu(dmg)(2){Gd(hfac)(2)}(4)(AcO)(4)](Ph4P)(2) (1) (dmg = dimethylglyoximate dianion; hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) containing a central copper(II) and four peripheral gadolinium(III) ions was prepared and the crystal structure was determined by X-ray diffraction. Magnetic measurements on 1 revealed high ground spin multiplicity, as expected regardless of the sign of magnetic Cu...Gd coupling through N-O bridges. The ground state was suggested to be S-total = 27/2 with the exchange parameter 2J/k(B) = -2.9(2) K between the Gd and Cu ions. The antiferromagnetic coupling is operative owing to the largely distorted Gd-O-N-Cu bridges. (C) 2003 Elsevier B.V. All rights reserved.
Scientific journal, English - Ferro- and ferrimagnetic chains of hin-bridged copper(II) and manganese(II) and hnn-bridged manganese(II) complexes (hin=4,4,5,5-tetramethylimidazolin-1-oxyl; hnn=4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide)
T Ise; T Ishida; D Hashizume; F Iwasaki; T Nogami
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 42, 19, 6106-6113, Sep. 2003, Peer-reviwed, We have exploited potential utility of 4,4,5,5-tetramethylimidazolin-1-oxyl (hin) and 4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide (hnn) as mu-1,4 and mu-1,5 bridging ligands, respectively, carrying an unpaired electron in development of metal-radical hybrid magnets. X-ray diffraction measurements of [Cu(hfac)(2)hin] (1), [Mn(hfac)(2)hin] (2), and [Mn(hfaC)(2)hnn] (3) revealed one-dimensional metal-radical alternating chain structures, where hfac denotes 1,1,1,5,5,5-hexafluoropentane-2,4-dionate. Magnetic measurements of 1 indicate the presence of intrachain ferromagnetic coupling between copper and radical spins. The magnetic exchange parameter was estimated as 2J/k = 56.8 K based on an S = 1/2 equally spaced ferromagnetic chain model (H = -2JSigmaS(i).S(i+1)). This ferromagnetic interaction can be explained in terms of the axial coordination of the hin nitrogen or oxygen to Cull. The chi(m) T value of 2 and 3 increased on cooling, and the magnetic data could be analyzed by Seiden's ferrimagnetic chain model, giving 2J/k = -325 and -740 K, respectively. The antiferromagnetic interaction of 2 and 3 can be attributed to orbital overlap between the manganese and the oxygen or nitrogen magnetic orbitals. The exchange interactions between Cu-hin and Mn-hnn are larger than those of typical Cu- and Mn-nitronyl nitroxide complexes, indicating that the choice of small ligands is a promising strategy to bestow strong exchange interaction. Compound 3 became a ferrimagnet below 4.4 K, owing to ferromagnetic coupling among the ferrimagnetic chains.
Scientific journal, English - Metamagnetic behavior of [Ni(4ImNNH)(2)(NO3)(2)] having a ground high-spin state (4ImNNH=4-imidazolyl nitronyl nitroxide)
C Aoki; T Ishida; T Nogami
INORGANIC CHEMISTRY COMMUNICATIONS, ELSEVIER SCIENCE BV, 6, 8, 1122-1125, Aug. 2003, Peer-reviwed, A new chelating. radical ligand 4ImNNH (2-(4-imidazolyl)-4,4,5,5-tetramethylimidazolin-1-yloxyl-3-oxide) was prepared, and complexation with nickel(II) nitrate gave [Ni(4ImNNH)(2)(NO3)(2)] as a discrete mononuclear complex. Magnetic measurements revealed that [Ni(4ImNNH)(2)(NO3)(2)] had a ground high-spin state (S-total = 2) and exhibited metarnagnetic behavior below 3.4 K. (C) 2003 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Host-guest chemistry of radical-copper wheels. A supramolecular control of magnetic exchange coupling
T Ishida; J Omata; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 22, 14-17, 2133-2138, Jul. 2003, Peer-reviwed, The crystal of the hexanuclear wheel-shaped complex, [CuCl2.(4PMNN)](6) (1), has a channel structure in a direction perpendicular to the molecular plane (4PMNN = 4-pyrimidinyl nitronyl nitroxide). Excess LiCl, NaCl, or KCl added to a methanol solution of I yielded the corresponding guest-included compounds, (LiCl)(6)@1, (NaCl)(2)@1, and (KCl)(2)@1. The inclusion of the guests was confirmed by means of elemental analysis and X-ray diffraction study. The crystallographic c length and the cell volume were slightly shrunk by the guest inclusion. The ferromagnetic interaction, which is ascribed to intermolecular contacts between the nitronyl nitroxide groups, was remarkably enhanced almost in proportion to the cell shrinkage. Similar enhancement was observed for the host-guest complexes from the bromide analogue [CuBr2.(4PMNN)](6)]. The crystallization in the presence of water gave (H2O)(n)@1. In addition to enhancement of the ferromagnetic interaction of (H2O)(n)@1, we found that the ferromagnetic interaction decreased back to a level of that of the empty 1 after removal of H2O by evacuation. (C) 2003 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - meta-phenylene-bridged bis(imino nitroxide) biradicals as potential high-spin ligands
T Ichimura; K Doi; C Mitsuhashi; T Ishida; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 22, 14-17, 2557-2564, Jul. 2003, Peer-reviwed, Frozen-solution ESR spectra of 4-hydroxy-1,3-phenylenebis(imino nitroxide) (1) and 2-hydroxy-5-methyl-1,3-phenylenebis(imino nitroxide) (2) in toluene showed fine structures due to the triplet states (imino nitroxide stands for 2-substituted 4,4,5,5-tetramethylimidazolin-3-yloxyl). The temperature dependence of the Deltam(s) = +/- 2 signal intensity for I followed the Curie law, suggesting that I has a ground triplet state. On the other hand, the triplet signal intensity of 2 did not obey the Curie law. The intramolecular magnetic coupling seems to depend on the twist angle between the imino nitroxide group and benzene ring. Complexation with Cu(CH3CO2)(2) . H2O in ethanol gave a mononuclear complex, Cu(L-1)(2), where L-1 is the anionic form derived from 1. The X-ray diffraction study of Cu(L-1)(2) revealed that the central copper(II) ion had a twisted square plane; the dihedral angle between two chelating O-Cu-N planes was 45degrees. The magnetic measurements of Cu(L-1)(2) indicated the presence of intramolecular ferromagnetic interaction, which is ascribed mainly to a ground quartet formation at the directly bonded radical-copper-radical moiety with J(radical-copper)/k(B) = +132 +/- 5 K, where the Heisenberg spin Hamiltonian is defined as H = -2JS(i)S(j). (C) 2003 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Nitronyl nitroxide substituted aniline o-APNN with a three-dimensional hydrogen bond network showing ferromagnetic interaction
K Doi; T Ishida; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 32, 6, 544-545, Jun. 2003, Peer-reviwed, o-Aminophenyl nitronyl nitroxide (o-APNN) was prepared as the first aniline-substituted nitronyl nitroxide. X-Ray crystallographic analysis reveals a 3-D hydrogen bonded network due to the branching nature of -NH2. Magnetic measurements indicate the presence of ferromagnetic interaction.
Scientific journal, English - Effect of staggered field in S = 1/2 antiferromagnetic chain: copper pyrimidine
T Asano; D Nomura; Y Inagaki; Y Ajiro; H Nojiri; Y Narumi; K Kindo; T Ishida; T Nogami
PHYSICA B-CONDENSED MATTER, ELSEVIER SCIENCE BV, 329, 1006-1007, May 2003, Peer-reviwed, We report electron spin resonance (ESR) and magnetization measurements of the S = 1 2 antiferromagnetic Heisenberg chain, Cu pyrimidine, [PM . Cu(NO3)(2) . (H2O)(2)](n) (PM = pyrimidine). The effect of staggered fields due to both the alternating g-tensor and the Dzyaloshinskii-Moriya interaction is clearly observed for the ESR line width and magnetization. (C) 2003 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Hydroiminonitroxide complexes with metal hexafluoroacetylacetonates
T Ise; T Ishida; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 137, 1-3, 1281-1282, Apr. 2003, Peer-reviwed, Hybrid metal-radical magnetic solids, Cu(bfac)(2) . HIN (1) and Mn(hfac)(2) . HIN (2) were synthesized, where HIN denotes 4,4,5,5tetramethylimidazolin-1-oxyl. X-ray diffraction measurements of 1 and 2 showed 1-dimensional metal-radical alternating chain structures. Magnetic data of 1 and 2 could be analyzed by 1-D ferro- and ferrimagnetic chain models, respectively.
Scientific journal, English - Magnetic properties of 9,9-disubstituted 9,10-dihydroacridine-10-yloxyls
M Seino; Y Akui; T Ishida; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 133, 581-583, Mar. 2003, Peer-reviwed, Ferromagnetic intermolecular interactions were observed for 9-R-9-(pentadeuteriophenyl)-9,10-dihydroacridine-10-yloxyls (R = n-C12H25, n-C13H24. Superexchange-like interaction across the 9-phenyl ring is proposed, as illustrated by acridinoxyl parallel to phenyl perpendicular to acridinoxyl, where the symbols parallel to and perpendicular to denote the presence and absence of orbital overlaps, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Hybrid magnetic solids of radical-substituted heteroaromatic compounds with metal halides
T Matsuyama; Y Iwata; T Ishida; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 133, 611-613, Mar. 2003, Peer-reviwed, Complexes of manganese(II), cobalt(II), nickel(II), and copper(II) chlorides with 5-pyrimidinyl nitronyl nitroxide (5PMNN) and pyrazinyl nitronyl nitroxide (PZNN) were synthesized. Ni- and CoCl2.(5PMNN)(2) showed magnetic phase transitions at 5.8 and 2.3 K, respectively, and spin-flip behavior below the transition temperatures. X-ray crystal structure analyses revealed that Mn- and CoCl2.(PZNN)(2) were mononuclear. (C) 2002 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Low temperature deuterium NMR studies on magnetism of TEMPO derivatives
G Maruta; S Takeda; M Ooishi; R Imachi; T Ishida; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 133, 577-579, Mar. 2003, Peer-reviwed, We measured deuterium NMR of three TEMPO (2,2,6,6-tetramethylpiperidin-1-yloxyl) derivatives, 4-hydroxy-d(1)-TEMPO, 4-hydroxyimino-d(1)-TEMPO and Cl-C6D4-CD=N-TEMPO down to 2 K to investigate the magnetic local structure around the selectively deuterated sites. Hyperfine coupling constants (HFCCs) determined from the spectra are in good agreement with the results of our previous experiments at higher temperatures. We found: (i) each deuterium, which forms a hydrogen bond with the nitroxide group in the crystalline phases of 4-hydroxy- and 4-hydroxyimino-TEMPO has a large negative BFCC; (ii) electron spin density on Cl-C6D4-group in Cl-C6D4-CD=N-TEMPO crystal remains small in magnitude at 4.2 K. (C) 2002 Published by Elsevier Science B.V.
Scientific journal, English - Metal-azide-pyrimidine complexes M(N-3)(2)(pm) with a three-dimensional network showing weak ferromagnetism for M = Mn and Fe and antiferromagnetism for M = Co and Ni
Y Doi; T Ishida; T Nogami
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 75, 11, 2455-2461, Nov. 2002, Peer-reviwed, Antiferromagnetic phase transitions of M(N-3)(2)(pm) were observed at 51, 39,41, and 46 K for M = Mn, Fe, Co, and Ni, respectively; here pm denotes pyrimidine. Single-crystal X-ray crystallographic analysis for M = Mn, Fe, and Co and powder X-ray diffraction measurements for M = Ni revealed that they were isomorphous. The N-3 and pm moieties contribute mu-1,3-bridged two-dimensional and mu-1,3-bridged one-dimensional structures, respectively, thus forming a three-dimensional framework. Antiferromagnetic couplings through the bridging ligands are consistent with superexchange mechanisms based on the coordination geometry determined. Small spin canting was observed below the transition temperature for M = Mn and Fe. The cant angles are estimated to be 0.06 and 0.13degrees, respectively, from the spontaneous magnetization at 10 K.
Scientific journal, English - Crystal structures and magnetic properties of copper(II) hexafluoroacetylacetonate complexes with hnn and hin and manganese(II) hexafluoroacetylacetonate complex with hin (hnn=4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide; hin=4,4,5,5-tetramethylimidazolin-1-oxyl)
T Ise; T Ishida; T Nogami
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 75, 11, 2463-2468, Nov. 2002, Peer-reviwed, We report here the structures and magnetic properties of hnn and hin complexes with copper(H) and manganese(II) hexafluoroacetylacetonates, [{Cu(hfac)(2)(H2O)}(2)(mu-hnn)] (1), [Cu(hfac)(2)(hin)(2)] (2), and [Mn(hfac)2(hin)2] (3). X-ray crystallographic analysis of 1 revealed that 1 was a dinuclear complex containing an lum bridge. Magnetic measurements of 1 indicate the presence of intramolecular ferromagnetic coupling between copper and radical spins. The data were analyzed as a metal-radical-metal three-spin system, giving 2J/k = + 16.2 K (H = -2J(S1S2 + S2S3)). The ferromagnetic interaction can be explained in terms of the axial coordination of the hnn nitrogen to Cu(11). Complexes 2 and 3 were revealed to be isomorphous mononuclear complexes possessing two hin ligands. Although the molecules have a radical-metal-radical system, the magnetic data of 3 could not be analysed only with intramolecular interactions. Strong intermolecular antiferromagnetic interactions (2lJl/k much greater than 300 K) were suggested among the hin ligands because the inter-atomic (ON)-N-... distances (2.41-2.51 Angstrom) were shorter than the sum of the van der Waals radii for 2 and 3. These strong interactions are successfully introduced to metal-radical hybrid systems owing to the choice of small. ligands, although the complexes do not possess polymeric networks.
Scientific journal, English - Convenient synthesis and host-guest compounds of 9,9 '(10H,10 ' H)-spirobiacridines
M Ooishi; M Seino; R Imachi; T Ishida; T Nogami
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 43, 32, 5521-5524, Aug. 2002, Peer-reviwed, 9,9'(10H, 10'H)-Spirobiacridine and its 2-methoxy derivative were prepared from the corresponding diphenylamines and acridone in three steps. A nearly D-2d molecular skeleton of the spiro compounds was confirmed by X-ray crystallographic analysis. The spirobiacridines can work as a new class of host compounds owing to their ability to form nearly rectangular hydrophobic cages in the crystal. (C) 2002 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Low-temperature heat capacity and one-dimensional ferromagnetic behavior of the organic free radical 4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (BATMP)
T Sakakibara; Y Miyazaki; T Ishida; T Nogami; M Sorai
JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 106, 25, 6390-6394, Jun. 2002, Peer-reviwed, Heat capacities of the organic free radical ferromagnet 4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (BATMP) crystal were measured in the temperature range between 0.1 and 300 K by adiabatic calorimetry. A ferromagnetic phase transition was found at T-C = 0.19 K, and a broad heat-capacity anomaly was found arising from the short-range ordering above T-C characteristic of low-dimensional magnetic spin systems. The enthalpy and entropy gains due to both the magnetic phase transition and the heat-capacity anomaly were evaluated to be DeltaH = 3.86 J mol(-1) and DeltaS = 5.64 J K-1 mol(-1), respectively. The value of the experimental magnetic entropy agrees well with the theoretical value R ln 2 (5.76 J K-1 mol(-1)) expected for a spin quantum number S = 1/2 spin system (R is the gas constant). The magnetic heat capacity hump due to the short-range order was well accounted for in terms of an S = 1/2 one-dimensional ferromagnetic Heisenberg model with the intrachain exchange interaction J/k(B) = 0.95 K (k(B) is Boltzmann's constant). This fact suggests that BATMP crystal is a one-dimensional ferromagnet above T-C. The spin wave analysis of the magnetic heat capacities below T-C revealed that BATMP crystal is in a three-dimensional ferromagnetic state below T-C and the averaged interchain exchange interaction is J'/k(B) = 0.026 K.
Scientific journal, English - Novel organic-inorganic molecular assembly: a copper(I) and copper(II) mixed-valent cluster with bromide bridges and paramagnetic ligands
T Katayama; T Ishida; T Nogami
INORGANICA CHIMICA ACTA, ELSEVIER SCIENCE SA, 329, 31-35, Feb. 2002, Peer-reviwed, Complex pbt(2)Cu(8)Br(12) [pbt = pyridine-2,6-diylbis(methyleneamino-TEMPO)] was synthesized from CuBr2 and a new ligand pbt, and characterized by means of X-ray crystal structure analysis and magnetic measurements. The centrosymmetric molecule consists of a Cu6Br10 cluster sandwiched with two pbt.CuBr complexes. Detailed geometrical analysis and magnetic analysis reveal the presence of four copper(I) and four copper(II) ions in a molecule. Antiferromagnetic couplings observed can be attributed to the intermolecular radical...radical and intramolecular copper(II)...copper(II) interactions. (C) 2001 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Radical-copper macrocycles and related compounds
J Omata; T Ishida; D Hashizume; F Iwasaki; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 376, 455-462, 2002, Peer-reviwed, 4-Pyrimidinyl nitronyl nitroxide (4PMNN) was synthesized and characterized, and four 4PMNN-metal(II) chloride complexes were investigated. Hexanuclear macrocyclic [CUCl2.(4PMNN)](6) shows intermolecular ferromagnetic interaction. MnCl2.(4PMNN) exhibits antiferromagnetic interaction. Mononuclear COCl2.(4PMNN)2 shows ferrimagnetic phase transition at ca. 3 K. NiCl2.(4PMNN)(2) are practically diamagnetic below 100 K.
Scientific journal, English - Magnetic phase transition of FEII, COII and NIII complexes bridged by pyrimidine and dicyanamide
T Kusaka; T Ishida; D Hashizume; F Iwasaki; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 376, 463-468, 2002, Peer-reviwed, X-Ray diffraction study reveals that complexes M-II[N(CN)(2)](2)(pyrimidine) (M = Fe, Co, Ni) have an isomorphous 3-D network, in which N(CN)(2)(-) and pyrimidine contribute mu-1,5-bridged 2-D and mu-1,3-bridged 1-D structures, respectively. Magnetic measurements indicate that the Fe, Co, and Ni complexes behave as weak ferromagnets below the transition temperatures of 3.2, 1.8, and 8.3 K, respectively.
Scientific journal, English - Solvated magnets of Fe[N(CN)(2)](2)(pyrimidine): Transition phenomena tuned by guests
T Kusaka; T Ishida; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 379, 259-264, 2002, Peer-reviwed, Low-temperature magnets derived from Fe[N(CN)(2)](2)(pyrimidine) have guest molecules incorporated in the clearance of the 3-D framework. The ac and dc magnetic susceptibility measurements reveal that the temperature of magnetic phase transition (T-N) depends on the guest molecules. They are characterized as weak ferromagnets below T-N. The compound containing uncoordinated pyrimidine molecules as a guest showed the highest T-N of 5.6 K in this family.
Scientific journal, English - First isolation and characterization of an HIN complex, CdCl2(HIN)(4) (HIN=4,4,5,5-tetramethylimidazolin-1-oxyl)
T Ise; T Ishida; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 379, 147-152, 2002, Peer-reviwed, We report here for the first time the X-ray crystal structure and magnetic properties of an HIN complex, CdCl2(HIN)(4), showing very strong antiferromagnetic interaction. X-ray crystal structure analysis reveals that intermolecular O...N distance (2.33 and 2.42 Angstrom) are considerably short.
Scientific journal, English - Antiferromagnetic coupling of transition metal spins across pyrimidine and pyrazine bridges in dinuclear manganese(II), cobalt(II), nickel(II) and copper(II) 1,1,1,5,5,5-hexauoropentane-2,4-dionate complexes
T Ishida; T Kawakami; S Mitsubori; T Nogami; K Yamaguchi; H Iwamura
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 2002, 16, 3177-3186, 2002, Peer-reviwed, Dinuclear manganese(), cobalt(), nickel(), and copper() complexes bridged by pyrimidine and pyrazine derivatives, L[M(hfac)(2)](2) [L = 4,6-di(2-pyridyl) pyrimidine (DPPM), 2,3-di(2-pyridyl) pyrazine (DPPZ); M = Mn, Co, Ni, Cu; hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate], were synthesized and their magnetic properties were studied. Antiferromagnetic couplings across the pyrimidine ring were observed for the DPPM complexes with the exchange parameters, 2J/k(B), of -0.40, -3.1, -9.1 and -46 K for M = Mn, Co, Ni and Cu, respectively. The pyrimidine nitrogen atoms are coordinated at the axial position of each metal ion for M = Mn, Co and Ni, and coordinated equatorially for M = Cu. The DPPZ complexes also exhibited antiferromagnetic interactions, which are weaker than those of the DPPM complexes. Crystal structure analysis indicated that the molecular structures of the four DPPZ complexes are essentially the same in spite of various space groups. Ab initio unrestricted Hartree-Fock calculations on DPPM[Cu(hfac)(2)](2) predicting a positive effective exchange integral (J) are inconsistent with the experiments, because of overestimation of the role of pi-type spin-polarization in DPPM. The J value from the density functional UB3LYP calculations is close to the experimentally determined value, which arises from a sigma-type exchange pathway across the pyrimidine ring.
Scientific journal, English - Ferromagnetic exchange coupling of vanadium(IV) d pi spins across pyrimidine rings: Dinuclear complexes of oxovanadium(IV) bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionate) bridged by pyrimidine derivatives
T Ishida; S Mitsubori; T Nogami; N Takeda; M Ishikawa; H Iwamura
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 40, 27, 7059-7064, Dec. 2001, Peer-reviwed, Dinuclear oxovanadium(IV) complexes bridged by pyrimidine derivatives, L[VO(hfac)(2)](2) [L = pyrimidine (PM), 4-methylpyrimidine (MPM), 4,6-dimethylpyrimidine, 4-aminopyrimidine, and quinazoline; hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate], were synthesized and characterized. All of them showed intramolecular ferromagnetic interaction, and the magnetic susceptibilities were analyzed on the basis of the singlet-triplet model, giving 2J/k(B) = 2.2-5.5 K. PM[VO(hfac)(2)](2) crystallized in a monoclinic space group C2/c with a = 34.092(2), b = 6.9783(4), and e = 16.4940(9) Angstrom, beta = 109.104(1)degrees, V = 3707.8(4) Angstrom (3), and Z = 4 for C24H8F24N2O10V2, and MPM[VO(hfac)(2)](2) gave isomorphous crystals. A semiempirical calculation study based on the determined structure suggests the presence of d pi -p pi interaction between vanadium and pyrimidine nitrogen atoms. Ferromagnetic coupling is explained in terms of a spin-polarization mechanism across the pyrimidine bridge. The intermolecular ferromagnetic interaction of PM[VO(hfac)(2)](2) call be interpreted by the contact between the spin-polarized pyrimidine moiety and the oxovanadium oxygen atom in an adjacent molecule.
Scientific journal, English - Bis(hfac)-copper(II) complexes bridged by pyrimidines showing magnetic interactions
M Yasui; Y Ishikawa; T Ishida; T Nogami; F Iwasaki
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, MUNKSGAARD INT PUBL LTD, 57, 772-779, Dec. 2001, Peer-reviwed, Crystals of bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis-pyrimidinecopper(II) (1), bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis(4-methylpyrimidine)copper(II) (2), bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis(quinazoline)- copper(II) (3) showed ferromagnetic interactions at extremely low temperature. Crystal structure analyses revealed that these complexes were catena-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)[mu -pyrimidine-N-1 :N-3]copper(II), [Cu(hfac)(2)-(pm)(2)](n), catena-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)[mu -4-methylpyrimidine-N-1:N-3]copper(II), [Cu(hfac)(2)(4-Me-pm)](n), and catena-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)[mu -pyrimidine-N-1 :N-3]copper(II), [Cu(hfac)(2)-(qz)](n), for (1), (2) and (3), respectively. In (1) and (2) the pyrimidines bridge the Cu atoms with an axial-equatorial mode to form one-dimensional spiral chains. Complex (3) also forms a one-dimensional chain structure. The coordination mode of (3) is axial-axial at room temperature, while axial-equatorial at 120 K. On the other hand, the structure of the other modification of the 4-methylpyrimidine complex (4), showing paramagnetic properties, was revealed to be a trinuclei complex bridged by two 4-methylpyrimidines, tris[bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)copper(II)][bis-mu -4-methyl-pyrimidine-N-1:N-3]. The chain structures with an axial-equatorial coordination mode of the bridging organic moieties should play an important role in the appearance of the ferromagnetic interactions.
Scientific journal, English - Radical-copper wheels: Structure and magnetism of hexanuclear hybrid arrays
J Omata; T Ishida; D Hashizume; F Iwasaki; T Nogami
INORGANIC CHEMISTRY, AMER CHEMICAL SOC, 40, 16, 3954-3958, Jul. 2001, Peer-reviwed, Complexation of copper(II) bromide and chloride with 4-pyrimidinyl nitronyl nitroxide (4PMNN) as a bridging ligand gave discrete hexanuclear complexes carrying 12 spins, [CuX2. (4PMNN)](6) [X = Br (1), Cl (2)], which crystallize in a trigonal space group R-3(-). The crystallographic parameters are C11H15Br2CuN4O2.0.3H(2)O, a = 28.172(2), c = 12.590(2) Angstrom, V = 8653(2) Angstrom (3), and Z = 18 for 1, and C11H15Cl2CuN4O2.0.3H(2)O, a = 28.261(2), c = 12.378(1) Angstrom, and Z = 18 for 2. The hexanuclear arrays construct a perfect column perpendicular to the molecular plane. The diameter of the resultant honeycomblike channel is ca. 11.5 Angstrom defined by the interatomic distance of two opposing copper ions. Their magnetic behavior is interpreted as the simultaneous presence of ferro and antiferromagnetic couplings. The ferromagnetic couplings are attributed to the interactions between a copper spin and the axially coordinated nitronyl nitroxide spin and between nitronyl nitroxide groups through van der Waals contacts. The antiferromagnetic coupling is due to the interaction between copper ions across the pyrimidine bridges.
Scientific journal, English - Dipyrimidine-copper(II) dinitrate complexes showing magnetic interactions
M Yasui; Y Ishikawa; N Akiyama; T Ishida; T Nogami; F Iwasaki
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, MUNKSGAARD INT PUBL LTD, 57, 288-295, Jun. 2001, Peer-reviwed, Crystals of Cu-II (NO3)(2)(pm)(3) (1), and two crystalline forms of Cu-II(NO3)(2)(H2O)(2)(pm)(2), (2) and (3), showed ferromagnetic, antiferromagnetic and paramagnetic interactions at extremely low temperatures, respectively. Crystal structure analyses revealed that the complexes were catena-dinitrato[mu -pyrimidine-kappaN(1):kappaN(3)]-(pyrimidine-N-1)copper(II), [Cu(NO3)(2)(pm)(2)](n), catena-diaquadinitrato[mu -pyrimidine-kappaN(1) :kappaN(3)]copper(II), [Cu(NO3)(2)(H2O)(2)(pm)](n), and diaquadinitratodipyrimidine-copper(II), Cu(NO3)(2)(H2O)(2)(pm)(2) for (1), (2) and (3), respectively. In (1) the Cu atom is coordinated by the two nitrates and N atoms of the non-bridging pyrimidine and bridging pyrimidine to form a one-dimensional coordination polymer. The complex is a five-coordinated square pyramid and can be regarded as a pseudo-seven-coordinated complex, since other short non-bonding Cu . . .O contacts are observed. In the crystals of (2) the pyrimidine bridges the Cu atoms to form a one-dimensional coordination chain. On the other hand, complex (3) is not a coordination polymer. It is important to form a coordination polymer for the appearance of the magnetic interactions. Types of coordination of the bridging organic moieties should also play an important role in magnetic properties. Magnetic measurements of (1) and (2) show that they are good examples of uniform S = 1/2 ferro- and antiferromagnetic Heisenberg chains with exchange parameters 2J/kB = +1.8 and -36 K, respectively.
Scientific journal, English - Radical-copper hexanuclear arrays showing intermolecular ferromagnetic interactions
J Omata; T Ishida; D Hashizume; F Iwasaki; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 20, 11-14, 1557-1561, May 2001, Peer-reviwed, Hexanuclear arrays [CuX2. (4PMNN)](6) (X = Br, Cl; 4PMNN = 4-pyrimidinyl nitronyl nitroxide) construct a perfect column perpendicular to the molecular plane and consequently a honeycomb-like channel structure is formed. The diameters of the channels are approximately 11.5 Angstrom. The inner axial sites of the copper ions remain vacant and are thought to br: available for further coordination. The host-guest complexes using [CuCl2. (4PMNN)](6) were synthesized, and their ferromagnetic interactions enhanced by the guest inclusion. A possible supramolecular control of molecular magnetism is proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Ferromagnetic S=1 chain formed by a square Ni2S2 motif in Ni(qt)(2) (qt = quinoline-8-thiolate). Magnetic properties of related compounds
T Miyake; T Ishida; D Hashizume; F Iwasaki; T Nogami
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 20, 11-14, 1551-1555, May 2001, Peer-reviwed, ML, complexes [M = Fe2+, Co2+, Ni2+, Cu2+; L = quinolin-8-olale (q), quinoline-8-thiolate (qt)] were prepared and their magnetic properties were studied. X-ray crystal structure analysis of Ni(qr), reveals that nickel(II) ions are arranged to form a one-dimensional structure with double thiolate bridges. Magnetic susceptibility measurements of Ni(qt), indicate that the nickel S= 1 spins are ferromagnetically coupled within a chain. Other ML, showed antiferromagnetic interactions. Magnetic properties of molecular complexes of ML, with 7,7,8,8-tetracynanoquinodimethane (TCNQ) were also investigated. The crystal structure of Ni(qt)(2)(TCNQ) was determined. (C) 2001 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Zero-field muon spin rotation study on TEMPO-based magnets, Ar-CH = N-TEMPO
T Ishida; S Ohira; Watanabe, I; T Nogami; K Nagamine
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 20, 11-14, 1545-1549, May 2001, Peer-reviwed, Long-range magnetic orderings are demonstrated by zero-field muon spin rotation/relaxation measurements on the genuine organic Free radical crystals, 4-(p-chlorobenzylideneamino)-, 4-(p-phenylbenzylideneamino)-, and 4-(benzylideneamino)-TEMPOs (TEMPO = 2,7,6,6-tetramethylpiperidin-1-yloxyl) with T-C values of 0.28, 0.22, and 0.17 K, respectively, and 4-(4-pyridylmethyleneamino)-TEMPO with T-N of approximate to0.07 K. From comparison between the crystal structures and internal fields at the muon sites, dominant two-dimensional ferromagnetic interaction is confirmed and inter-sheet dipolar interaction is proposed for bulk magnetism. (C) 2001 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Anomalous magnetism in organic radical ferromagnets 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyl just above T-C studied by the mu SR method
S Ohira; K Nakayama; T Ise; T Ishida; T Nogami; Watanabe, I; K Nagamine
POLYHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 20, 11-14, 1223-1227, May 2001, Peer-reviwed, The magnetic property of 4-arylmethyleneamino-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yloxyl) just above the Curie temperature was studied by muon spin relaxation (mu SR) method microscopically. In the longitudinal-field (LF) measurement, muon spin depolarization due to dynamical radical spin fluctuations was expected. However, we observed a random static internal magnetic field at the muon site down to T-C. A distribution width of the random internal magnetic field increased, as if induced by LF, with increasing LF, and was saturated eventually. This remarkable behavior appears below the temperature where the ac susceptibility starts to increase rapidly [Chem. Lett. (1995) 635; Chem. Lett. (1994) 919; Chem. Lett. (1994) 29].
We report the critical phenomena observed in the mu SR studies on the TEMPO derivatives and discuss the relationship between the results and the magnetic structure in the ordered state. (C) 2001 Elsevier Science Ltd. All rights reserved.
Scientific journal, English - Synthesis and properties of new oxygen-containing fulvalene derivatives: dibenzo- and dinaphthotetraoxafulvalenes and dibenzodioxadithiafulvalene
T Nogami; K Tanaka; T Ishida; A Kobayashi
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 120, 1-3, 755-756, Mar. 2001, Peer-reviwed, Novel oxygen-containing fulvalene-derivatives, DBTOF, DNTOF, and DBOTF, were synthesized as donor molecules for highly conducting organic complexes. Cis- and trans-forms of DBOTF could be separated, and their molecular and crystal structures were determined by X-ray crystallography. From cyclic voltammetries and molecular orbital calculations of these donor molecules, the order of donor abilities of DBTXF series and DBOTF were established. Trans-DBOTF-TCNQ complex was an insulator.
Scientific journal, English - Single-component organic semiconductors based on novel radicals that exhibit electrochemical amphotericity: Preparation, crystal structures, and solid-state properties of N,N '-dicyanopyrazinonaphthoquinodiiminides substituted with an N-alkylpyridinium unit
T Suzuki; S Miyanari; Y Tsubata; T Fukushima; T Miyashi; Y Yamashita; K Imaeda; T Ishida; T Nogami
JOURNAL OF ORGANIC CHEMISTRY, AMER CHEMICAL SOC, 66, 1, 216-224, Jan. 2001, Peer-reviwed, N,N'-Dicyanonaphthoquinodiimines fused with a pyrazine ring 1 were prepared from the corresponding quinones 4. The new accepters 1 have a planar pi -system and undergo reversible two-stage 1e-reduction. Quaternization of the pyridyl substituent in 1d-f gave pyridinium derivatives 2d(+), 2e(+), and R-3(+), respectively, which are stronger accepters that undergo three-stage le-reduction. Upon electrochemical. reduction of these cations, novel radicals 2d(.) 2e(.), and R-3(.) were generated and isolated as stable solids. The molecular geometries determined by X-ray analysis indicated that these radicals adopt a zwitterionic structure, in which the unpaired electron is located on the quinodiimine unit but not on the pyridyl group. These novel radicals undergo facile and reversible 1e-oxidation as well as two-stage le-reduction. The observed amphotericity endows the radicals with electrical conductivities (10(-5) to 10(-9) S cm(-1)), and these thus represent a new motif for single-component organic semiconductors.
Scientific journal, English - Pressure effects of genuine organic crystalline ferromagnet possessing intermolecular contacts between nitroxide oxygen and methyl hydrogen atoms
M Mito; T Kawae; M Hitaka; K Takeda; T Ishida; T Nogami
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 333, 1-2, 69-75, Jan. 2001, Peer-reviwed, We have found the pressure-induced (1) periodical down-up variation of transition temperature (T-c), (2) ferro- to antiferro-magnetic transition and (3) reduction of the magnetic lattice dimensionality in a genuine organic crystalline bulk-ferromagnet p-Cl-C6H4-CH=N-TEMPO (T-c = 0.28 K) with spin polarizations on intermolecular contacts between the nitroxide oxygen and methyl hydrogen atoms (C-H . . .O-N contacts). These phenomena can be understood by the pressure-induced rotation of the methyl moiety relevant to the interaction-mechanism through C-H . . .O-N contacts. (C) 2001 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Zero-field muon spin rotation study on genuine organic ferromagnets, 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls (aryl=4-biphenylyl and phenyl)
T Ishida; S Ohira; T Ise; K Nakayama; Watanabe, I; T Nogami; K Nagamine
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 330, 1-2, 110-117, Nov. 2000, Peer-reviwed, Long-range magnetic orderings are unequivocally demonstrated by zero-field muon spin rotation/relaxation measurements on the genuine organic free radical crystals of 4-(p-phenylbenzylideneamino)- and 4-(benzylideneamino)-TEMPOs (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yloxyl). The T-C's are 0.22 and 0.17 K and the critical exponents (beta 's) 0.356 and 0.362, respectively. Dominant two-dimensional ferromagnetic interaction is confirmed and inter-sheet dipolar interaction is proposed for bulk ferromagnetism. (C) 2000 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Low-temperature magnets M[N(CN)(2)](2)(pyrimidine) (M = Fe and Co) with a 3-D network
T Kusaka; T Ishida; D Hashizume; F Iwasaki; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 10, 1146-1147, Oct. 2000, Peer-reviwed, X-Ray crystal structure analyses reveal that the title complexes have a 3-D network, in which N(CN)(2)(-) and pyrimidine contribute mu -1,5-bridged 2-D and mu -1,3-bridged 1-D structures, respectively. Magnetic measurements indicate that the Fe and Co complexes have spontaneous magnetizations below the transition temperatures of 3.2 and 1.8 K, respectively.
Scientific journal, English - Magnetic-field induced gap and staggered susceptibility in the S=1/2 chain [PM center dot Cu(NO3)(2)center dot(H2O)(2)](n) (PM = pyrimidine)
R Feyerherm; S Abens; D Gunther; T Ishida; M Meissner; M Meschke; T Nogami; M Steiner
JOURNAL OF PHYSICS-CONDENSED MATTER, IOP PUBLISHING LTD, 12, 39, 8495-8509, Oct. 2000, Peer-reviwed, Single-crystal magnetic susceptibility and specific heat studies of the one-dimensional copper complex [PM . Cu(NO3)(2)bullet>(*) over bar * (H2O)(2)](n) (PM = pyrimidine) show that it behaves Like a uniform S = 1/2 antiferromagnetic Heisenberg chain, characterized by the exchange parameter J/k(B) = 36 K. Specific heat measurements in the applied magnetic field, however, reveal the formation of a field-induced spin excitation gap, whose magnitude depends on the magnitude and direction of the field. This behaviour is inconsistent with the ideal S = 1/2 Heisenberg chain. In the low-temperature region, a contribution to the susceptibility, approximately proportional to 1/T, is observed which varies strongly with the varying direction of the magnetic field. The field-induced gap and the 1/T contribution are largest for the same field direction. Previous observations of a field-induced gap in the related compounds copper benzoate and Yb4As3 have been explained by the alternating g tensor and alternating Dzyaloshinkii-Moriya interaction, producing an effective staggered magnetic field at the Cu and Yb ions. We apply this model to [PM . Cu(NO3)(2)bullet>(*) over bar * (H2O)(2)](n) and obtain a consistent quantitative explanation of the low-temperature susceptibility, the field-induced gap and their dependence on the magnetic-field direction.
Scientific journal, English - One-dimensional S = 1 ferromagnetic chain formed by a square Ni2S2 motif in Ni(qt)(2) (qt = quinoline-8-thiolate)
T Miyake; T Ishida; D Hashizume; F Iwasaki; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 8, 952-953, Aug. 2000, Peer-reviwed, X-ray crystallographic analysis of the title complex reveals that nickel(II) ions are arranged to form a one-dimensional chain structure with double thiolate-bridges. The Ni-S-Ni angle is 94.3 degrees. Magnetic susceptibility measurements indicate that the nickel S = 1 spins are ferromagnetically coupled within a chain.
Scientific journal, English - mu SR studies on the organic radical magnet, 4-arylmethyleneamino-TEMPO
S Ohira; T Ishida; T Nogami; Watanabe, I; FL Pratt; K Nagamine
PHYSICA B, ELSEVIER SCIENCE BV, 289, 123-127, Aug. 2000, Peer-reviwed, Muon spin rotation measurement under a transverse field (TF-mu SR) and muon spin relaxation under a longitudinal field (LF-mu SR) were carried out on two organic radical ferromagnets, 4-(p-chlorobenzylideneamino)-TEMPO and 4-(p-phenylbenzglideamino)-TEMPO just above T-C, in order to understand critical phenomena and muon states in these systems, A muon spin rotation Frequency which increased as temperature was lowered down to 0.3 K was observed under TF. In the LF-mu SR, a muonium decoupling was observed. A muon spin resonance study on 4-(p-chlorobenzylidencamino)-TEMPO was carried out above T-C. The hyperfine field at the muon site was found to be about 115 G/mu(B) from the K-chi plot. We discuss the origin of the large shift observed under TF and the relationship between the TF-mu SR and RF resonance results. (C) 2000 Elsevier Science B.V. All rights reserved.
Scientific journal, English - The experimental deformation electron-density distributions of 4-arylmethyleneamino-2,2,6,-tetramethyl-1-piperidyloxyl (TEMPO) radicals: Relations between electron densities and intermolecular interactions
M Yasui; E Kan-nari; T Ishida; T Nogami; F Iwasaki
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 73, 6, 1333-1340, Jun. 2000, Peer-reviwed, Some of the 4-arylmethyleneamino-TEMPO radicals (TEMPO = 2,2,6,6-tetramethyl-1-piperidyloxyl), such as 4-(4-chlorobenzylideneamino)TEMPO (1) and 4- (benzylideneamino)TEMPO (2), showed intermolecular ferromagnetic interactions at an extremely low temperature. The experimental electron-density distributions of these compounds were investigated by the X-ray diffraction method. Intensity data were measured at 100 K up to 2 theta(max)(Mo K alpha) = 120 degrees and 95 degrees for 1 and 2, respectively. Deformation electron-density distributions were calculated from the structure factors after the refinements by the multipole expansion method. These electron-density distributions suggested that the unpaired electron of the O radical atom was not located on the O atom, but was rather located in the pi*-orbital of the N-O bond. Lone-pair densities of the radical O atom are located in the >N-O plane showing the sp(2) hybridization. From the crystal structures, it has been proposed that the ferromagnetic interactions are transferred through CH ... O interactions between radical O atoms and beta-H atoms of the neighboring TEMPO rings. The beta-H atoms of the neighboring TEMPO rings contact with the O atom in the direction toward the pi*-orbital of the N-O bond, not in the direction of the lone-pair densities of the O atom. The present studies support the mechanism of the intermolecular ferromagnetic interactions through the beta-H atoms. Studies of electron densities from the view point of the intermolecular interactions are important.
Scientific journal, English - First TOF donors: Synthesis and characterization of dibenzo- and dinaphthotetraoxafulvalenes
K Tanaka; K Yoshida; T Ishida; A Kobayashi; T Nogami
ADVANCED MATERIALS, WILEY-V C H VERLAG GMBH, 12, 9, 661-+, May 2000, Peer-reviwed, Communication: Synthetic metals based on tetrachalcogenafulvalene donor molecules have received much attention. Unlike the thia-, selena-, and tellura-derivatives, tetraoxafulvalenes (TOFs) are rare, because of difficulties in their preparation and isolation. Here is presented the first unequivocal synthesis, spectral characterization, and X-ray structure determination of TOF derivatives-dibenzo-(see Figure) and dinaphtho-TOF.
Scientific journal, English - Low-temperature heat capacities and ferromagnetic phase transition of the organic free radical ferromagnet, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (CATMP)
Y Miyazaki; T Matsumoto; T Ishida; T Nogami; M Sorai
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 73, 1, 67-71, Jan. 2000, Peer-reviwed, Heat capacities of the organic free radical ferromagnet, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl(CATMP) have been measured in the temperature range between 0.1 and 311 K. A ferromagnetic phase transition was observed at 0.28 K and a heat capacity hump was found above the transition temperature. This hump is due to the short-range order characteristic of low-dimensional magnetic spin systems. The enthaly and entropy gains due to the ferromagnetic phase transition were estimated to be 4.06 J mol(-1) and 5.71 J K-1 mol(-1), respectively. This entropy agrees well with the theoretical value Rln 2 ( = 5.76 J K-1 mol(-1)) expected for the magnetic entropy of a spin system with the spin quantum number S = 1/2, where R is the gas constant. The heat capacity hump above the transition temperature is well accounted for in terms of the S = 1/2 two-dimensional ferromagnetic Heisenberg model of square lattice with the intralayer exchange interaction J/k(B) = 0.42 K, where the spin Hamiltonian H = - 2JS(i).S-j is adopted and k(B) stands for the Boltzmann constant. The analysis of the magnetic heat capacities below the transition temperature on the bar;is of the spin wave theory clarified that the magnetic system settles down in three-dimensional ferromagnetic order below the transition temperature with the interlayer exchange interaction J'/k(B) = 0.024 K.
Scientific journal, English - Spin density of a ferromagnetic TEMPO derivative: polarized neutron investigation and ab initio calculation
Y Pontillon; A Grand; T Ishida; E Lelievre-Berna; T Nogami; E Ressouche; J Schweizer
JOURNAL OF MATERIALS CHEMISTRY, ROYAL SOC CHEMISTRY, 10, 7, 1539-1546, 2000, Peer-reviwed, 4(p-Chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidine-N-oxyl is a ferromagnetic TEMPO derivative (T-c = 0.28 K) where the nearest and next nearest neighbour NO sites construct a two-dimensional network. We have determined the spin density in this compound by polarized neutron diffraction on a single crystal at low temperature. Most of the spin density (80%) has been found on the NO group, with an equal repartition between the two atoms. 20% of the spin density is delocalized on the rest of the molecule. As for the pure TEMPONE, the two carbon atoms neighbouring the nitrogen of the NO group carry significant spin populations of different signs: -0.074(12) for C3 and +0.069(17) for C4. This implies that the coupling mechanism is rather complex: it concerns many contacts including methyl hydrogens, but also methylene hydrogens, the imino nitrogen N2 and the terminal chlorine atom. Ab initio (DFT) calculations account correctly for the repartition of the spin density between nitrogen and oxygen, but they underestimate the part of the spin density which is delocalized and also the effects of the magnetic interactions on the spin populations of adjacent molecules.
Scientific journal, English - Magnetic phase transition of Py2N-- and NCNH--bridged nickel(II) complexes at about 25 K
K Zusai; T Katayama; T Ishida; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 343, 439-444, 2000, Peer-reviwed, Magnetic properties of nickel(II) complexes containing di(2-pyridyl)amine anion (dpa(-)) or cyanamide anion (ca(-)) are investigated. Ni/dpa complexes prepared from NiCl2 and Ni(NO3)(2) showed magnetic transition at 17 and 19 K, respectively. The Ni/ca complex prepared from NiCl2 showed magnetic transition at 25 K.
Scientific journal, English - Magnetism of pyrimidine-bridged metal(II) halide complexes
K Zusai; T Kusaka; T Ishida; R Feyerherm; M Steiner; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 343, 445-450, 2000, Peer-reviwed, Magnetic phase transitions of PM2. CoCl2, PM2. CoBr2, and PM2. FeCl2 (PM = pyrimidine) were observed at T-N = 4.4, 4.7, and 6.1 K, respectively, as defined by the peak of chi(ac)' They are characterized to be isomorphous, belonging to the space group I4(1)22, and canted antiferromagnets below TN The neutron diffraction study supports the principally antiferromagnetic structure.
Scientific journal, English - TEMPO radicals showing magnetic interactions. II. 4-(benzylideneamino)-TEMPO and related compounds
F Iwasaki; JH Yoshikawa; H Yamamoto; K Takada; E Kan-nari; M Yasui; T Ishida; T Nogami
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, MUNKSGAARD INT PUBL LTD, 55, 1057-1067, Dec. 1999, Peer-reviwed, X-ray crystal structure analyses were performed on 4-(Ar-methyleneamino)-TEMPO radicals at room temperature (TEMPO = 2,2,6,6-tetramethylpiperidyl-1-oxyl): Ar = Ph [4-(benzylideneamino)-2,2,6,6-tetra-methylpiperidyl-1-oxyl], 4-MeS-Ph [2,2,6,6-tetramethyl-4-(4-methylthiobenzylideneamino)piperidyl-1-oxyl], 4-Me-Ph [4-(4-methylbenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl], 4-PhO-Ph [2,2,6,6-tetramethyl-4-(4-phenoxybenzylideneamino)piperidyl-1-oxyl], 4-MeSO2-Ph [2,2,6,6-tetramethyl-4-(4-methylsulfonylbenzylideneamino)piperidyl-1-oxyl], 3-Py [2,2,6,6-tetramethyl-4-(3-pyridylmethylideneamino)piperidyl-1-oxyl] and 2-Naph [2,2,6,6-tetramethyl-4-(2-naphthylideneamino)piperidyl-1-oxyl]. Structures of Ph and 4-Me-Ph derivatives were also determined at 100 K. Some of these crystals have been revealed to show intermolecular ferromagnetic interactions at an extremely low temperature. Structural features of crystals of Ph, 4-MeS-Ph and 3-Py derivatives, which show ferromagnetic interactions, are very similar to each other. In these crystals, O atoms are arranged to form a sheet. The ferromagnetic interactions are considered to be transferred through O ... H van der Waals' interactions of the B-H atoms of the neighboring TEMPO rings within the sheet. Between O ... O sheets, the aryl groups are arranged in a herringbone manner. The crystal structure of the 4-Me-Ph derivative, which shows an antiferromagnetic interaction, is also pseudo-isostructural with those of Ph, 4-MeS-Ph and 3-Py derivatives, while the arrangement of the aryl groups is different. The packing mode of the crystals of the 4-MeSO2-Ph derivative, of which the Weiss constant theta is nearly zero, is very different from those of the other derivatives showing magnetic interactions. The fact that the crystal structure of the paramagnetic 4-MeSO2-Ph derivative does not show the O ... O sheet structure accompanying the O ...beta-H interactions indicates that the intermolecular ferromagnetic interactions through B-H atoms within the O ... O sheet are important for these TEMPO radical crystals.
Scientific journal, English - Dichlorobis(pyrimidine-N)cobalt(II) and its bromo derivative
D Hashizume; R Takayama; K Nakayama; T Ishida; T Nogami; M Yasui; F Iwasaki
ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS, MUNKSGAARD INT PUBL LTD, 55, 1793-1797, Nov. 1999, Peer-reviwed, The title compounds, [COCl2(C4H4N2)(2)] and [CoBr2(C4H4N2)(2)], show weak ferromagnetism below 5 K. The relationship between the magnetic properties and the structure is discussed. The crystals of the Cl and Br derivatives are isomorphous. The Co atom is coordinated with two halogen atoms and four N atoms of pyrimidine molecules at axial and equatorial positions, respectively, to form the octahedral geometry. The nearest neighbouring Co atoms are bridged by the pyrimidine molecules to form a three-dimensional network. As the pyrimidine molecules are considered to conduct antiferromagnetic interactions, the weak ferromagnetism may result from the chiral structure of the crystals.
Scientific journal, English - TEMPO radicals showing magnetic interactions. I. 4-(4-halobenzylideneamino)TEMPO and related compounds
F Iwasaki; JH Yoshikawa; H Yamamoto; E Kan-Nari; K Takada; M Yasui; T Ishida; T Nogami
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, MUNKSGAARD INT PUBL LTD, 55, 231-245, Apr. 1999, X-ray crystal structure analyses of the 4-(4-halobenzylideneamino)TEMPO (TEMPO = 2,2,6,6-tetramethyl-piperidyl-1-oxyl) radicals 4-(4-fluorobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, 4-(4-bromob enzylidene amino)-2,2,6,6-tetramethylpiperidyl-1-oxyl and 4-(4-iodobenzylideneamino)-2,2,6,6-tetramethylpiperidyl-1-oxyl, and other 4-Ar-CH=N-TEMPO [Ar = 4-Ph-Ph, 2,2,6,6-tetramethyl-4-(4-phenylbenzylideneamino)piperidyl-1-oxyl, 4-Py, 2,2,6,6-tetramethyl-4-(4-pyridylmethylideneamino)piperidyl-1-oxyl, and 3,5-diCl-Ph, 4-(3,5-dichlorobenzylideneamino) -2,2,6,6-tetramethylpiperidyl-1-oxyl] radicals have been performed at room temperature. Some of these radicals show intermolecular ferromagnetic interactions at extremely low temperatures. X-ray analysis revealed that crystals of the 4-I-Ph derivative showed two modifications [ (a) and (b)] measurements of the magnetic properties of these crystals showed a ferromagnetic transition at an extremely low temperature for modification (a) and an antiferromagnetic interaction for modification (b). The structural features of these TEMPO radical crystals can be classified into three groups: (i) the crystal structures of the 4-Cl-Ph, 4-I-Ph(a) and 4-Ph-Ph derivatives, which show a ferromagnetic transition; (ii) the structures of the 4-Br-Ph and 4-Py derivatives, which show a ferromagnetic interaction (theta > 0); (iii) miscellaneous: the antiferromagnetic 4-F-Ph and 4-I-Ph(b) derivatives (theta < 0) and the ferromagnetic 3,5-diCl-Ph (theta > 0) derivative. Sheetlike arrangements of O atoms and intra-sheet interactions through the CH2 or CH3 groups of the TEMPO rings are related to the mechanisms of the ferromagnetic interactions.
Scientific journal, English - Intermolecular ferromagnetic interaction in the crystal of a diphenyl nitroxide derivative. The role of spin-polarized hydrogen atoms located near a neighboring N-O site
M Nakagawa; T Ishida; M Suzuki; D Hashizume; M Yasui; F Iwasaki; T Nogami
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 302, 1-2, 125-131, Mar. 1999, Peer-reviwed, The crystal of 9,9-dipropyl-9,10-dihydroacridin-10-yloxyl exhibited a positive Weiss constant (+0.77 K) ascribable to a three-dimensional network of ferromagnetic interactions. The orbital orthogonality between the antibonding N-O pi * and H 1s orbitals was found in a nearly isosceles triangle geometry of neighboring H atoms and the N-O site. The following spin polarization scheme is proposed: drop N(up arrow)-C(down arrow)=C-o(up arrow)-C-m(down arrow)-H-m(up arrow) ... O-.(up arrow)-N drop, where o- and m-positions are defined with respect to the N-O group. (C) 1999 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Single Crystal Magnetic Susceptibility of 1-D [PM.Cu(NO3)2.(H2O)2]n
R. Feyerherm; T. Ishida; T. Nogami; M. Steiner
Molecular Crystals and Liquid Crystals, 335, 235-244, 1999, Peer-reviwed
International conference proceedings, English - Solid-state high-resolution H-1 and D-2 NMR study of the electron spin density distribution of the hydrogen-bonded organic ferromagnetic compound 4-hydroxyimino-TEMPO
G Maruta; S Takeda; R Imachi; T Ishida; T Nogami; K Yamaguchi
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 121, 2, 424-431, Jan. 1999, Peer-reviwed, The electron spin density distribution at hydrogen atoms of 4-hydroxyimino-2,2,6,6-tetramethylpiperidin-1-yloxyl (4-hydroxyimino-TEMPO), which has recently been shown to act as a molecular ferromagnet at low temperature, was determined in the crystalline phase on the basis of the temperature dependence of the Fermi contact shifts in the magic angle spinning deuterium NMR spectrum to elucidate the mechanism of intermolecular magnetic interaction. There are two kinds of close contacts among neighboring radical molecules in the crystalline phase. An axial methyl hydrogen atom locates near a neighboring N-O radical group, and the hydroxyl group undergoes hydrogen bonding with another neighboring N-O radical group. The plus and minus signs of the observed hyperfine coupling constants A(D) of methyl deuteriums indicate that there are two different mechanisms for the electron spin density distribution. Equatorial CD3 groups show negative coupling constants (A(D) = -0.24 MHz) induced by an intramolecular spin polarization mechanism, whereas the positive hyperfine coupling constants (A(D) = +0.12 MHz) of axial CD3 groups indicate that a single occupied MO spreads out partly toward the axial CD3 groups by hyperconjugation. The small positive hyperfine coupling constant of the axial methyl group is due to averaging of the one positive and two negative values of the three deuterium atoms of the methyl group caused by rapid rotation. The intermolecular magnetic interaction through the axial methyl group seems to be sensitive to the orientation of the methyl group and can be ferromagnetic in a crystal of 4-hydroxyimino-TEMPO. The large negative hyperfine coupling constant (A(D) = -0.45 MHz) observed for the NOD group strongly implies that hydrogen bonding mediates the intermolecular magnetic interaction in the crystalline phase. The present experimental results and molecular orbital calculations indicate that ferromagnetic interaction exists in the hydrogen-bonded chains running along the crystallographic c axis, and that the two chains can be considered to be coupled ferromagnetically through the axial methyl groups to form a double chain. In the directions of the crystallographic a and b axes, weak ferromagnetic interactions are expected on the basis of the measured spin density distributions of the deuterium atoms of the equatorial methyl and the methylene groups which participate in interchain contacts in the crystallographic a-b plane. The H-1 and D-2 NMR spectra measured for solutions demonstrated that the spin density distribution of the radical molecule changes dramatically between the solution and crystalline phases.
Scientific journal, English - Molecular Orbital Study on the Magnetic Properties of Pyrazine- and Pyrimidine-Bridged Copper(II) Complexes
F. Mohri; K. Yoshizawa; T. Yamabe; T. Ishida; T. Nogami
Molecular Engineering, 8, 357-373, 1999, Peer-reviwed
Scientific journal, English - Possible superhigh-spin cluster in the crystals of a novel nitronyl nitroxide radical as studied by FT pulsed ESR
D Shiomi; K Sato; T Takui; K Itoh; M Tamura; Y Nishio; K Kajita; M Nakagawa; T Ishida; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 335, 1071-1081, 1999, Peer-reviwed, Syntheses and magnetic properties of novel nitronyl nitroxide derivatives are reported. In the derivatives under study, the bulky tetramethylethylene group of the conventional nitronyl nitroxide has been replaced by aromatic rings, giving planar pi-conjugation systems. The first half of the paper is devoted to the syntheses and characterization of new derivatives of such radical, 2-phenylbenzimidazol-1-yl-N,N'-dioxide (PBIDO). Chemical stability, pi-spin density distribution, and solid state magnetic properties have been examined from solution ESR and static susceptibility measurements. In the latter half, we discuss an anomaly of paramagnetic relaxation found in crystals of PBIDO by pulsed ESR spectroscopy The origin of the anomaly is attributed to a possible formation of paramagnetic species with huge S, or "superhigh-spin cluster" at lattice defects in the crystal.
Scientific journal, English - Spin density of a ferromagnetic tempo derivative
Y Pontillon; T Ishida; E Lelievre-Berna; T Nogami; E Ressouche; J Schweizer
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 334, 359-367, 1999, Peer-reviwed, We have determined by polarized neutron diffraction the spin density of a ferromagnetic (Tc=0.28K) tempo derivative: the 4(p-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl, where the nearest and next nearest neighbours N-O sites construct a two-dimensional network parallel to the ((a) over right arrow,(b) over right arrow) plane. Most of the spin density lies on the N and O atoms of the NO radical and is equally shared between these two atoms. As for the pure tempone, the two carbon atoms neighbouring the nitrogen of the N-O group in the 6-member ring, carry significant spin populations of different signs: -0.074(12) for atom C3 and +0.063(17) for atom C4. This is not consistent with the coupling mechanism proposed previously which implied that the populations of both C3 and C4 should be negative. A tentative explanation for the coupling mechanisms, taking into account the spin density distribution, is discussed.
Scientific journal, English - Pressure effect of organic ferromagnetic radical crystal p-Cl-C6H4CH=N-TEMPO
M Mito; T Kawae; K Takeda; T Ishida; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 334, 323-332, 1999, Peer-reviwed, 4-(p-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-yloxyl) (p-Cl-C6H4CH=N-TEMPO) radical crystal is the organic bulk-ferromagnet with T-c(P-0)=0.28 K (P-0; ambient pressure). In realizing the ferromagnetic intermolecular interaction, the spin polarization on the hydrogen of the methyl moiety is considered to play an important role. We expected that the pressurization would change the environment around the methyl moiety, and influence the bulk-ferromagnetic transition. So we measured the ac magnetic susceptibility under the pressure up to 10.9 kbar. With increasing pressure, the periodical down-and-up of T-c(P) and the pressure-induced ferro- to antiferromagnetic transition were observed. These experimental results may suggest that the pressurization destroys the bulk-ferromagnetism of p-Cl-C6H4CH=N-TEMPO as in beta-phase p-NPNN, making the methyl moiety rotate.
Scientific journal, English - Single crystal magnetic susceptibility of 1-D [PM center dot Cu(NO3)(2)center dot(H2O)(2)](n)
R Feyerherm; T Ishida; T Nogami; M Steiner
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 335, 947-956, 1999, Peer-reviwed, Single crystal studies of the magnetic susceptibility of the chain compound [PM . Cu(NO3)(2).(H2O)(2)](n) (PM=pyrimidine) show that it is a good example of a uniform S=1/2 antiferromagnetic Heisenberg chain, characterised by a single exchange parameter 12Jl/k(B) = 36 K. The Cu g-tensor principal values are g/=2.34(2) and g(perpendicular to)=2.05(2). In the low-T region a divergent contribution to the susceptibility (Curie tail) is observed that exhibits a pronounced anisotropy. This Curie tail cannot be reconciled assuming chain defects or impurities as its origin. It rather appears intrinsic to the chains and associated with the relative canting of the local g-tensors of neighbouring Cu ions and the Dzialoshinski-Moriya interaction. Our study constitutes evidence for a staggered contribution to the susceptibility which has been predicted theoretically recently.
Scientific journal, English - Magnetic phase transition of copper complexes containing dmit or TCNQ anion
T Ishida; Y Kokubo; K Nakayama; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 335, 1035-1044, 1999, Peer-reviwed, Magnetic phase transitions were observed at 6 and 10 K for (Me4N)(2)[Cu-(dmit)(2)] (dmit(2-) = 1,3-dithiole-2-thione-4,5-dithiolate) and Cu-TCNQ salts (TCNQ = tetracyanoquino dimethane), respectively.
Scientific journal, English - Intermolecular ferromagnetic interaction in pi-conjugated nitroxide radical crystals
T Ishida; M Nakagawa; R Imachi; Y Akui; S Masaoka; M Suzuki; D Hashizume; M Yasui; F Iwasaki; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 334, 89-98, 1999, Peer-reviwed, The crystal of 9,9-dipropyl-9,10-dihydroacridin-10-yloxyl exhibited a positive Weiss constant (+0.77 K) due to a 3-D network of ferromagnetic interactions. The crystal of 6,6-bis(p-ethylphenyl)-5,6-dihydrophenanthridin-5-yloxyl was revealed to possess a ferromagnetic dimer structure with 2J/k(B)= +3.5 K. Several bisbiphenylyl nib-oxide radicals showed ferromagnetic interaction.
Scientific journal, English - Ferromagnetic and antiferromagnetic phases of 4-(4-iodobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-yloxyl
T Ishida; K Togashi; R Imachi; H Yamamoto; M Yasui; F Iwasaki; T Nogami
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 71, 11, 2583-2587, Nov. 1998, Peer-reviwed, Temperature dependences of d.c. magnetic susceptibilities and magnetizations were measured for two different crystallographic phases of 4-(4-iodobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-yloxyl. Intermolecular ferromagnetic (Weiss temperature theta = +0.71 K) and antiferromagnetic (theta = - 0.23 K) interactions were found for alpha- and beta-phases, respectively, in the magnetic measurements above 1.8 K; the former phase showed a bulk ferromagnetic transition at 0.28 K. Based on the X-ray crystallographic data, intermolecular magnetic interactions are discussed. In the alpha-phase crystal, NO-radical sites form two-dimensional zigzag sheets. The ferromagnetic interaction within the sheet can be interpreted in terms of a beta-hydrogen mechanism, ON(up arrow)-C-alpha(down arrow)-C-beta (up arrow)-H-beta(down arrow)...(up arrow)ON<, in which the magnetic interaction is transmitted by beta-hydrogens. A dimer structure was found in the beta-phase crystal, and direct exchange and/or dipole interactions between N-O radicals seem to be the main origin of the antiferromagnetic interaction.
Scientific journal, English - Electrical conductivities and crystal and band-electronic structures of a new phase of BEDT-TTF-bromide salt, (BEDT-TTF)(2)Br(H2O)(3)
MY Luo; T Ishida; A Kobayashi; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 96, 2, 97-102, Jul. 1998, Peer-reviwed, A new bromide salt of BEDT-TTF, (BEDT-TTF)(2)Br(H2O)(3), was obtained by an electrochemical crystallization of the tetrahydrofuran (THF) solution containing BEDT-TTF, malonic acid, and aqueous tetrabutylammonium hydroxide. Commercially available aqueous Bu4NOH contaminates Br-, which is the anion source of this salt. The temperature dependence of the electrical resistance showed a complex behavior, but the resistance decrease in the low temperature range suggests a metallic ground state down to 4.2 K. Its crystal structure belongs to the delta-type, the example of which was found for delta-(BEDT-TTF)(2)AuBr2. A tight-binding band structure calculation revealed a closed Fermi surface, characteristic of a two-dimensional band structure. (C) 1998 Elsevier Science S.A. All rights reserved.
Scientific journal, English - Pyrimidine-bridged cobalt(II) complexes with a chiral 3-D network showing weak ferromagnetism
K Nakayama; T Ishida; R Takayama; D Hashizume; M Yasui; F Iwasaki; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 6, 497-498, Jun. 1998, Peer-reviwed, The reaction of CoX2 (X = Br, Cl) and pyrimidine (PM) in H2O gave crystals of CoPM2X2. The crystal structure analysis revealed a chiral three-dimensional network of the Co(II) ions. Weak ferromagnetism with relatively large spontaneous magnetization was observed below 5 K for both compounds.
Scientific journal, English - Crystal Structures of 4-(4-Halobenzylideneamino)-TEMPO Radicals Showing Magnetic Interactions
Fujiko Iwasaki; Hazime Yamamoto; Joseph H. Yoshikawa; Kiwamu Takada; Eiji Kannari; Masanori Yasui; Takayuki Ishida; Takashi Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 313, 223-228, 1998, Peer-reviwed, X-ray crystal structure analyses were performed on 4-(4-halo-benzylidene-amino)-TEMPO radicals, as well as other 4-Ar-CH=N-TEMPO radicals (Ar = 4-Ph-Ph, 4-Py, Ph, 4-MeS-Ph, 3-Py and 4-Me-Ph), at room temperature. Some of these crystals have been revealed to show intermolecular ferromagnetic interactions at an extremely low temperature. X-ray studies revealed that the crystals of the 4-I-Ph derivative showed two modifications; one showed a ferromagnetic transition and the other showed an antiferromagnetic interaction. Structural features of these TEMPO crystals are mainly classified to four groups: 1) structures of Cl-Ph, I-Ph and Ph-Ph derivatives which show a ferromagnetic transition, 2) Br-Ph and 4-Py derivatives with a ferromagnetic interaction, 3) Ph, 4-MeS-Ph, 3-Py, 4-Me-Ph derivatives showing different kinds of magnetic interactions, and 4) others including antiferromagnetic F-Ph and I-Ph derivatives.
Scientific journal, English - Ferromagnetism of organic radical crystals of deuterated TEMPO derivatives
R Imachi; T Ishida; T Nogami; M Yasui; F Iwasaki; N Takeda; M Ishikawa
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 85, 1-3, 1743-1744, Feb. 1997, Peer-reviwed, Three perdeuterated 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) derivatives were synthesized and their magnetic properties were studied. The measurements of magnetic susceptibilities and magnetization curves down to 1.8 K did not show significant difference by deuterium substitution. The Curie temperature of 4-hydroxyimino-TEMPO did not change by deuterium substitution.
Scientific journal, English - Magnetic properties of pyrimidine-bridged copper(II) complexes
T Ishida; K Nakayama; M Nakagawa; W Sato; Y Ishikawa; M Yasui; F Iwasaki; T Nogami
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 85, 1-3, 1655-1658, Feb. 1997, Peer-reviwed, The magnetic measurements of [PM2 . Cu(NO3)(2)](n) (PM = pyrimidine) showed ferromagnetic interaction between the Cu(II) spins with J/k(B) = +0.89 K. On the other hand, those of PM2 . Cu(NO3)(2) .(H2O)(2) and [PM . Cu(NO3)(2) .(H2O)(2)](n) showed para- and antiferromagnetic behaviors respectively. The magnetic properties of pyrimidine-bridged Cu(hfac)(2) and Cu(ClO4)(2) complexes are also reported.
Scientific journal, English - Electrical conductivities of MOTT salts
K Yoshida; T Ishida; T Nogami; A Kobayashi
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 86, 1-3, 2135-2136, Feb. 1997, Peer-reviwed, The temperature dependences of electrical conductivities were measured for several ion-radical salts of MOTT [4,5-methylenedithio-4',5'-(2-oxatrimethylenedithio)tetrathiafulvalene]. MOTT salts containing octahedral anions exhibited metallic behavior down to 20-50 K. The metal-nonmetal transition of MOTT2AsF6 was suppressed by pressurization. The X-ray crystallographic analyses and band calculations based on the crystal structures clarified the quasi-one-dimensional nature of MOTT2AsF6 and MOTT2SbF6.
Scientific journal, English - TEMPO-based organic ferromagnets and metamagnets (TEMPO=2,2,6,6-tetramethylpiperidin-1-yloxyl)
T Nogami; T Ishida
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 296, 305-322, 1997, Peer-reviwed, We have studied the magnetic properties of a series of 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) radicals, among which eight ferromagnets and six metamagnets were found. Based on their crystal structures, a mechanism of intermolecular ferromagnetic coupling was proposed. The ferromagnetic interactions in the crystals of 4-(p-methylthiobenzylideneamino)-TEMPO and 4-benzylamino-TEMPO were explained by the proposed mechanism. The ferromagnetic transition of 4-(p-chlorobenzylideneamino)-TEMPO was confirmed by zero-field mu SR measurements.
Scientific journal, English - mu SR of the organic radical ferromagnet, 4-(p-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-yloxyl
R Imachi; T Ishida; T Nogami; S Ohira; K Nishiyama; K Nagamine
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 3, 233-234, 1997, Peer-reviwed, The presence of spontaneous magnetization in the crystal of the title radical below the Curie temperature (T-C) was confirmed by means of zero-field muon spin rotation and relaxation measurements. The T-C was determined to be 0.28 K. A critical magnetization exponent suggested the 3-dimensional ordering of the radical spins.
Scientific journal, English - Ferromagnetic dimer of pi-conjugated organic free radicals 9,9-bis(p-tolyl)-9,10-dihydroacridin-10-yloxyl
R Imachi; T Ishida; M Suzuki; M Yasui; F Iwasaki; T Nogami
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 8, 743-744, 1997, Peer-reviwed, The magnetic property of the title radical crystals was analyzed by the Bleaney-Bowers equation with J/k(B) = +8.85 K, which is consistent with the dimeric molecular arrangement with ''pseudo-ortho'' stacking determined by crystallographic analysis. The inter-dimer interaction was antiferromagnetic.
Scientific journal, English - Ferromagnetic interaction in a pyrimidine-bridged copper(II) nitrate complex
K Nakayama; M Nakagawa; T Ishida; Y Ishikawa; M Yasui; F Iwasaki; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 306, 379-384, 1997, Peer-reviwed, Linear polymeric complexes [PM2.Cu(NO3)(2)](n) (PM = pyrimidine) and [L.Cu(hfac)(2)](n) (L = PM, 4- and 5-methylpyrimidine, and quinazoline) have been synthesized and characterized. The copper(II) spins were ferromagnetically coupled for all cases.
Scientific journal, English - Magnetic interaction via β-hydrogen atoms in tempo derivatives
Takashi Kawakami; Akifumi Oda; Sadamu Takeda; Wasuke Mori; Takayuki Ishida; Masanori Yasui; Fujiko Iwasaki; Takashi Nogami; Kizashi Yamaguchi
Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals, 306, 141-150, 1997, Peer-reviwed, Theoretical studies of the ferromagnetic property of phenyl-CH=N-TEMPO were carried out. The effective exchange integrals (Jab) were calculated for the nearest neighbour molecules in the crystal and the ferromagnetic interaction was revealed. To study the role of the hydrogen atoms, modified pair models were considered. It was concluded that the bridged ̈-hydrogen atoms dominantly contribute to the ferromagnetic interaction in the phenyl-CH=N-TEMPO crystal.
Scientific journal, English - Solid state H-1-MAS-NMR and spin densities on protons of the organic ferromagnetic TEMPO derivatives
G Maruta; S Takeda; T Kawakami; W Mori; R Imachi; T Ishida; T Nogami; K Yamaguchi
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 306, 307-314, 1997, Peer-reviwed, Electron spin densities on hydrogen atoms of 4-(arylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyls (abbreviated as Ar-CH=N-TEMPO), which show ferromagnetic behavior at low temperatures, were determined in their crystal phases from the temperature dependence of the Fermi contact shift measured by high speed magic angle spinning proton nuclear magnetic resonance. This method revealed a large negative hyperfine coupling constant for the methyl and methylene protons, A = -1.00 MHz for Ar = p-Cl-ph and A = -1.32 MHz for Ar = ph, and very small one for the aryl group protons, /A/ < 0.01 MHz for p-Cl-ph and A = +0.04 MHz for ph. The observed negative hyperfine coupling constant (negative spin density) of methyl and methylene protons matches with spin alternation for the intermolecular spin polarization mechanism through the contact of methyl and/or methylene protons to adjacent N-O radical group. This contact potentially contributes to the intermolecular ferromagnetic interaction.
Scientific journal, English - Organic radicals exhibiting intermolecular ferromagnetic interactions with high probability: 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls and related compounds
K Togashi; R Imachi; K Tomioka; H Tsuboi; T Ishida; T Nogami; N Takeda; M Ishikawa
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 69, 10, 2821-2830, Oct. 1996, Peer-reviwed, A series of 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls (4-arylmethyleneamino-TEMPO) and related compounds were synthesized, and their magnetic susceptibilities were measured by a SQUID magnetometer in the temperature range of 1.8-100 K. Of 165 radicals investigated, 52 kinds of radicals exhibited intermolecular ferromagnetic interactions. These were confirmed by the increase of effective magnetic moments in low-temperature regions. Positive Weiss temperatures (theta), ranging from +0.03 to +0.75 K, were found for these materials. Over 100 kinds of radicals exhibited antiferromagnetic interactions with theta ranging from -0.01 to -24 K. The surprisingly high probability of finding organic radicals with intermolecular ferromagnetic interaction may be understood by the characteristic molecular arrangements in the crystals. An oxygen atom of an NO radical site of a piperidin-1-yloxyl moiety is apt to locate near methyl- and/or methylene-hydrogens of beta-positions of the adjacent molecules, and the resultant spin polarization gives rise to parallel spin alignments of nearest NO sites in the crystals. 4-(4-Iodophenylmethyleneamino)-TEMPO exhibited a bulk ferromagnetic transition at 0.4 K. Six radicals exhibited metamagnetic transitions at magnetic fields lower than 200 Oe below 0.1 K.
Scientific journal, English - Proposed mechanism of ferromagnetic interaction of organic ferromagnets: 4-(Arylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyls and related compounds
T Nogami; T Ishida; M Yasui; F Iwasaki; N Takeda; M Ishikawa; T Kawakami; K Yamaguchi
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 69, 7, 1841-1848, Jul. 1996, Peer-reviwed, A possible mechanism of ferromagnetic coupling of a series of organic radical ferromagnets is presented, based on their crystal structures and molecular-orbital calculations. The investigated radicals are 4-(arylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyls (abbreviated as Ar-CH=N-TEMPO, where Ar = phenyl, 4-methylthiophenyl, 4-chlorophenyl, 4-biphenylyl, and 4-phenoxyphenyl), and 4-hydroxyimino-TEMPO. All of these radical crystals have characteristic features that oxygen atoms of N-O radical sites of TEMPO moieties always locate near methyl- and/or methylene-hydrogens at beta-positions of N-O in the TEMPO moieties of adjacent molecules. A positive spin on the N-O radical induces negative spins on the beta-hydrogen atoms due to an intramolecular spin-polarization, ON(dagger)-C(down arrow)-C(up arrow)-H(down arrow), which in turn induces a positive spin on the N-O sites of the adjacent molecules. This spin-alternation mechanism of ferromagnetic coupling among N-O sites via hydrogen bridges is also applicable to the case of an organic metamagnet, bis(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl) 1,6-hexanedicarboxylate. In the case of an organic ferromagnet, 2,4,6,8-tetramethyl-1,5-diazaadamantane-1,5-dioxyl, both the spin-alternation and direct exchange mechanisms seem to be operative.
Scientific journal, English - Unusual reactions of C-60 with aldehydes in the presence of aqueous ammonia
A Komori; M Kubota; T Ishida; H Niwa; T Nogami
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 37, 23, 4031-4034, Jun. 1996, Peer-reviwed, Fullerene C-60 reacts with alkylaldehydes in the presence of aqueous ammonia to give 2,5-dialkyl-substituted pyrrolidine derivatives. The reaction of phenylacetaldehyde under similar conditions afforded C-60(H)(CH(2)Ph) via possible decarbonylation. On the basis of the product analysis, reaction mechanisms are proposed in which C-60 plays the role of a dipolarophile or radical scavenger. (C) 1996 Elsevier Science Ltd.
Scientific journal, English - Synthesis and characterization of C-60 derivatives possessing TEMPO radicals
T Ishida; K Shinozuka; T Nogami; M Kubota; M Ohashi
TETRAHEDRON, PERGAMON-ELSEVIER SCIENCE LTD, 52, 14, 5103-5112, Apr. 1996, Peer-reviwed, The sodium salt of TEMPON tosylhydrazone was pyrolyzed in chlorobenzene in the presence of C-60 to give the adducts C-60(TEMPO)(n) (n = 1-3) [TEMPO = 2,2,6,6-tetramethyl piperidin-1-oxyl, TEMPON = 4-oxo-TEMPO]. The adducts were isolated by means of gel permeation chromatography, and characterized by mass, IR, UV/V is, and ESR spectroscopies. The structure of C-60(TEMPO) was determined to be an open [5,6] adduct. The magnetic measurements ensured the radical purity. (C) 1996 Elsevier Science Ltd
Scientific journal, English - Synthesis, structure, and some reactions of (2,4,6-tri-t-butyl)thiobenzaldehyde, the first stable aromatic thioaldehyde
A Ishii; T Ishida; N Kumon; N Fukuda; H Oyama; N Inamoto; F Iwasaki; R Okazaki
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 69, 3, 709-717, Mar. 1996, Peer-reviwed, The title compound 1 was synthesized by the reaction of 2,4,6-tri-t-butylphenyllithium with O-ethyl thioformate or that of 2,4,6-tri-t-butylbenzaldehyde hydrazone with disulfur dichloride in the presence of triethylamine. The thioaldehyde 1 is a purple crystalline compound which is thermally quite stable; only around 200 degrees C it underwent intramolecular cyclization to give 6,8-di-t-butyl-3,4-dihydro-1,4-dimethyl 9. The X-ray crystallographic analysis of 1 revealed that the thioformyl group is almost perpendicular to the aromatic ring. The reaction of 1 with 1-cyano-1-methylethyl radicals afforded 9, while that with t-butyl radicals gave 1,3,5-tri-t-butyl-2-t-butylthiomethylbenzene and t-butyl 2,2-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-dien-2-yl)propyl sulfide in addition to 9. Some Grignard reagents and organolithiums reacted with 1 gave carbophilic, thiophilic, double addition products and some others depending on the kind of the organometallic reagents. Hydrazine and butylamine reacted with 1 very readily to give the corresponding hydrazone and imine, respectively.
Scientific journal, English - Crystal Structures of TEMPO Radicals Showing Ferromagnetic Interaction
M. Yasui; H. Yoshikawa; H. Yamamoto; T. Ishida; T. Nogami; F. Iwasaki
Molecular Crystals and Liquid Crystals, 279, 77-85, 1996, Peer-reviwed
International conference proceedings, English - Magnetic properties of 4- and 5-methylpyrimidine-bridged copper(II) complexes
M Nakagawa; Y Ishikawa; T Kogane; T Ishida; M Yasui; F Iwasaki; T Nogami
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 285, 351-356, 1996, Peer-reviwed, The magnetic measurements of [L . Cu(hfac)(2)](n) (L = 4- and 5-MPM, MPM = methylpyrimidine) revealed the presence of ferromagnetic interactions among Cu(II) spins. However, Cu spins in di- and trinuclear complexes were proved to be paramagnetic. The crystal structures of [4-MPM . Cu(hfac)(2)](n) and (4-MPM) (2) .[Cu(hfac)(2)](3) were determined.
Scientific journal, English - Synthesis and characterization of dialkyl-C61(+)
M Kawasumi; T Ishida; T Nogami
FULLERENE SCIENCE AND TECHNOLOGY, MARCEL DEKKER INC, 4, 3, 357-367, 1996, Peer-reviwed, Three-step synthesis from dialkyl ketone (R(2)C=O) with C-60 gave C-60(CR(2))(n) [R = Me, Et, Pr, Bu, (CH2)(5); n = 1, 2]. The adducts were isolated by means of gel permeation chromatography, and the monoadducts were characterized by H-1 and/or C-13 NMR spectroscopies as a mixture of major [5,6] and minor [6;6] isomers. Their solubility and electrochemical properties were reported.
Scientific journal, English - Ferromagnetism of pyrimidine-bridged copper(II) complexes
T Ishida; T Nogami; M Yasui; F Iwasaki; H Iwamura; N Takeda; M Ishikawa
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP, 278, A87-A96, 1996, Peer-reviwed, The magnetic measurements of polymeric complexes [L . Cu(hfac)(2)](n), (L = pyrimidine, 4-methylpyrimidine, and quinazoline) revealed the presence of ferromagnetic interactions among the copper spins. The X-ray crystal-structure analysis of the pyrimidine and quinazoline complexes showed a copper-ligand alternating chain. The ferromagnetic transition of the quinazoline complex was observed at about 0.12 K. Pyrimidine(2)-Cu(ClO4)(2) complex was found to be a ferromagnet with a transition temperature of about 10 K.
Scientific journal, English - Ferromagnetism of organic radical crystals of TEMPO derivatives
T Nogami; T Ishida; M Yasui; F Iwasaki; H Iwamura; N Takeda; M Ishikawa
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 278, A97-A106, 1996, Peer-reviwed, Several TEMPO-based radicals were found to be bulk ferromagnets with T-C of 0.2 - 0.4 K, as indicated by the measurements of ac magnetic susceptibilities and magnetization curves. On the basis of the X-ray crystal structure analysis, a possible mechanism of ferromagnetic interactions between neighboring N-O sites is proposed, in which the methyl or methylene groups play a role of ferromagnetic exchange couplers. New organic ferromagnets, 4-(p-methylthiobenzylideneamino)-TEMPO, 4-(benzylamino)-TEMPO, and 4-(hydroxyimino)-TEMPO as well as several metamagnets are reported.
Scientific journal, English - CRYSTAL STRUCTURES OF TEMPO RADICALS SHOWING FERROMAGNETIC INTERACTIONS.
H. Yamamoto; H. Yoshikawa; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, INT UNION CRYSTALLOGRAPHY, 52, C451-C451, 1996, Peer-reviwed
International conference proceedings, English - Magnetic Properties of 4- and 5-Methylpyrimidine-Bridged Copper(II) Complexes
M. Nakagawa; Y. Ishikawa; T. Kogane; T. Ishida; M. Yasui; F. Iwasaki; T. Nogami
Molecular Crystals and Liquid Crystals, 286, 29-34, 1996, Peer-reviwed
International conference proceedings, English - Ferromagnetism of organic radical crystals of TEMPO derivatives
T Nogami; T Ishida; M Yasui; F Iwasaki; H Iwamura; N Takeda; M Ishikawa
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 278, A97-A106, 1996, Peer-reviwed, Several TEMPO-based radicals were found to be bulk ferromagnets with T-C of 0.2 - 0.4 K, as indicated by the measurements of ac magnetic susceptibilities and magnetization curves. On the basis of the X-ray crystal structure analysis, a possible mechanism of ferromagnetic interactions between neighboring N-O sites is proposed, in which the methyl or methylene groups play a role of ferromagnetic exchange couplers. New organic ferromagnets, 4-(p-methylthiobenzylideneamino)-TEMPO, 4-(benzylamino)-TEMPO, and 4-(hydroxyimino)-TEMPO as well as several metamagnets are reported.
Scientific journal, English - AN ORGANIC METAMAGNET - 4-(2-NAPHTYLMETHYLENEAMINO)-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
T ISHIDA; K TOMIOKA; T NOGAMI; H YOSHIKAWA; M YASUI; F IWASAKI; N TAKEDA; M ISHIKAWA
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 247, 1-2, 7-12, Dec. 1995, Peer-reviwed, Magnetic measurements on the organic radical crystal of 4-(2-naphthylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl exhibited a Neel transition at about 0.12 K (T-N) and a metamagnetic transition below T-N (the coercive field was around 180 Oe at 40 mK). X-ray crystallographic analysis revealed that the molecules were arranged to give an almost columnar structure with the nearest intermolecular O...O distance of 5.70 Angstrom. The magnetic property was analyzed on the basis of the crystal structure.
Scientific journal, English - FULLERENE SPIN-LABEL - SYNTHESIS AND CHARACTERIZATION OF THE [60]FULLERENE-SUBSTITUTED TEMPO RADICAL
T ISHIDA; K SHINOZUKA; M KUBOTA; M OHASHI; T NOGAMI
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 18, 1841-1842, Sep. 1995, Peer-reviwed, A spin-labelled reagent C-60(TEMPO) (TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl) is synthesized, purified by LC, and characterized by spectroscopic, magnetic and electrochemical measurements.
Scientific journal, English - FERROMAGNETISM IN ORGANIC RADICAL CRYSTAL OF 4-(P-CHLOROBENZYLIDENEAMINO)-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
T NOGAMI; T ISHIDA; H TSUBOI; H YOSHIKAWA; H YAMAMOTO; M YASUI; F IWASAKI; H IWAMURA; N TAKEDA; M ISHIKAWA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 8, 635-636, Aug. 1995, Peer-reviwed, The magnetic measurements of the polycrystalline sample of the title radical exhibited a ferromagnetic phase transition at about 0.4 K. The relationship between the magnetic properties and crystal structures for derivatives possessing H, Br, or Ph in place of Cl is discussed. A possible mechanism of the ferromagnetic couplings was proposed.
Scientific journal, English - FIRST X-RAY STRUCTURAL DETERMINATION OF FULLERENE [2+2] CYCLOADDUCT
T ISHIDA; K SHINOZUKA; T NOGAMI; S SASAKI; M IYODA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 4, 317-318, Apr. 1995, Peer-reviwed, X-Ray crystallographic analysis of a 1:1 adduct of C-60 and 4,5-dimethoxybenzyne exhibited a benzocyclobutene structure given by [2+2] cycloaddition reaction at a 6,6-ring junction. A fullerene C(sp(3))-C(sp(3)) bond length is 1.645(8) Angstrom. Relatively shore intermolecular C...C, C...O, and C...S distances were found, where sulfur atoms belong to CS2 molecules enclosed.
Scientific journal, English - NEW ORGANIC FERROMAGNETS - 4-ARYLMETHYLENEAMINO-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL (ARYL=PHENYL, 4-BIPHENYLYL, 4-CHLOROPHENYL, AND 4-PHENOXYPHENYL)
T NOGAMI; K TOGASHI; H TSUBOI; T ISHIDA; H YOSHIKAWA; M YASUI; F IWASAKI; H IWAMURA; N TAKEDA; M ISHIKAWA
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 71, 1-3, 1813-1814, Apr. 1995, Peer-reviwed, The title radicals were found to be bulk ferromagnets, as indicated by the sharp divergence of the ac susceptibility. Their transition temperatures were found in the range of 0.2-0.4 K. The X-ray crystal structure analysis of the phenyl, biphenylyl, and chlorophenyl derivatives at room temperature revealed that the crystal consisted of an almost two-dimensional network of the N-O sites. In the case of aryl = 2-naphthyl, metamagnetic behavior was observed below about 0.3 K.
Scientific journal, English - INTRAMOLECULAR AND INTERMOLECULAR FERROMAGNETIC INTERACTION OF TRANSITION-METAL COMPLEXES CONTAINING PYRIMIDINE OR PYRAZINE DERIVATIVES
T ISHIDA; S MITSUBORI; T NOGAMI; Y ISHIKAWA; M YASUI; F IWASAKI; H IWAMURA; N TAKEDA; M ISHIKAWA
SYNTHETIC METALS, ELSEVIER SCIENCE SA, 71, 1-3, 1791-1792, Apr. 1995, Peer-reviwed, The 1/2 spins of oxovanadium(IV) ions were ferromagnetically coupled with J/k(B) = +1.1 similar to+2.7 K in the dinuclear complexes L[VO(hfac)(2)](2) (hfac = hexafluoroacetylacetonate, L = pyrimidine derivatives). Among them, a ferromagnetic transition was observed at about 0.14 K in PM[VO(hfac)(2)](2) (PM = pyrimidine). The polymeric complex QZ[Cu(hfac)(2)] (QZ = quinazoline) gave a positive Weiss constant (+0.39 K). The ferromagnetic transition was observed at about 0.12 K.
Scientific journal, English - SYNTHESIS AND SPECTRAL CHARACTERIZATION OF DIFUNCTIONAL FULLERENES
T ISHIDA; K TANAKA; T FURUDATE; T NOGAMI; M KUBOTA; S KURONO; M OHASHI
FULLERENE SCIENCE AND TECHNOLOGY, MARCEL DEKKER INC, 3, 1, 85-92, 1995, Peer-reviwed, The oxidation of C-60 with m-chloroperbenzoic acid gave C60O2 with a high positional selectivity, as the C-13 NMR analysis suggested. Diadducts C60CCl2O, C60CCl2(anthracene), C60CCl2[ (CH2CH2)(2)N-2], and C60CCl2[Pt(PPh(3))(2)] were synthesized, isolated, and characterized by negative ion FAB mass spectroscopy.
Scientific journal, English - SYNTHESIS AND MASS-SPECTRAL ANALYSIS OF C-60-DIHALOCARBENE ADDUCTS
T ISHIDA; T FURUDATE; T NOGAMI; M KUBOTA; T HIRANO; M OHASHI
FULLERENE SCIENCE AND TECHNOLOGY, MARCEL DEKKER INC, 3, 4, 399-409, 1995, Peer-reviwed, The monoadducts of C-60 with dibromo-, bromochloro-, and diiodocarbenes were synthesized and characterized. The mass spectra (MS) of C(60)CXY (X,Y = Cl, CI; Br, Br; and Br, Cl) were measured by the FAB, ESI, MALDI, and LD methods. The LDMS revealed that oligomerization reaction occurred to exhibit signals ascribable to C-2n (2n = 122 - 132 and 184 - 196).
Scientific journal, English - SYNTHESES AND STRUCTURES OF NOVEL FUSED-RING SYSTEMS CONTAINING 6 OR 7 SULFUR-ATOMS - 2,3/5,6-BIS(ETHYLENEDITHIO)THIENO[3,2-B]THIOPHENE AND 3,4/6,7-BIS(ETHYLENEDITHIO)THIENO[3,2-C][1,2]DITHIIN
M TANAKA; T ISHIDA; T NOGAMI; H YOSHIKAWA; M YASUI; F IWASAKI
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 68, 4, 1193-1199, 1995, Peer-reviwed, Novel fused-ring molecules, 2,3:5,6-bis(ethylenedithio)thieno[3,2-b]thiophene and 3,4:6,7-bis(ethylenedithio)thieno[3,2-c][1,2]dithiin, were synthesized for the development of new conducting organic salts. They have six and seven sulfur atoms, respectively. Their molecular and crystal structures were determined by Xray crystallographic analyses. Their oxidation potentials were measured, compared with those of the related donor molecules, and analyzed by a molecular-orbital calculation.
Scientific journal, English - SYNTHESIS AND STRUCTURE OF NITRENE-C-60 ADDUCT, C(60)NPHTH (PHTH=PHTHALIMIDO)
SY KUWASHIMA; M KUBOTA; K KUSHIDA; T ISHIDA; M OHASHI; T NOGAMI
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 35, 25, 4371-4374, Jun. 1994, Peer-reviwed, Phthalimidonitrene (:NPhth) generated from H(2)NPhth and lead tetraacetate in chlorobenzene was found to add to C-60, affording C-60(NPhth)(n) (n=1-4). The adducts were separated, and the mono-adduct was spectroscopically characterized as an aziridine structure at a 6/6-ring junction. The electron affinity and aziridine inversion are significantly influenced by the substituents on the aziridine nitrogen.
Scientific journal, English - AN ORGANIC FERROMAGNET WITH A T-C OF 0.4 K - 4-(P-PHENYLBENZYLIDENEAMINO)-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
T ISHIDA; H TSUBOI; T NOGAMI; H YOSHIKAWA; M YASUI; F IWASAKI; H IWAMURA; N TAKEDA; M ISHIKAWA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 5, 919-922, May 1994, Peer-reviwed, The polycrystalline sample of the title radical has a positive Weiss constant of 0.63 K. The ac susceptibility measurements indicated a ferromagnetic phase transition at about 0.4 K. The magnetization measured at 80 mK (below T-c) showed a characteristic curve of a ferromagnet with a small hysteresis. The X-ray crystal structure analysis at room temperature revealed a two-dimensional network of the N-O sites (O...O distances are 5.96 and 6.09 Angstrom) with an inter-sheet distance of 14.2 Angstrom.
Scientific journal, English - ORGANIC 2ND-ORDER NONLINEAR-OPTICAL MATERIALS WITH TRANSPARENCY IN THE BLUE WAVELENGTH REGION - ETHYLENE DERIVATIVES POSSESSING ELECTRON-DONOR AND ACCEPTOR GROUPS
H OSAKA; T ISHIDA; T NOGAMI; R YAMAZAKI; M YASUI; F IWASAKI; A MIZOGUCHI; M KUBATA; T UEMIYA; A NISHIMURA
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 67, 4, 918-923, Apr. 1994, Peer-reviwed, A series of ethylene and methanimine derivatives possessing both electron-donor and -acceptor groups were synthesized in order to obtain frequency doublers of infrared semiconductor lasers. Their second-harmonic-generation (SHG) was investigated by means of a powder method and an electric-field-induced second-harmonic method. Three ethylene derivatives were found to be SHG active without any absorption in the blue wavelength region. X-Ray crystallographic analyses were made for two of them. It was found that strong donor and acceptor substituents tend to twist the central C=C double bond, thereby resulting in smaller beta-values than those expected for non-twisted molecular structures. Based on the molecular and crystal structures, some strategies are presented regarding the synthesis of SHG materials of these push-pull ethylenes and methanimines.
Scientific journal, English - MOLECULAR FERROMAGNET, PM[VO(HFAC)(2)](2)(PM=PYRIMIDINE, HFAC=1,1,1,5,5,5-HEXAFLUOROPENTA-2,4-DIONATE) - FERROMAGNETIC ASSEMBLY OF GROUND HIGH-SPIN MOLECULES
S MITSUBORI; T ISHIDA; T NOGAMI; H IWAMURA; N TAKEDA; M ISHIKAWA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 4, 685-686, Apr. 1994, Peer-reviwed, A ferromagnetic transition was observed at about 0.14 K in the molecular crystals of the title complex. The isothermal magnetization measured at 85 mK (below T-c) showed an S-shaped curve characteristic of a ferromagnet with a small hysteresis. The present system realizes the high-spin molecule toward molecular-based ferromagnets.
Scientific journal, English - FULLERENE AZIRIDINE - FACILE SYNTHESIS AND SPECTRAL CHARACTERIZATION OF FULLERENE URETHANE, C60NCO2CH2CH3
T ISHIDA; K TANAKA; T NOGAMI
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 3, 561-562, Mar. 1994, Peer-reviwed, A fullerene urethane, C60NCO2CH2CH3, was obtained by a one-pot reaction from C-60, NaN3, ClCO2CH2CH3, and 15-crown-5 ether in refluxing, toluene. The structure of the product was spectroscopically determined as a closed aziridine at a 6/6-ring junction.
Scientific journal, English - PYRIMIDINES AS FERROMAGNETIC EXCHANGE COUPLERS IN DINUCLEAR OXOVANADIUM(IV) COMPLEXES
S MITSUBORI; T ISHIDA; T NOGAMI; H IWAMURA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 2, 285-288, Feb. 1994, Peer-reviwed, The intramolecular magnetic interactions between 1/2 spins of two oxovanadium (IV) ions were studied in the complexes L[VO(hfac)(2)](2) (hfac=hexafluoroacetylacetonate, L=4-methyl-, 4,6-dimethyl-, 4-amino- and unsubstituted-pyrimidines, and quinazoline). The magnetic measurements revealed that the vanadium spins were ferromagnetically coupled through the pyrimidine bridges with J/k(B)=1.1-2.7 K. The intermolecular ferromagnetic interaction was found in the case of L=pyrimidine.
Scientific journal, English - A NEW ORGANIC FERROMAGNET - 4-BENZYLIDENEAMINO-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
T NOGAMI; K TOMIOKA; T ISHIDA; H YOSHIKAWA; M YASUI; F IWASAKI; H IWAMURA; N TAKEDA; M ISHIKAWA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 1, 29-32, Jan. 1994, Peer-reviwed, An organic radical crystal of 4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl was found to be a bulk ferromagnet, as indicated by the divergence of the ac susceptibility at 0.18 K and by the magnetic hysteresis below this temperature. The X-ray crystal structure analysis at room temperature revealed that the crystal consisted of an almost two-dimensional network of the N-O sites.
Scientific journal, English - SPECTRAL CHARACTERIZATION OF ANTHRACENE-C60, CYCLOPENTADIENE-C60, AND DICHLOROCARBENE-C60 ADDUCTS
T ISHIDA; M TSUDA; T NOGAMI; S KURONO; M OHASHI
FULLERENE SCIENCE AND TECHNOLOGY, MARCEL DEKKER INC, 2, 2, 155-164, 1994, Peer-reviwed, We studied cycloaddition reactions of C60 with typical dienes and dichlorocarbene. The title products were isolated by HPLC and characterized by negative ion FAB mass spectroscopy. C-13 NMR analyses suggest that all of the adducts investigated here have the closed structures at the 6-ring/6-ring junction.
Scientific journal, English - SYNTHESIS AND CHARACTERIZATION OF C60 ADDUCTS WITH BENZYNE, DICHLOROCARBENE, DIENES, AND OXYGEN
T NOGAMI; M TSUDA; T ISHIDA; S KURONO; M OHASHI
ADVANCED MATERIALS '93, I - A & B, ELSEVIER SCIENCE PUBL B V, 14, A & B, 1181-1184, 1994, Peer-reviwed
International conference proceedings, English - C61CL2 - SYNTHESIS AND CHARACTERIZATION OF DICHLOROCARBENE ADDUCTS OF C-60
M TSUDA; T ISHIDA; T NOGAMI; S KURONO; M OHASHI
TETRAHEDRON LETTERS, PERGAMON-ELSEVIER SCIENCE LTD, 34, 43, 6911-6912, Oct. 1993, Peer-reviwed, Dichlorocarbene generated by pyrolysis of sodium trichloroacetate was found to add to C60 in a benzene-diglyme mixed solvent. The products C60(CCl2)n (n= 1-3) were isolated by means of gel permeation chromatography eluted with toluene and characterized by FAB mass spectroscopy. The structure Of C60(CC12) was determined by C-13 NMR spectroscopy The addition occurred at the 6-ring/6-ring junction, giving a cyclopropane structure.
Scientific journal, English - ISOLATION AND CHARACTERIZATION OF DIELS-ALDER ADDUCTS OF C-60 WITH ANTHRACENE AND CYCLOPENTADIENE
M TSUDA; T ISHIDA; T NOGAMI; S KURONO; M OHASHI
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 16, 1296-1298, Aug. 1993, Peer-reviwed, The cycloadducts of C60 and typical dienes have been isolated by HPLC, and the anthracene and cyclopentadiene adducts characterized by FAB mass and NMR spectroscopy.
Scientific journal, English - INTERMOLECULAR FERROMAGNETIC INTERACTION OF 4-BENZYLIDENEAMINO-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
K TOMIOKA; S MITSUBORI; T ISHIDA; T NOGAMI; H IWAMURA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 7, 1239-1242, Jul. 1993, Peer-reviwed, The magnetic properties of a polycrystalline sample of the title compound were studied on a SQUID magnetometer. The intermolecular ferromagnetic interaction was indicated by the upward deviation of the magnetization curves from a Brillouin function with S=1/2 below 16 K and by the increasing effective moment with decreasing temperature. The Weiss constant was + 0.7 K. The radicals possessing a 9-anthryl or 3-perylenyl group in place of the phenyl group showed anitiferromagnetic interaction.
Scientific journal, English - INTERMOLECULAR FERROMAGNETIC INTERACTION OF 4-(2-NAPHTHYLMETHYLENEAMINO)-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
K TOMIOKA; T ISHIDA; T NOGAMI; H IWAMURA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 4, 625-626, Apr. 1993, Peer-reviwed, The magnetic susceptibility and magnetization of a polycrystalline sample of the title compound were measured on a Faraday balance and a SQUID susceptometer. The intermolecular ferromagnetic interaction was indicated by the facts that the (chi(mol))T value increased with decreasing temperature and that the magnetization measured at 1.7 and 4.2 K saturated more rapidly than that of a Brillouin function with S = 1/2.
Scientific journal, English - SYNTHESES, 2ND-ORDER NLO PROPERTIES, AND CRYSTAL-STRUCTURES OF TETRA-SUBSTITUTED ETHYLENE, TRI-SUBSTITUTED SCHIFF-BASE, AND DIPHENOXYMETHANE DERIVATIVES
T ISHIDA; H OSAKA; T NOGAMI; R YAMAZAKI; M YASUI; F IWASAKI; A MIZOGUCHI; M KUHATA; T UEMIYA; A NISHIMURA
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 56, 1, 2013-2018, Mar. 1993, Peer-reviwed, In order to obtain frequency doubler of the infrared semiconductor lasers, a series of push-pull ethylenes were synthesized. Among them, ethyl 2,2-bis(methylthio)-1'-cyanoacrylate, ethyl 2-dimethylamino-2-methylthio-1-cyanoacrylate, and 2-dimethylamino-2-methylthio-1-cyanoacrylo-nitrile gave SHG with intensities of 5.5, 0.8, and 0.5 times, respectively, that of urea by a powder technique using an Nd:YAG laser as a fundamental wave. Their absorption edges located below 370 nm. The crystal structure analysis showed the distorted ethylene structure mainly due to the contribution of an intramolecular charge-transfer in their ground states. Their beta values were calculated in an MNDO level. Diphenoxymethanes are expected to be LAMBDA-shaped molecules and to favor columnar and non-centrosymmetric structures when packed in a crystal. Bis[p-(2,2-dicyanovinyl)phenoxy]methane, bis[p-(2-cyano-2-ethoxycarbonylvinyl)phenoxy]methane, and bis(pbromophenylthio)methane gave SHG intensities 0.4, 1.4, and 0.1 times, respectively, that of urea.
Scientific journal, English - ATTEMPTED SYNTHESES OF DIBENZOTETRAOXAFULVALENE
T ISHIDA; Y ISHIHARA; T YAMAGA; T NOGAMI
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 56, 1, 1968-1971, Mar. 1993, Peer-reviwed, We attempted to synthesize dibenzotetraoxafulvalene by several schemes in which carbene-like intermediates would be dimerized. The schemes involve the coupling reaction of 1,3-benzodioxolium cation by use of bases. The cation was planned to be obtained by two ways: hydride abstraction from 1,3-benzodioxole by use of triphenylmethyl cation and dealkoxylation form 2-methoxy- or 2-ethoxy-1,3-benzodioxole in the presence of a strong acid. Wurtz-type coupling reactions of 2,2-dichloro-1,3-benzodioxole were also investigated. Some products obtained in this study are expected to be precursors for further synthetic reactions to dibenzotetraoxafulvalene.
Scientific journal, English - SYNTHESIS OF MULTI-SULFUR TTF DERIVATIVES AND CONDUCTING ORGANIC SALTS
T NOGAMI; T ISHIDA; H YOSHIKAWA; M TANAKA; T NAITO; H KOBAYASHI; A KOBAYASHI
SYNTHETIC METALS, ELSEVIER SCIENCE SA LAUSANNE, 56, 1, 2039-2043, Mar. 1993, Peer-reviwed, Several BEDT-TTF salts were synthesized. BEDT-TTF3Br2 and BEDT-TTF-C(CN)3-CuCN were metallic down to 4.2 K. The crystal structure of the former salt was determined. New multi-sulfur TTF derivatives (OTHT, TOTT, and ETT) were synthesized, and their ion-radical salts were obtained by an electrochemical method. We also obtained new donor molecules containing six or seven sulfur atoms which were expected to give new conducting organic salts with two-dimensional electrical properties.
Scientific journal, English - INTRAMOLECULAR MAGNETIC INTERACTION OF TRANSITION-METAL IONS IN COMPLEXES CONTAINING PYRIMIDINE OR PYRAZINE AS A BRIDGING LIGAND
T ISHIDA; S MITSUBORI; T NOGAMI; H IWAMURA
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, GORDON BREACH SCI PUBL LTD, 232, 705-710, 1993, Peer-reviwed, The magnetic interactions between transition metal ions bridged with 4,6-pyrimidinedicarboxylate, 4,6-dipyridylpyrimidine, 2,3-pyrazinedicarboxylate, or 2,3-dipyridylpyrazine were studied. Several dinuclear complexes containing Cu2+, Ni2+, Co2+, or Mn2+ were synthesized and characterized. They were antiferromagnetically coupled in all cases.
Scientific journal, English - Addition Reactions of Benzyne, Dienes, Dichlorocarbene, and Oxygen to C60
M. Tsuda; T. Ishida; T. Nogami; S. Kurono; M. Ohashi
Fullerene Science and Technology, 1, 275-285, 1993, Peer-reviwed
Scientific journal, English - INTERMOLECULAR FERROMAGNETIC INTERACTION OF 4-(1-PYRENYLMETHYLENEAMINO)-2,2,6,6-TETRAMETHYLPIPERIDIN-1-OXYL
T ISHIDA; K TOMIOKA; T NOGAMI; H IWAMURA; K YAMAGUCHI; W MORI; Y SHIROTA
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 232, 99-102, 1993, Peer-reviwed, The magnetic properties of a microcrystalline sample of the title free radical were measured. This magnetic behavior can be interpreted in terms of ferromagnetic interaction inside chains or sheets accompanied by antiferromagnetic coupling between them. Other organic TEMPO derivatives containing donor or acceptor sites were synthesized.
Scientific journal, English - Intramolecular Magnetic Interaction of Transition Metal Ions in Complexes Containing Pyrimidine or Pyrazine as a Bridging Ligand
T. Ishida; S.-I. Mitsubori; T. Nogami; H. Iwamura
Molecular Crystals and Liquid Crystals, 233, 345-350, 1993, Peer-reviwed
International conference proceedings, English - INTRAMOLECULAR MAGNETIC COUPLING BETWEEN 2-NITRENE OR 2-NITROXIDE UNITS THROUGH 1,1-DIPHENYLETHYLENE CHROMOPHORES - ISOMERIC DINITRENES AND DINITROXIDES RELATED IN CONNECTIVITY TO TRIMETHYLENEMETHANE, TETRAMETHYLENEETHANE, AND PENTAMETHYLENEPROPANE
T MATSUMOTO; T ISHIDA; N KOGA; H IWAMURA
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 114, 25, 9952-9959, Dec. 1992, Peer-reviwed, Isomeric vinylidenebis(phenylnitrenes) (N) and 1,1-bis[ (N-oxy-tert-butylamino)phenyl]-2-methylpropenes (O) have been prepared, and their EPR fine structures and/or effective magnetic moments have been determined over a wide temperature range. The data were analyzed in terms of Bleaney-Bowers-type equations to give the energy gaps between the quintet and singlet states for N and the triplet and singlet states for 0. They were >>0 cm-1, -42.0 cm-1 (-502 J/mol, a negative value representing a singlet ground state), and -26.2 cm-1 (-313 J/mol), and 10.6 cm-1 (127 J/mol), -1.8 cm-1 (-22 J/mol), and -3.4 cm-1 (-41 J/mol) for p,p'-, m,p' and m,m'-dinitrenes N and dinitroxides O, respectively. A consistent reduction in the effective intramolecular exchange integrals Js between the two open-shell centers in the latter series is ascribed to the lower spin polarization on the phenyl rings of the dinitroxides relative to the dinitrenes. Whereas the ferro- and antiferromagnetic couplings in the p,p' and m,p'-topology are consistent not only with the Ovchinnikov's but also Borden-Davidson's rules, the antiferromagnetic interaction in the m,m'-substitution pattern is contradictory to the former and consistent with the latter theory. Since the p,p', m,p', and m,m' isomers are related to trimethylenemethane (4), tetramethyleneethane (5), and pentamethylenepropane (6), respectively, the results obtained in this work are consistent with the triplet ground state of 4. 5 and 6 are suggested to have ground singlet states. Radical centers X should be all at the para position for designing super-high-spin polyacetylenes 1 and polydiacetylenes 2.
Scientific journal, English - ADDITION-REACTION OF BENZYNE TO C60
M TSUDA; T ISHIDA; T NOGAMI; S KURONO; M OHASHI
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 12, 2333-2334, Dec. 1992, Peer-reviwed, Benzyne generated by the reaction of 2-aminobenzoic acid and pentyl nitrite in a refluxing benzene was found to add to C60 in good yield, The reaction products were separated by HPLC to give C60(C6H4), C60(C6H4)2, C60(C6H4)3, and C60(C6H4)4, which were confirmed by mass spectra. H-1 NMR spectrum of C60(C6H4) is consistent with the structure of mono-addition product, whereas those of C60(C6H4)2, C60(C6H4)3, and C60(C6H4)4 indicate that they consist of the corresponding mixtures of isomers.
Scientific journal, English - APPROACHES FROM HIGH-SPIN ORGANIC-MOLECULES TO ORGANIC FERROMAGNETS
T ISHIDA; K INOUE; N KOGA; N NAKAMURA; H IWAMURA
ELECTRICAL, OPTICAL, AND MAGNETIC PROPERTIES OF ORGANIC SOLID STATE MATERIALS, MATERIALS RESEARCH SOC, 247, 407-416, 1992, Peer-reviwed
International conference proceedings, English - BIS[3-TERT-BUTYL-5-(N-OXY-TERT-BUTYLAMINO)PHENYL] NITROXIDE IN A QUARTET GROUND-STATE - A PROTOTYPE FOR PERSISTENT HIGH-SPIN POLY[ (OXYIMINO)-1,3-PHENYLENES]
T ISHIDA; H IWAMURA
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 113, 11, 4238-4241, May 1991, Peer-reviwed, The title trinitroxide 4 was synthesized via the bis[m-(hydroxyamino)phenyl] nitroxides 9 and 10. The ESR spectra obtained in a toluene glass at 4.2 K was consistent with 4 in a quartet state with the zfs parameter \D\/hv of 0.0087 cm-1. The quartet state was shown to be the ground state by the magnetic measurement of its microcrystalline sample on a Faraday balance. The maximum of the effective moment was 3.53-mu-B at ca. 140 K. The Weiss constant and the energy gap between the lowest excited doublet and the ground quartet states were estimated to be -19 and +240 K, repsectively.
Scientific journal, English - SYNTHESES AND MAGNETIC-PROPERTIES OF POLY(PHENYLACETYLENES) CARRYING A (1-OXIDO-3-OXY-4,4,5,5-TETRAMETHYL-2-IMIDAZOLIN-2-YL) GROUP AT THE META OR PARA POSITION OF THE PHENYL RING
A FUJII; T ISHIDA; N KOGA; H IWAMURA
MACROMOLECULES, AMER CHEMICAL SOC, 24, 5, 1077-1082, Mar. 1991, Peer-reviwed, 2-(m-Ethynyl- and p-ethynylphenyl)-4,4,5,5-tetramethyl-2-imidazoline 1-oxide 3-oxyls (m-3 and p-3) were prepared and allowed to polymerize in the presence of Rh(COD)(NH3)Cl in ethanol and ethanol/benzene, respectively, at room temperature. The greenish homopolymer (m-2) from the m-isomer was soluble in ordinary organic solvents and had an approximate molecular weight (vs standard polystyrene by GPC) on the order of 150 000. The dark blue homopolymer (p-2) from the p-isomer was insoluble. ESR spectra of 2 showed single lines with the width of 0.7-0.8 mT. The nitronyl nitroxides in the side chains were estimated from elemental analyses, ESR signal intensities, and Curie constants to be more than 95% intact. The magnetic properties have been determined by a Faraday balance in the temperature range 2-300 K and magnetic field range 0-7 T. The 1/chi vs temperature plots gave straight lines characteristic of paramagnetic species with very weak antiferromagnetic coupling (theta = -1.7 and -1.5 K for m-2 and p-2, respectively). The magnetization vs magnetic field strength data on the two isomeric samples at 1.8 K deviated slightly downward from the Brillouin functions with S = 1/2, suggesting again the presence of antiferromagnetic coupling between the S = 1/2 spins. The expected ferromagnetic coupling among the radical centers in the side chains through the conjugated main chain was concluded not to be operative in these polymers.
Scientific journal, English - AN IMPROVED SYNTHESIS OF POLY(META-ANILINE) AND THE MAGNETIC-PROPERTIES OF ITS HCL SALT
T ISHIDA; H IWAMURA
CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 2, 317-318, Feb. 1991, Peer-reviwed, An analytically satisfactory sample of poly(m-aniline) was obtained from m-bromoaniline in the presence of a copper-based catalyst. The magnetic susceptibility of the HCl salt followed a Curie-Weiss law and the spin concentration was determined to be 2.6 x 10(19) spins/g.
Scientific journal, English - THIOALDEHYDE ANION RADICALS
D CASARINI; L LUNAZZI; G PLACUCCI; T ISHIDA; A ISHII; R OKAZAKI
JOURNAL OF ORGANIC CHEMISTRY, AMER CHEMICAL SOC, 53, 7, 1582-1584, Apr. 1988, Peer-reviwed
Scientific journal, English - UNUSUALLY READY CLEAVAGE OF AN S-C-ALPHA BOND IN STERICALLY CROWDED SULFOXIDES
R OKAZAKI; T ISHIDA; N INAMOTO
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 1, 40-41, Jan. 1988, Peer-reviwed
Scientific journal, English - Biradical pincers involving two phenylene, biphenylene or terphenylene arms: Evidence for approach of two terminal nitroxides
R. Uesugi; R. Takano; T. Ishida
Last, Tetrahedron, 1900, Peer-reviwed
Scientific journal, Japanese
MISC
- 分子磁性研究の展開と深化：4f-3d単分子磁石の周辺研究を一例として
石田尚行
Oct. 2012, 電子スピンサイエンス（表紙）, 10 (Autumn), 94-99, Japanese, Introduction other - 21aCD-5 Trends in Exchange Coupling in Re-Radical Complex
Nojiri H.; Tanaka T.; Baker M.; Ishida T.
The Physical Society of Japan (JPS), 24 Aug. 2012, Meeting abstracts of the Physical Society of Japan, 67, 2, 442-442, Japanese, 1342-8349, 110009600075, AA11439205 - Evaluation of Exchange Interaction of Rare-Earth Nanomagnets
T. Ishida; H. Nojiri; S. Yoshii; G. Tanaka
22 Jun. 2011, NanotechJapan Bulletin, 4, 3, 1-10, English, Introduction commerce magazine - 希土類ナノ磁石の交換相互作用評価
石田尚行; 野尻浩之; 吉居俊輔; 田中 豪
Dec. 2010, NanotechJapan Bulletin（Web マガジン：フォーカス26）, 第14回, nanonet.nims.go.jp/magazine/, Japanese, Introduction other - 27aQJ-11 Exchange coupling and magnetism of RE-3d hetero-metallic magnetic molecule
Nojiri H.; Hayashi M.; Tanaka G.; Yoshii S.; Gomella A.; Ishida T.; Okazawa K.
The Physical Society of Japan (JPS), 18 Aug. 2009, Meeting abstracts of the Physical Society of Japan, 64, 2, 368-368, Japanese, 1342-8349, 110007497314, AA11439205 - 20aQH-7 Magnetism and Exchange Interaction in RE-3d Heterometallic Molecular Magnet
Nojiri H.; Yoshii S.; Ishida T.; Okazawa A.
The Physical Society of Japan (JPS), 25 Aug. 2008, Meeting abstracts of the Physical Society of Japan, 63, 2, 359-359, Japanese, 1342-8349, 110006983785, AA11439205 - ET and TTF Salts with Lanthanide Complex Ion Showing Frequency Dependent ac Magnetic Susceptibility
UEKI Sohei; NOGAMI Takashi; ISHIDA Takayuki; TAMURA Masafumi
2006, Mol. Cryst. Liq. Cryst., 455, 129-134, 1058-725X, 80018853843 - 特殊文字が正しく表示されていませんので、http://ttf.pc.uec.ac.jp/www.page/paperlist_TI.pdf もご参照下さい。
T. Ishida
2000, 9999, 1-9999, English, Peer-reviwed, Others - CRYSTAL STRUCTURES OF COPPER COMPLEXES SHOWING FERROMAGNETIC INTERACTION.
M. Yasui; Y. Ishikawa; T. Nogami; T. Ishida; F. Iwasaki
INT UNION CRYSTALLOGRAPHY, 1996, ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 52, C451-C451, English, Summary international conference, 2053-2733, WOS:000410483400202
Books and other publications
- Synthesis and Applications of New Spin Crossover Compounds (Crystals Special Issue )
A. Ondo; T. Ishida
Scholarly book, English, Contributor, Cobalt(II) Terpyridin-4'-yl Nitroxide Complex as an Exchange-Coupled Spin-Crossover Material, MDPI, Sep. 2019 - Spin-Crossover Complexes (Inorganics Special Issue )
A. Kimura; T. Ishida
Scholarly book, English, Contributor, Pybox-Iron(II) Spin-Crossover Complexes with Substituent Effects from the 4-Position of the Pyridine Ring (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine), MDPI, 28 May 2018, 9783038428251 - CSJカレントレビュー16「スピン化学が拓く分子磁性の新展開：設計から機能化まで」
石田尚行
Scholarly book, Japanese, Contributor, f-d and f-p heterospin single-molecule magnets, 化学同人, 01 Aug. 2014, 9784759813760 - Multifunctional Conducting Molecular Materials
M. Suzuki; T. Fujii; T. Nogami; T. Hirano; T. Ishida
Scholarly book, English, Contributor, Electron Donors from Natural Products: Donating and Ligating Abilities and Charge-Transfer Complex Formation of Imidazo[1,2-a]pyrazin-3(7H)-ones, RSC Publishing, 2007, 0854044965 - Molecular Magnetism - New Magnetic Materials
T. Nogami; T. Ishida
Scholarly book, English, Contributor, Chap. 5.1, Molecular Design and Synthesis for Organic Molecular Magnetism - Novel Ferromagnetic TEMPO Radical Crystals, Kodansha-Gordon and Breach Science Publishers, 2000, 9056993070 - Recent Research Development of Pure and Applied Chemistry Volume 1
T. Ishida; T. Nogami
Scholarly book, English, Contributor, Pyrimidine-Bridged Transition Metal Complexes as a Polymer Approach to Molecule-Based Ferromagnets, Transworld Research Network, 1998, 8186846131 - Advanced Materials '93 1st Edition: Ceramics, Powders, Corrosion and Advanced Processing
T. Nogami; M. Tsuda; T. Ishida; S. Kurono; M. Ohashi
Scholarly book, English, Contributor, Synthesis and Characterization of C60 Adducts with Benzyne, Dichlorocarbene, Dienes, and Oxygen, Elsevier, 1994 - New Functionality Materials, Vol. C, Synthetic Process and Control of Functionality Materials
T. Nogami; T. Ishida
Scholarly book, English, Contributor, Magnetic Properties and Nonlinear Optical Properties of Organic Materials, Elsevier Science, 1993, 044481616X
Lectures, oral presentations, etc.
- pH effect on hydrothermal synthesis of the copper organodiphosphonate polymers: Investigation of luminescence and magnetic properties
B. Ay; T. Ishida
Oral presentation, English, The 103rd CSJ Annual Meeting, The 103rd CSJ Annual Meeting organizing comittee, Noda, Domestic conference
22 Mar. 2023 - Photoluminescence Properties of a Three-Dimensional Coordination Polymer from Rare Earth Ion and Small Ligands
R. Takano; B. Ay; T. Ishida
Oral presentation, English, The 103rd CSJ Annual Meeting, The 103rd CSJ Annual Meeting organizing comittee, Noda, Domestic conference
22 Mar. 2023 - Chains and Macrocycles of Heavy Lanthanide Ions Bridged with a Triplet Biradical
T. Ishida; S. Ito; S. Ueno; S.-i. Hatanaka
Oral presentation, English, 44th International Conference on Coordination Chemistry, ICCC organizing comittee, Rimini, Italy, International conference
28 Aug. 2022 - Key to Tune Crystal Field for Multistep Spin Crossover in Dinuclear Iron(II) Helicates with Diimine Ligands
R. Takano; T. Ishida
Oral presentation, English, 44th International Conference on Coordination Chemistry, ICCC organizing comittee, Rimini, Italy, International conference
28 Aug. 2022 - 4f-2pヘテロスピン系ナノ磁石と その関連材料科学
石田尚行
Invited oral presentation, Japanese, 新化学技術推進協会 先端化学・材料技術部会 新素材分科会, Invited, 公益社団法人 新化学技術推進協会, オンライン, Domestic conference
12 Mar. 2021 - 4f-2pヘテロスピン系ナノ磁石とその関連材料科学
石田尚行
Invited oral presentation, Japanese, 新化学技術推進協会 先端化学・材料技術部会 新素材分科会, Invited, 公益社団法人 新化学技術推進協会, オンライン, Domestic conference
12 Mar. 2021 - 希土類イオンを使った分子性磁性材料
石田尚行
Invited oral presentation, Japanese, 近畿化学協会エレクトロニクス部会研究会「希少金属を取り巻く基礎研究と国際マーケットの現況」, Invited, 一般社団法人 近畿化学協会, オンライン, Domestic conference
03 Dec. 2020 - 希土類錯化合物のスピン科学と分子磁性材料
石田尚行
Invited oral presentation, Japanese, 近畿化学協会エレクトロニクス部会研究会「希少金属を取り巻く基礎研究と国際マーケットの現況」, Invited, 一般社団法人 近畿化学協会, オンライン, Domestic conference
03 Dec. 2020 - Synthesis and Magnetic Properties of Coordination Compounds with π-Extended Multi-Radical-Substituted Ligands
Y. Gokan; T. Kanetomo; T. Ishida
Poster presentation, English, The Irago Conference 2019, UEC Tokyo, International conference
29 Oct. 2019 - Systematic Study on Iron(II) Spin Crossover Complexes Chelated with 2,6-Bis(1-pyrazolyl)pyridine Ligands Carrying Alkyl Groups
S. Soda; T. Ishida
Poster presentation, English, The Irago Conference 2019, UEC Tokyo, International conference
29 Oct. 2019 - 国内学会（年会、研究会）一般発表については、http://ttf.pc.uec.ac.jp/www.page/conflist_TI.pdf をご参照下さい。
石田尚行ら
Others, Japanese
2019 - Structures and Magnetic Properties of Lanthanide Complexes Involving Ground Triplet Bisnitroxide Radicals
H. Sekine; T. Ishida
Oral presentation, English, The Irago Conference 2018, Irago Conf Committee, Shinjuku, Tokyo, International conference
01 Nov. 2018 - Biphenyl-Hinged Bisnitroxide Biradicals toward Intramolecular Para- and Diamagnetic Switching
M. Arai; T. Ishida
Oral presentation, English, The Irago Conference 2018, Irago Conf Committee, Shinjuku, Tokyo, International conference
01 Nov. 2018 - Synthetic Investigation for Spiro-Junctioned Biradical Compounds
K. Ichihashi; T. Ishida
Oral presentation, English, The Irago Conference 2018, Irago Conf Committee, Shinjuku, Tokyo, International conference
01 Nov. 2018 - Gradual Structure Transition and Novel Spin Transition/Crossover
T. Ishida
Invited oral presentation, English, 2nd RIKEN Symposium International Workshop on Organic Molecular Systems/4th International Conference on Functional Materials Science, Invited, RIKEN & FMS-net, Bali, Indonesia, International conference
Nov. 2018 - Moving Molecules in Crystalline Solids: Gradual Structure Transition and Spin Transition/Crossover
T. Ishida
Invited oral presentation, English, International Conference on Condensed Matters and Advanced Materials (IC2MAM 2018), IC2MAM, Malang, Indonesia, International conference
05 Sep. 2018 - Magneto-Structural Relationship on Metal Complexes Using Dual Radical Chelate Ligand Showing Ground Triplet State
A. Okazawa; T. Ishida; N. Kojima
Oral presentation, English, The 43th International Conference on Coordination Chemistry, ICCC2018, Sendai, International conference
30 Jul. 2018 - Biradical-Bridged Lanthanide Complexes: Synthesis, Crystal Structures, and Physical Properties
T. Kanetomo; S. Yoshikado; K. Makimura; T. Ishida; M. Enomoto
Oral presentation, English, The 43th International Conference on Coordination Chemistry, ICCC2018, Sendai, International conference
30 Jul. 2018 - Unexpected Complexes from meta-Phenylene Bis(tert-butyl Nitroxides) and Gadolinium(III) 1,1,1,5,5,5-Hexafluoropentane-2,4-dionate
H. Sekine; T. Ishida
Oral presentation, English, The Irago Conference 2017, UEC-Tokyo, Chofu, Tokyo, International conference
Nov. 2017 - Substituent Effect in Spin-Crossover Behavior of Pybox-iron(II) Complexes (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine)
A. Kimura; T. Ishida
Oral presentation, English, The Irago Conference 2017, UEC-Tokyo, Chofu, Tokyo, International conference
Nov. 2017 - Sonochemical Synthesis of Magnetic Nanoparticles
S. Uchiyama; H. Miyashita; T. Ishida; S.-i. Hatanaka
Oral presentation, English, The Irago Conference 2017, UEC-Tokyo, Chofu, Tokyo, International conference
Nov. 2017 - Molecular Nanomagnets Consisting of Exchange-Coupled Heavy Rare-Earth Metal Ions and Nitroxide Radicals
T. Kanetomo; T. Nakamura; R. Murakami; T. Ishida
Oral presentation, English, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth, UEC, Chofu, Tokyo, International conference
Oct. 2017 - Ground Triplet Spirobiacridine-N,N’-dioxyls: Preparation, Structures, and Magnetic Properties
K. Ichihashi; T. Kanetomo; T. Ishida
Oral presentation, English, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth, UEC, Chofu, Tokyo, International conference
Oct. 2017 - Nanomagnets of Lanthanide Complexes Using 2,2,6,6-Tetramethylpiperidine 1-Oxyl Ligands
N. Koizumi; T. Ishida
Oral presentation, English, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth, UEC, Chofu, Tokyo, International conference
Oct. 2017 - Do Organic Free Radicals Dream of Future Magnets?
T. Ishida; N. Koizumi; H. Sekine
Oral presentation, English, RIKEN Symposium International Workshop on Organic Molecular Systems, RIKEN, Penang, Malaysia, International conference
Aug. 2017 - 重希土類とニトロキシドラジカルからなる単分子磁石
石田尚行; 小泉直樹; 中村健志; 村上里奈; 金友拓哉
Invited oral presentation, Japanese, 電気通信大学ナノトライボロジー研究センター開設シンポジウム, 電気通信大学ナノトライボロジー研究センター, 調布市, Domestic conference
08 Mar. 2017 - Exchange-Coupled Heavy-Lanthanoid and Nitroxide Molecular Magnets
T. Kanetomo; T. Nakamura; R. Murakami; T. Ishida
Invited oral presentation, English, Supramolecular Science-Based Organic Materials and Devices - 10th High-tech Research Center International Symposium, Invited, Toho University, Narashino, Japan, International conference
10 Dec. 2016 - Spin-Parity Behavior in the Exchange-Coupled Lanthanoid-Nitroxide Molecular Magnets
T. Ishida
Invited oral presentation, English, The International Conference on Advanced Materials Science and Technology, Indonesia (ICAMST 2016), Invited, ICAMST organizing comittee, Malang, Indonesia, International conference
27 Sep. 2016 - Chemical Trend on the Lanthanide-Radical Exchange Coupling
T. Ishida; T. Nakamura; T. Kihara; H. Nojiri
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Ferromagnetically Coupled Lanthanoid-Radical Complexes Showing Slow Reversal of Magnetization
T. Kanetomo; T. Yoshitake; H. Nojiri; T. Ishida
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Structure and Magnetic Properties of Copper Dinuclear Spiro-Complexes Involving Tetraiminoneopentane
A. Kimura; T. Ishida
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Structure and Magnetic Properties of Bisnitroxide Pincer Compounds with a Spacing-Control Hinge
N. Koizumi; T. Ishida
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Study on Imidazolate-Bridged Divalent 3d Metal Ion Complexes Capped with Tris(1-pyrazolyl)methane
T. Kogane; M. Yamazaki; T. Kanetomo; T. Ishida
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Syntheses, Crystal Structures, and Magnetic Properties of Copper(II) Complexes with Bischelate and High-Spin Biradical Ligand
A. Okazawa; T. Ishida; K. Ogawa; N. Kojima
Oral presentation, English, The 15th International Conference on Molecule-based Magnets (ICMM 2016), ICMM, Sendai, International conference
Sep. 2016 - Molecular Design for the Strongest Magnetic Couplings in Gadolinium-Nitroxide Systems
T. Ishida
Invited oral presentation, English, Osaka City University International Conference (OCUIC 2016), Invited, Osaka City University, International conference
31 Aug. 2016 - Structures and Magnetic Properties of Transition-Metal Complexes Involving Bipyridinyl Nitroxide Radicals
A. Ondo; T. Ishida
Oral presentation, English, The Irago Conference 2016, UEC & TUT, Chofu, International conference
2016 - Development of Biradical Ligands toward [2×2] Molecular Grids
K. Ichihashi; S. Ohba; T. Ishida
Oral presentation, English, The Irago Conference 2016, UEC & TUT, Chofu, International conference
2016 - Synthesis and Magnetic Properties of Transition Metal Complexes with Multichelating and High-Spin Radical Ligands
A. Okazawa; T. Ishida; N. Kojima; K. Ogawa
Poster presentation, English, Pacifichem2015, Hawaii, USA, International conference
Dec. 2015 - Strongest Ferromagnetic Exchange Coupling in Gadolinium(III)-Nitroxide Coordination Compounds
T. Kanetomo; T. Yoshitake; T. Ishida
Poster presentation, English, Pacifichem2015, Hawaii, USA, International conference
Dec. 2015 - Study on Gd-O-N Angular Dependence of Magnetic Exchange Interaction in Gadolinium(III) Complexes Having Aliphatic Nitroxide Radicals
T. Nakamura; T. Ishida
Poster presentation, English, The Irago Conference 2015, International conference
Oct. 2015 - Pyridine-2,6-diyl Dinitroxides as Room-Temperature Triplet Biradicals
H. Kawakami; A. Tonegawa; T. Ishida
Poster presentation, English, The Irago Conference 2015, International conference
Oct. 2015 - Luminescent Single-Ion Magnets from Lanthanoid(III) Complexes with Monodentate Ketone Ligands
T. Kanetomo; T. Ishida
Poster presentation, English, The Irago Conference 2015, International conference
Oct. 2015 - ヘテロスピン単分子磁石の設計、開発、計測
石田尚行
Invited oral presentation, Japanese, 日本物理学会第70回年次大会, Invited, Domestic conference
22 Mar. 2015 - The Relationship Between Torsion and Anisotropic Exchange Coupling in a Tb(III)-Radical Complex
M. L. Baker; T. Tanaka; S. Kawamura-Ohira; K. Nakajima; T. Ishida; H. Nojiri
Oral presentation, English, APS March Meeting, APS, San Antonio, USA, International conference
Mar. 2015 - Evaluation of Dysprosium(III)-Copper(II) Exchange Coupling Parameters and Relation with the Bridging Geometry
Y. Ida; T. Ishida; S. Ghosh; A. Ghosh; H. Nojiri
Oral presentation, English, Asia-Pacific EPR/ESR Symposium/International EPR (ESR) Society Symposium/the 53th SEST Annual Meeting (APES2014-IES-SEST2014), Nara, International conference
16 Nov. 2014 - Study on Magnetic Anisotropy and Slow Magnetization Relaxation of a Gadolinium(III)-Radical Complex
T. Kanetomo; H. Nojiri; T. Ishida
Oral presentation, English, Asia-Pacific EPR/ESR Symposium/International EPR (ESR) Society Symposium/the 53th SEST Annual Meeting (APES2014-IES-SEST2014), Nara, International conference
15 Nov. 2014 - Exchange Couplings in Mono-, Di-, and Polymeric [DyCu2] Compounds
Y. Ida; A. Ghosh; T. Ishida
Oral presentation, English, 5th Topical Meeting on Spins in Organic Semiconductors (SpinOS 2014), Himeji, International conference
14 Oct. 2014 - Strong exchange couplings in lanthanide complexes with aliphatic nitroxide radicals
T. Nakamura; R. Murakami; T. Ishida
Oral presentation, English, The 14th International Conference on Molecule-Based Magnets (ICMM 2014), Saint Petersburg, Russia, International conference
08 Jul. 2014 - Structures and Magnetic Properties of Two Phases from Imidazolate-Bridged Copper(II) Pyrazolylborate Complexes
T. Kogane; T. Kanetomo; H. Muroyama; T. Ishida
Oral presentation, English, The 14th International Conference on Molecule-Based Magnets (ICMM 2014), Saint Petersburg, Russia, International conference
08 Jul. 2014 - Exchange Interactions within 4f-2p Coupled Electron Systems
M. L. Baker; T. Tanaka; G. G. Simeoni; K. Nakajima; Seiko Ohira-Kawamura; T. Ishida; H. Nojiri
Oral presentation, English, The 14th International Conference on Molecule-Based Magnets (ICMM 2014), Saint Petersburg, Russia, International conference
08 Jul. 2014 - Spin-Crossover Thermal Hysteresis and Light-Induced Effect on Iron(II) Complexes with Tripodal Tris(2-pyridyl)methanol
M. Yamasaki; T. Ishida
Oral presentation, English, The 14th International Conference on Molecule-Based Magnets (ICMM 2014), Saint Petersburg, Russia, International conference
07 Jul. 2014 - Single-Molecule Magnets Involving Strong Exchange in Lanthanoid Complexes with 2,2’-Bipyridin-6-yl tert-Butyl Nitroxide
T. Kanetomo; S. Yoshii; H. Nojiri; T. Ishida
Oral presentation, English, The 14th International Conference on Molecule-Based Magnets (ICMM 2014), Saint Petersburg, Russia, International conference
06 Jul. 2014 - Preparation and characterization of [Gd(hfac)3(DTBN)(H2O)] (DTBN = di-t-butyl nitroxide). Ferromagnetic Gd3+-Gd3+ super-superexchange
T. Kanetomo; T. Ishida
Invited oral presentation, English, The 7th Japanese-Russian Workshop on Open Shell Compounds and Molecular Spin Devices, Invited, Japanese-Russian Workshop Organizing Committee, Awaji Island, International conference
Nov. 2013 - Exchange Coupling of Rare-earth-Radical Hetero-Spin Magnetic Clusters-ESR and Neutron Scattering Study
T. Tanaka; M. Baker; H. Nojiri; T. Ishida
Oral presentation, English, The 12th Asia Pacific Physics Conference
Jul. 2013 - Relatively Strong Exchange Coupling in Lanthanoid-Nitroxide Heterospin Compounds
T. Kanetomo; R. Murakami; T. Ishida
Oral presentation, English, The 1st Awaji International Workshop on Electron Spin Science & Technology: Biological and Materials Science Oriented Applications
Jun. 2013 - Entropy-Driven Three-Centered Spin-Crossover-Like Behavior in a Nickel(II) Bis(nitroxide) Complex
Y. Homma; T. Ishida
Invited oral presentation, English, The 1st Awaji International Workshop on Electron Spin Science & Technology: Biological and Materials Science Oriented Applications, The 1st Awaji International Workshop on Electron Spin Science & Technology: Biological and Materials Science Oriented Applications, Awaji, International conference
Jun. 2013 - Determination of Crystal-Field Energy Levels and Temperature Dependence of Magnetic Susceptibility for Dy3+ in [Dy2Pd] Heterometallic Complex
M. Karbowiak; C. Rudowicz; T. Ishida
Oral presentation, English, International Conference on Rare Earth Materials
Apr. 2013 - 3d-2p and 4f-2p Heterospin Molecules
T. Ishida
Invited oral presentation, English, Workshop on Molecular Magnets 2013, Workshop on Molecular Magnets 2013, Sendai, International conference
Feb. 2013 - Spin-Transition-Like Behavior in a Novel Heterospin Triad: Bis(nitroxide)-Chelated Nickel(II) Chloride
Y. Homma; T. Ishida
Oral presentation, English, International Symposium on Materials Science Opened by Molecular Degrees of Freedom
Dec. 2012 - Magnetic and EPR Studies of S = 3 Nickel(II) Triangular Complexes Having μ3-Hydroxo- and μ3-Halogeno-Bridges
Y. Ida; K. Miyamoto; E. Horn; M. L. Baker; H. Nojiri; T. Ishida
Oral presentation, English, The 13th International Conference on Molecule-Based Magnets
Oct. 2012 - Magnetic and EPR Studies on Radical-Lanthanide-Based Single-Molecule Magnets
T. Ishida; R. Murakami; T. Kanetomo; M. L. Baker; S. Yoshii; H. Nojiri
Oral presentation, English, The 13th International Conference on Molecule-Based Magnets
Oct. 2012 - Crystal Structures and Magnetic Properties of Two-dimensional Copper(II) Complexes Bridged with Pyrazine-2-carboxamide
M. Yoshida; T. Shimada; T. Ishida; T. Kogane
Oral presentation, English, The 13th International Conference on Molecule-Based Magnets
Oct. 2012 - Chemical Modification of 4f-3d Heterometallic [Ln2Ni]-type Single-Molecule Magnets
A. Okazawa; T. Ishida; H. Nojiri; S. Yoshii; N. Kojima
Oral presentation, English, The 13th International Conference on Molecule-Based Magnets
Oct. 2012 - A Novel Fluoride-bridged Ni(II) Trimeric Complex Having N-Alkylethylenediamine
K. Miyamoto; Y. Ishikawa; E. Horn; Y. Ida; T. Ishida
Oral presentation, English, The 40th International Conference on Coordination Chemistry
Sep. 2012 - Synthesis, Properties and Structure of Nickel(II) Tri-mer and Nickel(II) Mono-mer Complexes
Y. Ishikawa; K. Miyamoto; E. Horn; Y. Ida; T. Ishida
Oral presentation, English, The 40th International Conference on Coordination Chemistry
Sep. 2012 - 4f-3dヘテロ金属錯体の磁気的相互作用
石田尚行
Invited oral presentation, Japanese, 日本物理学会秋季大会, 日本物理学会, Domestic conference
Sep. 2012 - Heterospin 4f-3d and 4f-2p Magnets
T. Ishida; R. Murakami; T. Kanetomo; T. Shimada; S. Yoshii; H. Nojiri
Invited oral presentation, English, The Fujihara Seminar: Frontier and Perspectives in Molecule-Based Quantum Magnets, The Fujihara Seminar, Sendai, International conference
May 2012 - Hetero-spin 4f-3d and 4f-2p magnets
T. Ishida
Oral presentation, English, Frontier and Perspectives in Molecule-Based Quantum Magnets
May 2012 - Synthesis and Magnetic Study of Triplet Biradicals toward Materials Showing Thermally Induced Magnetism
T. Konno; S. Hirose; T. Ishida
Oral presentation, English, Open-shell Organic Molecules - Synthesis and Electronic Structure Freedom
Oct. 2011 - Ferromagnetic Coupling in Hydro Nitronyl Nitroxide-Gd(III) and Antiferromagnetic Coupling in 2-Pyridyl Nitroxide-Gd(III) Complexes
R. Murakami; N. Ikegaya; T. Kanetomo; T. Ishida
Oral presentation, English, Open-shell Organic Molecules - Synthesis and Electronic Structure Freedom
Oct. 2011 - Magnetic Exchange Couplings Showing a Chemical Trend in 4f-3d Heterometallic Complexes
T. Ishida
Invited oral presentation, English, Workshop on Development of Functionalized Molecule-based Magnetic Materials, International Collaboration Center of Institute for Materials Reserch, Tohoku Univ., Sendai, International conference
Sep. 2011 - Long-Range Order and Motion of Magnetic Domain Wall in Quasi One-Dimensional Co-Radical Coordination Polymer
T. Ishida
Invited oral presentation, English, The 3rd International Advisory Committee for the RIKEN-RAL Muon Facility, RIKEN-RAL, Wako, International conference
Feb. 2011 - Supramolecular Chemistry Using Nitroxide Biradical Polyethers. Structural, Magnetic, and ESR Studies of Their Complex Formation with Metal Ions
S. Osada; T. Ishida
Oral presentation, English, The 2010 International Chemical Congress of Pacific Basin Societies
Dec. 2010 - Determination of Exchange Couplings in Dinuclear 4f-3d Heterometallic Nano-Sized Magnets
T. Ishida; R. Watanabe; K. Fujiwara; A. Okazawa; G. Tanaka; S. Yoshii; H. Nojiri
Oral presentation, English, The 2010 International Chemical Congress of Pacific Basin Societies
Dec. 2010 - Spin-Transition-Like Behavior of Radical Chelate Complexes Accompanied by Twisted Deformation around Copper(II)-Nitroxide Coordination Bond
A. Okazawa; T. Ishida
Oral presentation, English, The 2010 International Chemical Congress of Pacific Basin Societies
Dec. 2010 - Exchange Couplings in One-dimentionally Arrayed 4f-3d Heterometallic [Ln2Cu2]n Compounds
A. Okazawa; K. Fujiwara; R. Watanabe; S. Yoshii; H. Nojiri; T. Ishida
Oral presentation, English, The 12th International Conference on Molecule-based magnets
Oct. 2010 - Ferromagnetic Oxovanadium(IV) Complexes Chelated with Tetrahalosalen Ligands
K. Fujiwara; T. Ishida
Oral presentation, English, The 12th International Conference on Molecule-based magnets
Oct. 2010 - 2,2’-Bipyridine-6,6’-diyl Bisnitroxide as A Paramagnetic Host
K. Koide; T. Ishida
Oral presentation, English, The 12th International Conference on Molecule-based magnets
Oct. 2010 - Single-Molecule Magnet Behavior Enhanced by Magnetic Coupling between 4f-3d Spins
A. Okazawa; H. Nojiri; T. Ishida; N. Kojima
Oral presentation, English, The 12th International Conference on Molecule-based magnets
Oct. 2010 - Attempted Synthesis of Axial-Equatorial Pyrazine-Bridged Copper(II) Complexes toward Homometallic Ferromagnetic Compounds
R. Watanabe; T. Shimada; N. Koyama; T. Ishida; T. Kogane
Oral presentation, English, The 12th International Conference on Molecule-based magnets
Oct. 2010 - Spin dynamics of cobalt-radical one-dimensional magnets
T. Ishida; N. Ishii; Y. Okamura; Y. Ishii; I. Watanabe
Oral presentation, English, ISSP-MDF Joint International Workshop Spin-Related Phenomena in Organic Materials
Jul. 2010 - The Most Coercive Magnets from Molecule-Based Cobalt(II)-Radical Chain Compounds
T. Ishida; Y. Okamura; N. Ishii; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 2010 - Determination of Exchange Interaction in Lanthanide Nano-Magnets
手老省三; 石田尚行; 野尻浩之
Poster presentation, Japanese, nano tech 2010（国際ナノテクノロジー総合展・技術会議）, Invited, nano tech 実行委員会, 東京ビッグサイト, Domestic conference
17 Feb. 2010 - The Hardest Magnets from Alternating Cobalt(II)-Radical Heterospins
T. Ishida; Y. Okamura; I. Watanabe
Invited oral presentation, English, The 3rd Japanese-Russian Workshop on Open Shell Compounds and Molecular Spin Devices, Japanese-Russian Workshop Organizing Committee, Awaji, International conference
Nov. 2009 - 希土類ナノ磁石の交換相互作用評価
石田尚行; 吉居俊輔; 野尻浩之
Invited oral presentation, Japanese, 文部科学省先端研究施設共用イノベーション創出事業 ナノテクノロジー・ネットワーク H21年度成果報告会, 文部科学省先端研究施設共用イノベーション創出事業 ナノテクノロジー・ネットワーク, Domestic conference
Nov. 2009 - Muon-Spin Rotation and Relaxation on the One-Dimensional Coordination Polymer Magnet [Co(hfac)2•HNN] (HNN = hydro nitronyl nitroxide)
T. Ishida; Y. Okamura; Y. Ishii; I. Watanabe
Oral presentation, English, RIKEN Accelerator Progress Report
2009 - Muon-Spin Rotation and Relaxation on the One-Dimensional Coordination Polymer Magnet [Co(hfac)2•HNN] (HNN = hydro nitronyl nitroxide)
T. Ishida; Y. Okamura; Y. Ishii; I. Watanabe
Oral presentation, English, RIKEN-RAL Muon Facility Report
2009 - Muon Spin Rotation and Relaxation on the One-Dimensional Cobalt(II)-Radical Coordination Polymer Magnet
T. Ishida; Y. Okamura; I. Watanabe
Oral presentation, English, RIKEN Accelerator Progress Report 2008
2009 - Muon-Spin Rotation and Relaxation on the One-Dimensional Coordination Polymer Magnet [Co(hfac)2•HNN] (HNN = hydro nitronyl nitroxide)
T. Ishida; Y. Okamura; Y. Ishii; I. Watanabe
Oral presentation, English, RIKEN Accelerator Progress Report
2009 - Muon-Spin Rotation and Relaxation on the One-Dimensional Coordination Polymer Magnet [Co(hfac)2•HNN] (HNN = hydro nitronyl nitroxide)
T. Ishida; Y. Okamura; Y. Ishii; I. Watanabe
Oral presentation, English, RIKEN-RAL Muon Facility Report
2009 - Ferromagnetic Coupling of Copper(II) and Nickel(II) Complexes with a Cyclam-based Paramagnetic Host
K. Igarashi; T. Nogami; T. Ishida
Oral presentation, English, 11th International Conference on Molecule-based Magnets
Sep. 2008 - Strong Ferromagnetic Exchange Couplings in Copper(II) and Nickel(II) Complexes Chelated with tert-Butyl 5-Methoxyphenyl-2-Pyridyl Nitroxide. A Magneto-Structure Relationship
A. Okazawa; T. Nogami; T. Ishida
Oral presentation, English, 11th International Conference on Molecule-based Magnets
Sep. 2008 - Magnetic Properties and Exchange Couplings of One-Dimensionally Arrayed 4f-3d Heterometallic [Ln2Cu2]n Comounds
A. Okazawa; R. Watanabe; H. Nojiri; T. Nogami; T. Ishida
Oral presentation, English, 11th International Conference on Molecule-based Magnets
Sep. 2008 - Structures and Magnetic Properties of Tetra- and Polynuclear Copper(II) Complexes Bridged with Imidazolate Rings
N. Koyama; R. Watanabe; T. Ishida; T. Nogami; T. Kogane
Oral presentation, English, 11th International Conference on Molecule-based Magnets
Sep. 2008 - High-Field ESR on Molecular-Based Nano-Magnets --- Application to Polyhedron Clusters and Rare-Earth Compounds
Y. Oshima; H. Nojiri; S. Yoshii; P. Kogerler; M. Luban; A. Muller; J. Schnack; A. Okazawa; T. Ishida
Oral presentation, English, Asian-Pacific EPR/ESR Symposium
Jul. 2008 - muSR Study on Cobalt(II)-Radical Low-Dimensional Magnets
T. Ishida
Oral presentation, English, The 3rd Program Advisory Committee Meeting for Materials and Life Science
2008 - Exchange Coupling and Energy-Level Crossing of 4f-3d Heterometallic Coordination Compounds
T. Ishida; H. Nojiri
Oral presentation, English, KINKEN Research Highlights 2008
2008 - Muon Spin Rotation and Relaxation on the One-Dimensional Cobalt(II)-Radical Coordination Polymer Magnet
T. Ishida; Y. Okamura; I. Watanabe
Oral presentation, English, RIKEN-RAL Muon Facility Report
2008 - High-Frequency EPR Study on a 4f-3d Single-Chain Magnets [Dy2Cu2]n
A. Okazawa; T. Nogami; H. Nojiri; T. Ishida
Oral presentation, English, 21st Century COE Program International Symposium on Coherent Optical Science
Dec. 2007 - Ferro-/Antiferromagnetic Coupling Switch Accompanied by Single-Crystal-to-Single-Crystal Phase Transition in [Cu2(2pyNO)4](BF4)2
T. Ishida; A. Okazawa; T. Nogami; D. Hashizume
Oral presentation, English, A Joint Conference of the International Symposium on Electron Spin Science and the 46th Annual Meeting of the Society of Electron Spin Science and Technology
Nov. 2007 - Exchange Coupling and Energy-Level Structure of 4f-3d Heterometallic Single-Molecule Magnets by High-Frequency EPR
A. Okazawa; T. Nogami; H. Nojiri; T. Ishida
Oral presentation, English, A Joint Conference of the International Symposium on Electron Spin Science and the 46th Annual Meeting of the Society of Electron Spin Science and Technology
Nov. 2007 - A Family of Nitronyl Nitroxide-Co(II) Chain Complexes Showing Giant Coercivity
Y. Okamura; T. Ishida; T. Nogami
Oral presentation, English, A Joint Conference of the International Symposium on Electron Spin Science and the 46th Annual Meeting of the Society of Electron Spin Science and Technology
Nov. 2007 - Study on Chelate Complexes Involving Heteroaromatic Nitroxides
Y. Terakado; A. Okazawa; T. Nogami; T. Ishida
Oral presentation, English, A Joint Conference of the International Symposium on Electron Spin Science and the 46th Annual Meeting of the Society of Electron Spin Science and Technology
Nov. 2007 - Spin-crossover Behavior Coupled with Mesophase Transition for Iron(II) Thiocyanate Complexes Chelated with 2-Pyridylmethyleneanilines
Y. Oso; S. Saito; T. Ishida; T. Nogami
Oral presentation, English, A Joint Conference of the International Symposium on Electron Spin Science and the 46th Annual Meeting of the Society of Electron Spin Science and Technology
Nov. 2007 - Electron Density Distributions of Intermolecular N...O Contacts in Crystals of Biphenyl-3,5-diyl bis(t-butyl nitroxide)
M. Yasui; S. Mashiyama; K. Ozawa; H. Hosoya; H. Nishimaki; G. Kurokawa; T. Ishida; T. Nogami
Oral presentation, English, Joint Conference of the Asian Crystallographic Association and the Crystallographic Association of Japan, Tsukuba, International conference
Nov. 2006 - Magnetic Properties of Molecular Magnets and Spin Chains Studied by Moessbauer Spectroscopy
H.-H. Klauss; F. Gouider; J. Kreitlow; S. Suellow; F. J. Litterst; T. Ishida; T. Nogami; K. Doll; D. J. Price
Oral presentation, English, Latin American Conference on the Applications of the Moessbauer Effects, Rio de Janeiro, Brazil, International conference
Nov. 2006 - Mono- and Dinitroxide radicals from 9,9’(10H,10’H)-spirobiacridine: An Approach to a D2d Triplet Biradical
T. Ishida; N. Ishii; H. Mori; M. Ooishi; T. Nogami
Oral presentation, English, 10th international Conference on Molecule-based Magnets
Aug. 2006 - Tetranuclear Copper(II) Complexes Sandwitched with Two Tetrahydropyran-2,4,6-triolate Ligands
Y. Morishita; T. Ishida; T. Nogami; T. Kogane
Oral presentation, English, 10th international Conference on Molecule-based Magnets
Aug. 2006 - Tetranuclear Heterometallic Cycle Dy2Cu2 Showing Slow Relaxation of Magneitzation Reorientation
S. Ueki; T. Ishida; T. Nogami
Oral presentation, English, 10th international Conference on Molecule-based Magnets
Aug. 2006 - Preparation, Structure, and Magnetic Properties of Chelating Compounds of 2-Pyridyl Nitroxide Derivatives
A. Okazawa; T. Shimada; T. Ishida; T. Nogami
Oral presentation, English, 10th international Conference on Molecule-based Magnets
Aug. 2006 - Structures and Magnetic Properties of One-dimensional Copper(II) Complexes Bridged with Diazaaromatic Rings
T. Kogane; N. Koyama; T. Ishida; T. Nogami
Oral presentation, English, 10th international Conference on Molecule-based Magnets
Aug. 2006 - Electron Donors from Natural Products: Donating Ability and Charge Transfer Complexes of Vargula and Firefly Luciferins
T. Ishida; M. Suzuki; T. Fujii; T. Nogami; T. Hirano
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - Cyclen and Cyclam Spin-Labels Showing Magnetic Exchange Interactions Tuned by Diamagnetic Metal Ions
K. Igarashi; T. Ishida; T. Nogami
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - "tert-Butyl 2-Pyridyl Nitroxides as Paramagnetic Chelating Ligands
A. Okazawa; K. Osanai; K. Yanagi; T. Shimada; T. Nogami; T. Ishida
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - One-dimensional Copper(II) Complexes Bridged with Diazaaromatic Rings
T. Kogane; T. Nogami; T. Ishida
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - One-dimensional Complexes of Hydro Nitronyl Nitroxide and Co(hfac)2 Showing Polymorphs and Magnetic Hysteresis
N. Ishii; T. Ishida; T. Nogami
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - Rectangular Tetraterbium- and Tetradysprosium-Copper Complex Ions Behaving as Single-Molecule Magnets
S. Ueki; T. Ishida; T. Nogami; K.-Y. Choi; H. Nojiri
Oral presentation, English, The 2005 International Chemical Congress of Pacific Basin Societies
Dec. 2005 - ET Salts with Lanthanide Complex Ion Showing Frequency-Dependent ac Magnetic Susceptibility
T. Ishida; S. Ueki; T. Nogami; M. Tamura
Oral presentation, English, Organic Semiconductors and Conductors: Half Century and Future Prospects
Aug. 2005 - Light-Induced Magnets from Organic and Organic-Inorganic-Hybrid Approaches
Y. Morishita; T. Ishida; T. Nogami
Oral presentation, English, Inernational Symmposium on Coherent Optical Science
Jul. 2005 - Effect of Staggered Field on the Magnetization Process of S = 1/2 Antiferromagnetic Chains
A. Matsuo; K. Hosokawa; Y. Narumi; K. Okunishi; N. Maeshima; T. Asano; Y. Ajiro; T. Ishida; T. Nogami; K. Kindo
Oral presentation, English, International Symposium on Quantum Spin Systems 2004 (Hayama)
Nov. 2004 - 超分子的に制御できる分子磁性
石田尚行; 野上 隆
Invited oral presentation, Japanese, 日本応用磁気学会学術講演会, 日本応用磁気学会, Domestic conference
Sep. 2004 - 3d-4f Approach to SMMs. Heterometallic Complexes Containing Oximate Bridges
F. Mori; S. Ueki; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Magnetic Properties of Transition Metal Complexes with 2,2'-Bipyridin-4-yl t-Butyl Nitroxide
T. Ishida; T. Shimada; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Magnetic Coupling Switch by Means of Host-Guest Chemistry in a Crown-ether Side-arm
T. Ishida; T. Nakabayashi; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Structure and Magnetic Properties of 3d - 4f Hetero-metallic Complexes Containing Di-2-pyridyl Ketoximate
F. Mori; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Short Spiral Structure of Linear Trinuclear Complexes [Ni3(pzNN)6] and [Ni3(pzIN)6]
S. Yamada; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Structures and Magnetic Properties of Dinuclear Spiro-complexes for Orthogonality of Magnetic Orbitals
A. Okazawa; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Structure and Magnetic Property of Honeycomb-like Complex
K. Osanai; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Molecule-based Magnets 2004
Aug. 2004 - Nano-sized [Ln4Cu1] complex ions containing oximato bridges (Ln = lanthanoid)
T. Ishida; S. Ueki; M. Sahlan; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals 2004
Jun. 2004 - Rectangular Tetralanthanide Ln4Cu1 Complexes (Ln = Nd, Gd) Containing Bis(dimethylglyoximato)copper(II) as a Template in Synthesis and a Coupler in Magnetic Exchange
Y. Kobayashi; T. Ishida; T. Nogagmi
Oral presentation, English, Nano-Science of Advanced Metal Complexes
Mar. 2003 - Meta-Phenylene-Bridged Bis(iminonitroxide) Biradicals as Potential High-Spin Ligands
T. Ishida; T. Ichimura; T. Nogami
Oral presentation, English, VIIIth International Conference on Molecule-Based Magnets
Oct. 2002 - Host-Guest Chemistry of Radical-Copper Wheels. a Supramolecular Control of Magnetic Exchange Coupling
T. Ishida; J.-i. Omata; T. Nogami
Oral presentation, English, VIIIth International Conference on Molecule-Based Magnets
Oct. 2002 - Canted Antiferromagnetism in TPM2X2: a Microscopic Study
J. Kreitlow; A. Wolter; D. Baabe; H.-H. Klauss; S. Sulow; D. Mienert; J. Litterst; R. Feyerherm; K. Doll; T. Ishida; M. A. C. de Melo; A. Amato
Oral presentation, English, VIIIth International Conference on Molecule-Based Magnets
Oct. 2002 - Magnetic Structures of Transitiion Metal Complex Compounds Determined by Neutron Diffraction
R. Feyerherm; A. Loose; T. Ishida; J. Li; P. Rabu
Oral presentation, English, VIIIth International Conference on Molecule-Based Magnets
Oct. 2002 - Structures and Magnetic Properties of Molecule-Based Magnetic Materials
T. Nogami; T. Ishida
Oral presentation, English, International Workshop on Modern Science and Technology 2002
Sep. 2002 - Effect of Staggered Field in S = 1/2 Antiferromagnetic Chain: Copper Pyrimidine
T. Asano; D. Nomura; Y. Inagaki; Y. Ajiro; H. Nojiri; Y. Narumi; K. Kindo; T. Ishida; T. Nogami
Oral presentation, English, The 23rd International Conference on Low Temperature Physics
Aug. 2002 - Preparation and Characterization of Bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)copper(II) Complexes with Diazanaphthalenes
T. Kogane; T. Ishida; T. Nogami
Oral presentation, English, 35th International Conference on Coordination Chemistry
Jul. 2002 - Hydroiminonitroxide Complexes with Metal Hexafluoroacetylacetonates
T. Ise; T. Ishida; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jun. 2002 - Solvated Magnets of Fe[N(CN)2]2(pyrimidine): Transition Phenomena Tuned by Guests
T. Kusaka; T. Ishida; T. Nogami
Oral presentation, English, International Symposium on Cooperative Phenomena of Assembled Metal Complexes, 15-17, Nov. 2001, Osaka
Nov. 2001 - Structures and Magnetic Properties of Pyrimidine-Bridged Transition-Metal Complexes
T. Nogami; T. Ishida
Oral presentation, English, The 7th Japan-China Joint Symposium on Conduction and Photo-conduction in Organic Solids and Related Phenomena
Nov. 2001 - Low Temperature Deuterium NMR Studies on Magnetism of TEMPO Derivatives
G. Maruta; S. Takeda; M. Ooishi; R. Imachi; T. Ishida; T. Nogami
Oral presentation, English, The Fourth International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets
Sep. 2001 - Hybrid Magnetic Solids of Radical-Substituted Heteroaromatic Compounds with Metal Halides
T. Matsuyama; Y. Iwata; J. Sata; J. Omata; T. Ishida; T. Nogami
Oral presentation, English, The Fourth International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets
Sep. 2001 - Magnetic Properties of 9,9-Disubstituted 9,10-Dihydroacridine-10-yloxyls
M. Seino; Y. Akui; T. Ishida; T. Nogami
Oral presentation, English, The Fourth International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets
Sep. 2001 - Single crystal studies of the 1-D systems PMCu(NO3)2(H2O)2 and MnNi(NO2)4(en)
R. Feyerherm; A. Loose; T. Ishida; T. Nogami; C. Mathoniere; O. Kahn
Oral presentation, English, Conference on the European Science Foundation Programme
Mar. 2001 - Crystal and magnetic structures of FePM2Cl2, Co(ox)(bpy) and MCl2(bpy), M = Co, Ni, determined by neutron powder diffraction mid-term
A. Loose; R. Feyerherm; T. Ishida; M. A. Lawandy; J. Li
Oral presentation, English, Conference on the European Science Foundation Programme
Mar. 2001 - Magnetische ordnung molekularer u¨ergangsmetallkomplexe
R. Feyerherm; A. Loose; C. Mathonie ́re; O. Kahn; T. Ishida
Oral presentation, Fru¨hjahrstagung des Arbeitskreises Festko¨rperphysik der Deutsche Physikalische Gesellschaft (Hamburg)
Mar. 2001 - Magnetic-field induced gap and staggered susceptibility in the S=1/2 chain [PM.Cu(NO3)2(H2O)2]n (PM = pyrimidine)
R. Feyerherm; M. Meissner; T. Ishida
Oral presentation, Fru¨hjahrstagung des Arbeitskreises Festko¨rperphysik der Deutsche Physikalische Gesellschaft
Mar. 2001 - Magnetic Properties of Some Transition-Metal Complexes
T. Nogami; T. Ishida
Oral presentation, English, The IMS COE Symposium on Electronic Properties of Molecular Assemblies - from Molecular Solid to Single Molecule -
Mar. 2001 - Magnetic Properties of 9,9'(10H,10'H)-spirobiacridine-10,10'-dioxyl and Related Compounds
T. Ishida; M. Ooishi; T. Nogami
Oral presentation, English, The IMS COE Symposium on Electronic Properties of Molecular Assemblies - from Molecular Solid to Single Molecule -
Mar. 2001 - Magnetic structure of Mn(dca)2(pyz-d8) and other molecular magnets
R. Feyerherm; A. Loose; P. Smeibidl; S. Raasch; D. Tu ̈bens; J. L. Manson; T. Ishida
Oral presentation, English, BENSC Experimental Reports 2001, Hahn-Meitner-Institut Berlin, Germany
2001 - Synthesis and Properties of Dibenzodioxadithiafulvalene and Related Compounds
K. Tanaka; K. Mondo; T. Ishida; A. Kobayashi; T. Nogami
Oral presentation, English, The 2000 International Chemical Congress of Pacific Basin Societies
Dec. 2000 - Magnetic Phase Transition of Fe(II) and Co(II) Complexes Bridged by Pyrimidine and Dicyanamide
T. Kusaka; T. Ishida; D. Hashizume; F. Iwasaki; T. Nogami
Oral presentation, English, The 2000 International Chemical Congress of Pacific Basin Societies
Dec. 2000 - High-Spin Radical-Copper Macrocycles and Related Compounds
J. Omata; T. Ishida; D. Hashizume; F. Iwasaki; T. Nogami
Oral presentation, English, The 2000 International Chemical Congress of Pacific Basin Societies
Dec. 2000 - Structures and Magnetic Properties of Transition-Metal Complexes
T. Nogami; T. Ishida
Oral presentation, English, International Workshop on Magnetism in Lower Dimensions 2000
Dec. 2000 - Anomalous Magnetism in Organic Radical Ferromagnets 4-Arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyl just above Tc studied by mSR method
S. Ohira; T. Ise; K. Nakayama; T. Ishida; T. Nogami; I. Watanabe; K. Nagamine
Oral presentation, English, VII th International Conference on Molecule-Based Magnets (Texas)
Sep. 2000 - 1-Dimensional S=1 Ferromagnetic Chain Formed by a Square Ni2S2 Motif in Ni(qt)2 (qt = Quinoline-8-thiolate)
T. Miyake; T. Ishida; D. Hashizume; F. Iwasaki; T. Nogami
Oral presentation, English, VII th International Conference on Molecule-Based Magnets (Texas)
Sep. 2000 - Radical-Copper Macrocycles with a Ground High-Spin State
J. Omata; T. Ishida; D. Hashizume; F. Iwasaki; T. Nogami
Oral presentation, English, VII th International Conference on Molecule-Based Magnets (Texas)
Sep. 2000 - Zero-Field Muon Spin Rotation Study on TEMPO-Based Magnets, Ar-CH=N-TEMPO (Ar = 4-Biphenylyl, Phenyl, and 4-Pyridyl)
T. Ishida; S. Ohira; T. Ise; K. Nakayama; I. Watanabe; T. Nogami; K. Nagamine
Oral presentation, English, VII th International Conference on Molecule-Based Magnets (Texas)
Sep. 2000 - Channel Structure Formed by High-Spin Radical Copper Wheels
T. Ishida; J. Omata; D. Hashizume; F. Iwasaki; T. Nogami
Oral presentation, English, XI th International Symposium on Supramolecular Chemistry
Jul. 2000 - Muon Spin Resonance Study on Muonium and Mu-like Radical States in a TEMPO Derivative
S. Ohira; T. Ishida; T. Nogami; K. Nagamine
Oral presentation, English, KEK-MSL Report 1999
May 2000 - mSR Study on Crytical Behavior of Organic Radical Magnets, 4-Arylmethyleneamino-TEMPO
S. Ohira; T. Ise; Y. Akui; T. Katayama; T. Miyake; T. Ishida; T. Nogami; I. Watanabe; K. Nagamine
Oral presentation, English, KEK-MSL Report 1999
May 2000 - mSR Study on 4-Py-CH=N-TEMPO
S. Ohira; T. Ise; T. Katayama; T. Miyake; T. Ishida; T. Nogami; I. Watanabe; K. Nagamine
Oral presentation, English, KEK-MSL Report 1999
May 2000 - μSR Studies on Low Dimensionality of Organic Radical Magnets (R104)
S. Ohira; I. Watanabe; F. L. Pratt; K. Nagamine; T. Ishida; T. Nogami
Oral presentation, English, RIKEN-RAL Muon Facility Reort
2000 - μSR Study on Organic Radical Ferromagnets, 4-Arylmethyleneamino-TEMPO (R62)
S. Ohira; I. Watanabe; K. Nagamine; K. Nakayama; T. Ishida; T. Nogami
Oral presentation, English, RIKEN-RAL Muon Facility Reort
2000 - Report
S. Ohira; T. Ishida; T. Nogami; I. Watanabe; K. Nagamine
Oral presentation, English, RIKEN Accel. Prog. Rep.
2000 - Ferromagnetism and Exchange Mechanism of Organic Nitroxide Crystals
T. Ishida
Oral presentation, English, International Workshop on Magnetism in Lower Dimensions
Dec. 1999 - Magnetism of Pyrimidine-Bridged Transition-Metal Complexes
K. Zusai; T. Ishida; T. Nogami
Oral presentation, English, International Symposium on Molecular Design and Assembled Metal Complexes
Nov. 1999 - Magnetic Phase Transition of Py2N- and NCNH--Bridged Nickel (II) Complexes at about 25 K
K. Zusai; T. Katayama; T. Ishida; T. Nogami
Oral presentation, English, International Symposium on Molecular Design and Assembled Metal Complexes
Nov. 1999 - μSR studies on critical behavior of organic radical magnet, 4-(p-chlorobenzylideneamino)- 2,2,6,6-tetramethylpiperidin-1-yloxyl
S. Ohira; I. Watanabe; K. Nakayama; T. Ishida; T. Nogami; K. Nagamine
Oral presentation, English, RIKEN Review
Nov. 1999 - Muon Spin Relaxation and Resonance Studies on the Organic Radical Magnet, 4-Arylmethyleneamino-TEMPO
S. Ohira; I. Watanabe; F. L. Pratt; T. Ishida; T. Nogami; K. Nagamine
Oral presentation, English, 8th International Conference on Muon Spin Rotaion, Relaxation and Resonance
Aug. 1999 - Solid-State high-Resolution 2H NMR Study of Electron Spin Density Distribution of Organic Ferromagnets
G. Maruta; S. Takeda; R. Imachi; T. Ishida; T. Nogami; K. Yamaguchi
Oral presentation, English, The 4th International Symposium on Functional Dyes -Science and Technology of Functional p-Electron Systems-
May 1999 - Ferromagnetic Interaction of Organic Radicals and Pyrimidine-Bridged Transition-Metal Complexes
T. Nogami; T. Ishida
Oral presentation, English, The 4th International Symposium on Functional Dyes -Science and Technology of Functional p-Electron Systems-
May 1999 - Long-range ordered state of organic radical magnets 4-Arylmethyleneamino-TEMPO
S. Ohira; T. Ishida; T. Ise; Y. Akui; T. Nogami; I. Watanabe; K. Nagamine
Oral presentation, English, KEK-MSL REPORT 1998
1999 - Crystal Structures of Phenanthridine and Acridine Derivatives wiht Magnetic Interacations
M. Suzuki; D. Hashizume; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, The 3rd Conferenece of the Asian Crystallographic Association
Oct. 1998 - Intermolecular Ferromagnetic Interaction of p-Conjugated Nitroxide Radicals
T. Ishida; T. Nogami
Oral presentation, English, The 6th Japan-China Joint Symposium on Conduction and Photo-conduction in Organic Solids and Related Phenomena
Oct. 1998 - Intermolecular Ferromagnetic Interaction in pai-Conjugated Nitroxide Radical Crystals
T. Ishida; Y. Akui; S.-y. Masaoka; M. Nakagawa; D. Hashizume; M. Yasui; F. Iwasaki; T. Nogami
Oral presentation, English, The VIth International Conference on Molecule-Based Magnets
Oct. 1998 - Spin Density of a Ferromagnetic TEMPO Derivative
Y. Pontillon; E. Ressouche; J. Schweizer; T. Ishida; T. Nogami
Oral presentation, English, The VIth International Conference on Molecule-Based Magnets
Sep. 1998 - Pressure Effects of Organic Ferromagnetic Radical p-Cl-C6H4-CH=N-TEMPO
M. Mito; T. Kawae; K. Takeda; T. Ishida; T. Nogami
Oral presentation, English, The VIth International Conference on Molecule-Based Magnets
Sep. 1998 - Single Crystal Magnetic Susceptibility of 1-D [PM.Cu(NO3)2.(H2O)2]n
R. Feyerherm; T. Ishida; T. Nogami; M. Steiner
Oral presentation, English, The VIth International Conference on Molecule-Based Magnets
Sep. 1998 - Magnetic Phase Transition of Copper Complexes Containing dmit or TCNQ anion
T. Ishida; Y. Kokubo; K. Nakayama; T. Nogami
Oral presentation, English, The VIth International Conference on Molecule-Based Magnets
Sep. 1998 - Very Low-Temperature Heat Capacity and Magnetic Phase Transition of the Organic Ferromagnet, CMTMP
M. Sorai; Y. Miyazaki; T. Matsumoto; T. Ishida; T. Nogami
Oral presentation, English, 15th International Conference on Chemical Thermodynamics (Portugal)
Jul. 1998 - μSR Study on Organic Radical Ferromagnets 4-(Arylmethyleneamino)-TEMPO
S. Ohira; I. Watanabe; K. Nakayama; T. Ishida; T. Nogami; K. Nagamine
Oral presentation, English, KEK-MSL Report 1997
1998 - Crystal Structures of 4-(4-Halobenzylideneamino)-TEMPO Radicals Showing Ferromagnetic Interactions
F. Iwasaki; H. Yamamoto; H. Yoshikawa; T. Takada; H. Kannari; M. Yasui; T. Ishida; T. Nogami
Oral presentation, English, 13th International Conference on the Chemistry of the Organic Solid State (NY)
Jul. 1997 - Physical Properties of ET Salts with Organic Anions
M. Luo; S. Sakakura; T. Ishida; T. Nogami
Oral presentation, English, Recent Development and Future Prospect of Molecular Based Conductors
Mar. 1997 - Crystal Structures of Copper Complexes Showing Magnetic Interaction
Y. Ishikawa; M. Yasui; T. Nogami; T. Ishida; F. Iwasaki
Oral presentation, English, International Symposium 'Analysis and Design of Solid-State Organic Reactions
Sep. 1996 - Crystal Structures of TEMPO Radicals Showing Magnetic Interactions
H. Yamamoto; H. Yoshikawa; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, International Symposium 'Analysis and Design of Solid-State Organic Reactions
Sep. 1996 - Crystal Structures of Copper Complexes Showing Ferromagnetic Interaction
M. Yasui; Y. Ishikawa; T. Nogami; T. Ishida; F. Iwasaki
Oral presentation, English, 17th Congress of the International Union of Crystallography (Seatle)
Aug. 1996 - Crystal Structures of TEMPO Radicals Showing Ferromagnetic Interactions
H. Yamamoto; H. Yoshikawam; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, 17th Congress of the International Union of Crystallography (Seatle)
Aug. 1996 - Electrical Conductivities of MOTT Salts
T. Nogami; K. Yoshida; T. Ishida; A. Kobayashi
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 1996 - Magnetic Properties of Pyrimidine-Bridged Copper(II) Nitrate Complexes
T. Ishida; K. Nakayama; W. Saito; M. Yasui; F. Iwasaki; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 1996 - Magnetic Interaction via β-Hydrogen Atoms in TEMPO Derivatives
T. Kawakami; A. Oda; S. Takeda; W. Mori; T. Ishida; T. Nogami; K. Yamaguchi
Oral presentation, English, The Vth International Conference on Molecule-Based Magnets
Jul. 1996 - Solid State 1H-MAS-NMR and Spin Densities on Protons of the Organic Ferromagnetic TEMPO Derivatives
G. Maruta; S. Takeda; T. Kawakami; W. Mori; K. Yamaguchi; R. Imachi; T. Ishida; T. Nogami
Oral presentation, English, The Vth International Conference on Molecule-Based Magnets
Jul. 1996 - Ferromagnetism of Organic Radical Crystals of Perdeuterated TEMPO Derivatives
R. Imachi; T. Ishida; T. Nogami; M. Yasui; F. Iwasaki; N. Takeda; M. Ishikawa
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 1996 - Magnetic Properties of Pyrimidine-Bridged Copper(II) Complexes
T. Ishida; M. Nakagawa; K. Nakayama; Y. Ishikawa; M. Yasui; F. Iwasaki; T. Nogami
Oral presentation, English, The Vth International Conference on Molecule-Based Magnets
Jul. 1996 - Magnetic Properties of 4- and 5-Methylpyrimidine-Bridged Copper(II) Complexes
M. Nakagawa; Y. Ishikawa; T. Kogane; T. Ishida; M. Yasui; F. Iwasaki; T. Nogami
Oral presentation, English, Perspective in Organic-inorganic Hybrid Solids ---Molecular Design and Functionality---
Mar. 1996 - Ferromagnetism of Organic Radical Crystals of TEMPO Derivatives
T. Nogami; T. Ishida; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, The 1996 International Chemical Congress of Pacific Basin Societies
Dec. 1995 - Ferromagnetism of Pyrimidine-Bridged Copper(II) Complexes
T. Ishida; T. Nogami; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, The 1996 International Chemical Congress of Pacific Basin Societies
Dec. 1995 - Crystal Structures of Copper Complexes Showing Ferromagnetic Interaction
Y. Ishikawa; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, 2nd Conference of the Asian Crystallographic Association (Bangkok)
Nov. 1995 - Crystal Structures of TEMPO Radicals Showing Ferromagnetic Interaction
H. Yamamoto; H. Yoshikawa; H. Mitsuda; K. Takada; M. Yasui; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, 2nd Conference of the Asian Crystallographic Association (Bangkok)
Nov. 1995 - Syntheses, Crystal Structures, and Magnetic Properties of Organic Ferromagnets: A Series of Arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-oxyls and Pyrimidine-Bridged Transition-Metal Complexes
T. Nogami; T. Ishida; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, Recent Progress and Future Prospects of Molecular Electronic Spectroscopy
Oct. 1995 - Crystal Structures of TEMPO Radicals Showing Ferromagnetic Interaction
M. Yasui; H. Yoshikawa; H. Yamamoto; T. Ishida; T. Nogami; F. Iwasaki
Oral presentation, English, 12th International Conference on the Chemistry of the Organic Solid State
Jul. 1995 - Ferromagnetism of Organic Radical Crystals of TEMPO Derivatives
T. Nogami; T. Ishida; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, 12th International Conference on the Chemistry of the Organic Solid State
Jul. 1995 - Ferromagnetism of Pyrimidine-Bridged Copper(II) Complexes
T. Ishida; T. Nogami; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, 12th International Conference on the Chemistry of the Organic Solid State
Jul. 1995 - Synthesis and Molecular Structures of New Multi-Sulfur Donor Molecules and Acceptor Molecules, and Electrical Conductivities of Their Ion-Radical Salts
T. Nogami; T. Ishida; M. Tanaka; K. Yoshida; M. Takebayashi; H. Yoshikawa; M. Yasui; F. Iwasaki
Oral presentation, English, International Symposium on Novel Electonic States in Molecular Conductors
Aug. 1994 - Intra- and Inter-Molecular Ferromagnetic Interaction of Transition Metal Complexes Containing Pyrimidine or Pyrazine Derivatives
T. Ishida; S.-i. Mitsubori; N. Takeda; M. Ishikawa; H. Iwamura; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 1994 - New Organic Ferromagnets: 4-Arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (Aryl = Phenyl, 4-Biphenyl)
T. Nogami; K. Togashi; H. Tsuboi; T. Ishida; H. Yoshikawa; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Jul. 1994 - Molecular Ferromagnet(1). Magnetic Properties of VO･Pyrimidine and Cu･Quinazoline Complexes
T. Ishida; T. Nogami; S.-i. Mitsubori; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, Japanese, Summer Symposium on Functional Materials
Jul. 1994 - Molecular Ferromagnet(1). Crystal Structures and Magnetic Properties of TEMPO radicals Coneected with Various Aromatic Rings through an Azomethine Linkage
T. Nogami; T. Ishida; H. Yoshikawa; M. Yasui; F. Iwasaki; H. Iwamura; N. Takeda; M. Ishikawa
Oral presentation, Japanese, Summer Symposium on Functional Materials
Jul. 1994 - Synthesis and Characterization of C60 Adducts with Benzyne, Dichlorocarbene, Dienes, and Oxygen
T. Nogami; M. Tsuda; T. Ishida; S. Kurono; M. Ohashi
Oral presentation, English, The 3rd IUMRS International Conference on Advanced Materials
Jun. 1993 - Approaches from High-Spin Organic Molecules to Organic Ferromagnets
T. Ishida; K. Inoue; N. Koga; N. Nakamura; H. Iwamura
Oral presentation, English, Matrials Research Society Symposium
Nov. 1992 - Intermolecular Ferromagnetic Interaction of 4-(1-Pyrenylmethyleneamino)-2,2,6,6- tetramethylpiperidin-1-oxyl and Magnetic Interaction of Transition Metal Ions in Complexes Containing Pyrimidine or Pyrazine as a Bridging Ligand
T. Ishida; S.-I. Mitsubori; K. Tomioka; T. Nogami; H. Iwamura; K. Yamaguchi; W. Mori; Y. Shirota
Oral presentation, English, International Symposium on Chemistry and Physics of Molecular Based Magnetic Materials
Oct. 1992 - Synthesis of Multi-Sulfur TTF Derivatives and Cunducting Organic Salts
T. Nogami; T. Ishida; H. Yoshikawa; M. Tanaka; T. Naito; H. Kobayashi; A. Kobayashi
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Aug. 1992 - Attempted Syntheses of Dibenzotetraoxafulvalene
T. Ishida; Y. Ishihara; T. Yamaga; T. Nogami
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Aug. 1992 - Syntheses, Second-Order NLO properties, and Crystal Structures of Tetrasubstituted Ethylene, Trisubstituted Schiff-Base, and Diphenoxymethane Derivatives
T. Ishida; H. Osaka; T. Nogami; R. Yamazaki; M. Yasui; F. Iwasaki; A. Mizoguchi; M. Kuhata; T. Uemiya; A. Nishimura
Oral presentation, English, International Conference on Science and Technology of Synthetic Metals
Aug. 1992 - Design of Organic Ferromagnets Based on High-Spin Poly(phenylacetylenes) Having Radical Centers on the Side Chains
H. Iwamura; N. Koga; T. Ishida
Oral presentation, English, The 1989 International Chemical Congress of Pacific Basin Societies
Dec. 1989 - Synthesis and Properties of Poly(ethynylphenyl Nitroxide) Derivatives
T. Ishida; H. Iwamura
Oral presentation, English, The 1989 International Chemical Congress of Pacific Basin Societies
Dec. 1989 - Unusually Facile Cleavage of S-Cα Bond in Highly Sterically Crowded Sulfoxides
T. Ishida; R. Okazaki; N. Inamoto
Oral presentation, English, First International Conference on Heteroatom Chemistry
Jul. 1987
Courses
- Practical advanced instrumental analysis
The University of Electro-Communications - 実践的先進機器分析
電気通信大学 - Graduate Technical English
The University of Electro-Communications - 大学院技術英語
電気通信大学 - Inorganic Chemistry
The University of Electro-Communications - General Chemistry
The University of Electro-Communications - Advanced Solid State Chemistry
The University of Electro-Communications - Exercises in Chemistry and Biotechnology II
The University of Electro-Communications - 化学生命工学演習第二
電気通信大学 - Chemistry and Biotechnology Laboratory II
The University of Electro-Communications - 化学生命工学実験第二
電気通信大学 - Exercises in Chemistry and Biotechnology I
The University of Electro-Communications - 化学生命工学演習第一
電気通信大学 - Principles of Chemistry Ⅰ
The University of Electro-Communications - Chemistry Laboratory
The University of Electro-Communications - 化学概論第一
The University of Electro-Communications - 化学概論第一
電気通信大学 - 無機化学（III類）
The University of Electro-Communications - 創成物理化学特別講義2
大阪市立大院理学系研究科 - 創成物理化学特別講義2
大阪市立大院理学系研究科 - 無機化学（III類）
The University of Electro-Communications - 無機化学（III類）
電気通信大学 - 固体物性化学特論
The University of Electro-Communications - 無機化学（生体機能システムコース）
The University of Electro-Communications - 無機化学（生体機能システムコース）
電気通信大学 - 生体機能システム演習第二
The University of Electro-Communications - 固体物性化学特論
The University of Electro-Communications - 固体物性化学特論
電気通信大学 - 現代化学
The University of Electro-Communications - 生体機能システム演習第二
The University of Electro-Communications - 生体機能システム演習第二
電気通信大学 - 化学概論
The University of Electro-Communications - 化学概論
電気通信大学 - 特別講義無機化学特論Ａ
神戸大院理学研究科 - 特別講義無機化学特論Ａ
神戸大院理学研究科 - 生体機能システム実験第二
The University of Electro-Communications - 物質工学演習B
The University of Electro-Communications - 有機物質工学第二
The University of Electro-Communications - 大学院総合コミュニケーション科学
The University of Electro-Communications - 生体機能システム演習第一
The University of Electro-Communications - 固体化学特論
The University of Electro-Communications - 量子・物質工学実験A
The University of Electro-Communications - 物質材料科学A
The University of Electro-Communications - 無機化学
The University of Electro-Communications - 基礎科学実験B
The University of Electro-Communications - 大学院総合コミュニケーション科学
The University of Electro-Communications - 大学院総合コミュニケーション科学
電気通信大学 - 生体機能システム実験第二
The University of Electro-Communications - 生体機能システム実験第二
電気通信大学 - 現代化学
The University of Electro-Communications - 現代化学
電気通信大学 - 物質工学演習B
The University of Electro-Communications - 物質工学演習B
電気通信大学 - 有機物質工学第二
The University of Electro-Communications - 有機物質工学第二
電気通信大学 - 生体機能システム演習第一
The University of Electro-Communications - 生体機能システム演習第一
電気通信大学 - 固体化学特論
The University of Electro-Communications - 固体化学特論
電気通信大学 - 量子・物質工学実験A
The University of Electro-Communications - 量子・物質工学実験A
電気通信大学 - 物質材料科学A
The University of Electro-Communications - 物質材料科学A
電気通信大学 - 無機化学
The University of Electro-Communications - 無機化学
電気通信大学 - 基礎科学実験B
The University of Electro-Communications - 基礎科学実験B
電気通信大学
Affiliated academic society
Research Themes
- スピンクロスオーバー高スピン相は磁気秩序相になりえるか？
石田 尚行
30 Jun. 2022 - 31 Mar. 2024 - 希土類有機ラジカルフレームワーク（RERF）の創製と室温動作機能性磁石への展開
石田尚行
村田学術振興財団, 研究助成
Sep. 2022 - Aug. 2023 - ソフトクリスタル化学発光系の創製と刺激応答機能の時空間制御
平野 誉
01 Dec. 2020 - 31 Mar. 2022 - 希土類有機ラジカルフレームワーク（RERF）と室温動作機能性磁石の創製
石田尚行
01 Aug. 2020 - 31 Mar. 2022 - 単分子磁石自動集積による高保磁力高ブロッキング温度複合磁性材料の創製
石田尚行
泉科学技術振興財団, 研究助成, Principal investigator
01 Oct. 2019 - 30 Sep. 2021 - ポリマー関係学術相談
石田尚行
私企業, 学術相談, Principal investigator
01 Jul. 2018 - 31 Mar. 2019 - 希土類錯体の常磁性・反磁性配位子による発光性能と磁石性能のスイッチ
石田尚行
池谷科学技術振興財団, 研究助成, Principal investigator
01 Apr. 2018 - 31 Mar. 2019 - 僅かな分子の構造変調が劇的なスピン状態変化をもたらす材料群の研究
石田尚行
Principal investigator
2015 - 2018 - エンジン関係共同研究
石田尚行
私企業, 研究助成, Principal investigator
01 Jul. 2013 - 31 Mar. 2014 - エンジン関係共同研究
石田尚行
私企業, 研究助成, Principal investigator
2012 - 2013 - 複合スピン機能と柔軟な有機機能を併せ持つ超分子的磁性体の合成開発とその評価
2010 - 2013 - エンジン関係依頼測定
石田尚行
私企業, 研究助成, Principal investigator
2012 - 2012 - へテロスピン系の特異な結合を利用した材料群の創出と構造相転移物質への展開
2011 - 2012 - 4f-3d-2pへテロスピン系の交換相互作用を利用した電子物性材料の創出
2009 - 2010 - ナノサイズ情報記録材料を目指した希土類金属イオンを含む単分子磁石および単一次元鎖磁石の開発
石田
カシオ
2009 - 2009 - 低次元構造をもちながら世界最高の保磁力を持つ分子性磁性体の研究
石田
日本証券
2009 - 2009 - 複合機能性材料を目指した超分子磁性体の開発
2007 - 2009 - Development of Single-molecule Magnets and Related Molecule-based Magents
NOGAMI Takashi; ISHIDA Takayuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), Single-molecule magnets (SMMs) and single-chain magnets (SCMs) attract much attention in materials chemistry. We have exploited potential utility of the bridging paramagnetic ligands (HIN, HNN, CnPNN). A strong character of SCM is operative in the magnetically ordered state in the one-dimensional Co-C4PNN complex, giving a largest class of the coercive field (52 kOe or 4.1 MA m-1 at 6 K). Several oligonuclear 3d-4f heterometallic complexes have been characterized as ground ferrimagnetic high-spin molecules. Lanthanide ions are supposed to be promising candidates for the elements of single-molecule magnets (SMMs) because of the large magnetic momentum and anisotropy. We have established the [Dy2Cu], [Dy4Cu], and [Dy2Cu2] complexes as new SMMs and [Dy2Cu2]n as a SCM. A plausible mechanism for quantum tunneling of magnetization has been proposed for the first time among the 3d-4f heterometallic SMMs and SCMs. The 3d-4f exchange magnetic couplings were precisely evaluated by means of high-frequency EPR spectroscopy. Another subject of the present research is multi-functional molecule-based magnets. Supramolecular techniques have been used to tune or control molecule-based magnetic materials. We have developed nano-porous magnetic materials, whose magnetic properties were changed by inclusion of small diamagnetic molecules. Switchable magnets by means of host-guest chemistry have been developed. Host-guest complexes of tri- and tetra-radical-substituted azamacrocycles afforded the folded structures of the hosts where the radical oxygen atoms were coordinated to the guest metal ion, leading to enhanced antiferromagnetic couplings in the solid state and an ESR line broadening in the solution phase., 17550166
2005 - 2007 - 多様な積層構造をもつフタロシアニンπ-d系導電体の構築
稲辺 保; 野上 隆; 石田 尚行; 内藤 俊雄
日本学術振興会, 科学研究費助成事業, 北海道大学, 特定領域研究, 本特定領域研究期間に以下の研究成果が得られた。 フタロシアニン(Pc)一次元π-d系:TPP[Fe(Pc)(CN)_2]_2の負の磁気抵抗を20Kで37Tまで測定し、2桁以上の抵抗低下を見出した。電気、磁気物性が軸配位子によって変化することを見出し、π-πおよびπ-d相互作用への軸配位子置換効果について実験および理論計算によって系統的に調べ、可変なπ-d系となることを見出した。一次元系での電荷の局在が不純物とは無関係であることを見出し、電荷の不均化が確認された。電流-電圧特性の測定により不均化の融解による非線形性が観測され、π-d系ではより高温から非線形性が顕著になり、電場によっても抵抗が激減することが見出された。 Pc二次元π-d系:[PXX]_2[Co(Pc)(CN)_2]・CH_3CNが等方的な二次元系であることを見出した。この結晶は半導体であるが、加圧によって金属的となる。二次元π-d系の構築にも成功し、低温ではπ-d相互作用に基づく明確な物性の差が現れることを見出した。 新規π-d(f)系の開拓:ピリミジン-TTF-M系(π-d系)を構築し、常磁性半導体が見いだされた。いくつかの4f-3d系単分子磁石を開発し、4f-3d間交換相互作用、量子トンネル効果の機構を明らかにした。天然有機分子の電子ドナー性を見出し、その電荷移動錯体、遷移金属錯体における電導性や磁性を評価した。希土類錯イオンを対アニオンとするイオンラジカル塩の電導性、単分子磁石性能を評価した。ラジカル-コバルト系(π-d系)単一次元鎖磁石から世界最高の保磁力(52kOe)を有する「硬い」磁性材料を開発した。 光照射を利用した電荷移動錯体の電気特性の制御:DCNQI銀塩を対象に、単結晶のデバイス化を目指し、接合子構造となる、局所的に伝導性が異なる“単結晶"への変換を試み、特異な光応答についての知見を得た。, 15073101
2003 - 2007 - 超分子アーキテクチャ－を利用した複合機能性分子磁性材料の開発
2004 - 2006 - Synthesis, Structures, Physical Properties, and Functions of Magnetic Materials
NOGAMI Takashi; ISHIDA Takayuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), Supramolecular techniques such as host-guest complex formation have been used to tune molecule-based magnetic materials. We have developed several magnetic materials possessing nano-sized pores or cavities, whose magnetic properties were changed by inclusion of small diamagnetic molecules. Some magnetic materials exhibited photo-induced magnetism. We also developed single-molecule magnets containing 3d-and 4f-metal ions. Several results from this project are listed below : 1)Weak ferromagnet possessing a chiral lattice was prepared and their magnetic structure was characterized by means of polarized neutron diffraction study. 2)Photo-induced magnetism was found in [M(pm)(N_3)_2](M=Mn,Fe,Co,Ni). 3)Diamagnetic-ion inclusion was applied for the magnetic coupling switch in the nickel(II) complex having a polyether side-arm. 4)Crown-ether spin label reagents were developed. 5)Honeycomb-like porous compound [Cu(4APM)(OCH_3)(NO_3)] was prepared and the crystal structure was solved in a relatively rare space group R-3. 6)The high-spin ground state was characterized for the hybrid metal-radical solid [Ni(4ImNNH)_2(NO_3)_2]. 7)The lanthanide-containing complexes [DyCuDy],[Dy_4Cu], and [Tb_4Cu] behaved as single-molecule magnets., 15550115
2003 - 2004 - 磁気応答型イオンセンサーの開発
石田 尚行
(財)材料科学研究助成基金, 研究助成, Principal investigator
2003 - 2004 - 分子磁性の超分子的制御
2001 - 2003 - 高い磁気転移温度をもつ分子性強磁性体の開発
野上 隆; 石田 尚行; 岩崎 不二子
日本学術振興会, 科学研究費助成事業, 電気通信大学, 特定領域研究(B), メタ配位子であるピリミジン(PM)とV(IV)Oとの錯体の構造を磁性を調べた。その結果、V(IV)の磁性軌道であるt_<2g>とPMのπ軌道との共役により、スピン分極機構でメタ位のV(IV)スピン間に強磁性的相互作用が働くことがわかった。4位にニトロニルニトロキシドを結合させたPMとCuX_2(X=Cl,Br)との錯体は6角形の6量体を形成し、直径11Å程度の空洞を作る。この空洞に種々の分子を導入すると、水素結合により空洞方向の強磁性的相互作用が強まることを見つけた。4,6-ジメチルPMとCuBr_2との錯体ではらせん構造が形成され、単結晶ではキラルな構造を示す。磁性は1次元反強磁性鎖モデルで解析できる。PM誘導体やピラジン誘導体とMn(II), Co(II), Ni(II)との錯体の構造と磁性の関係を調べた。これらの系ではσ結合を介した反強磁性的相互作用とπ結合を介した強磁性的相互作用が共存し、後者の寄与のほうが大きかった。PM-M[N(CN)_2]_2-G型錯体(M=Fe(II), Co(II) ; G=各種脂肪族アルコール)は、10K以下で弱強磁性体転移を示した。最小のラジカル配位子であるイミノニトロキシド(IN)とCu(II), Cd(II)との錯体の合成に成功し、磁性と構造との関係を調べた。Cd錯体は2量化により700K以上の強い反強磁性的相互作用を示した。TEMPO系有機ラジカル強磁性体のμSR,比熱測定から磁気的相互作用を明らかにした。スピロ結合で結ばれたアクリジンジニトロキシドの合成に成功し、構造と磁性を調べた。メタ位にINを有するジラジカル分子の基底状態は、第3の置換基の種類によって1重項にも3重項にもなりうることを見つけた。導電性錯体を与える新規ドナー分子を目指して、分子内に酸素とセレンを有するフルバレン誘導体の合成に成功した。, 11224204
1999 - 2001 - 安定な芳香族置換ニトロキシド類を用いた高Tc磁性体や磁性導体の開発
石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 特定領域研究(A), 本研究は、高い転移温度を有する分子性磁性体や、磁性と関連した複合材料の開発が主眼である。芳香族置換基を有するニトロキシドラジカルを、有機ラジカル系強磁性体の構築のために用いた。また、複素芳香族置換基を遷移金属錯体の配位子として用いた。 純粋な有機化合物からなる磁性体の構築のために、ジフェニルニトロキシドラジカル類の磁性体への応用を検討したところ、分子間で強磁性的相互作用を与える系が比較的多いことがわかった。そのような背景からスピロビアクリジン-N,N'-ジオキシルを設計し、合成した。 ピリミジン架橋(PM)を用いた錯体の分子性磁性体の開発を進めた。アニオンにも磁気カップラーとして機能させる目的で、π共役系1価アニオンであるN(CN)_2^-を導入した。PM・M[N(CN)_2]_2(M=Fe,Co,Ni)の結晶構造は同形であり、磁気測定によれば、転移温度はそれぞれ3.2,1.8,8.4Kであった。前の二者は弱強磁性挙動を示した。 ラジカル置換基としてニトロニルニトロキシド(NN)を選び、それを4位あるいは5位に有するPM架橋の利用を検討した。[4PMNN・CuX_2]_6(X=Cl,Br)は、12スピン系大員環状の分子構造を有し、結晶中ではカラムを形成する。チューブ状空間にゲスト分子を取り込ませたところ、強磁性的相互作用が増大した。すなわち、分子磁性をホスト-ゲスト化学などにより超分子的に制御する可能性が示された。複素環としてピラジンを用いたもののなかにも、磁気的に興味深い物質が得られた。, 12020219
2000 - 2000 - 高い磁気的転移温度をもつ共役有機ラジカル系とその遷移金属錯体の開発
2000 - 2000 - パイ共役架橋配位子の利用に基づく分子性強磁性金属を目指した遷移金属錯体の開発
1999 - 1999 - 高い強磁性体転移温度をもつ共役有機ラジカル系の開発
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 特定領域研究(A), 1 π共役有機NOラジカルの分子間強磁性的相互作用 各種π共役安定有機NOラジカルを合成し、磁気測定を行った結果、強磁性的相互作用を示す系をいくつか見つけた。π共役骨格としてはアクリジン、フェナンスレン、ベンズイミダゾール等を用いた。結晶構造解析結果をもとに強磁性的相互作用の原因を調べた結果、2種類の相互作用を見つけた。1つはMcConnellモデルによるものであり、π電子系の重なりでは、分子間で最近接原子同士は反平行のスピンを誘起しあうという原理に基づく。もう1つは、ある分子のSOMOが隣原子のSOMOと直交していることに基づく。またアルキル基を有するビス(ジフェニル)ニトロキシドは、アルキル基が長くなるにつれて強磁性的相互作用が強くなった。分子間アルキル鎖同士のファスナー効果が原因と思われる。 2 TEMPO系強磁性体の強磁性的相互作用 TEMPO系強磁性体ではNOラジカル部位は2次元ジグザグ面を形成し、面内の磁気的相互作用は既に解明された。面間相互作用に関して、偏極中性子回折およびμSR測定などから、面間に存在するフェニル環同士の重なりによる磁気的相互作用の伝達経路を明らかにした。 3 ピリミジン・遷移金属錯体の磁性 メタ配位子であるピリミジン(PM)とCu(II)、Co(II)などの錯体を各種合成し、構造と磁性の関係を調べた。その結果、PMの2つの窒素上での配位が、axial/equatorial配位の時は強磁性的相互作用が、equatorial/equatorial配位の時は反強磁性的相互作用が働くことを明らかにした。これは隣同士の磁性軌道が重なりをもつか直交するかに起因する。また、PM_2CoX_2(X=Cl,Br)はキラルな結晶構造をもち、5Kで弱強磁性体に転移した。, 10146217
1998 - 1998 - 安定有機ラジカルや遷移金属錯体を用いた分子性強磁性体の開発に関する研究
1997 - 1998 - 安定有機ラジカルを用いた分子性強磁性体の開発に関する研究
1996 - 1996 - 多数の硫黄原子を有するTTF誘導体の合成と錯体の電導性
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, 4、5-メチレンジチオ-4'、5'-(2-オキサトリメチレンジチオ)TTF(略してMOTT)錯体を電解結晶法で合成し、電気伝導度の温度変化を測定した。その結果、XF_6塩(X=P、As、Sb、Nb、Ta)で金属伝導性を示したが、すべての系で22-45Kの範囲で半導体に転移した。(MOTT)_2AsF_6錯体の伝導度の圧力効果を測定した結果、低温部での金属・半導体転移は6kbarの圧力で完全に消失したが、超伝導は観測されなかった。金属・半導体転移はこれらの錯体の低次元性に由来すると思われるが、このことは、錯体の結晶構造解析に基づいたバンド計算からも確かめられた。N、N-ジメチルアミノTTFはTTFよりも更に強いドナー分子であることが期待され、それを用いた錯体の伝導性や磁性に興味がもたれる。我々はリチオTTFに対する求電子反応でその分子の合成に成功した。BEDT-TTFのように、多数の硫黄原子を有するTTF誘導体を含む錯体は、2次元錯体を与え、超伝導に有利であることが知られている。そこで我々は、リチオTTF同士を求電子反応を用いて硫黄で橋渡しする簡便な方法を見つけた。従来の合成方法が多段階合成であるのに対して、本方法は1ポット合成である点に意義がある。従来の伝導性錯体のほとんどは、1、3-テトラチアフルバレンおよびその誘導体をベースにしている。1、2-テトラチアフルバレン(略して1、2-TTF)誘導体も興味あるドナー分子である。我々はジベンゾ-1、2-TTFとBEDT-1、2-TTFの合成を試み、成功には至っていないが、1、2-ジチオール環をアジン結合で結んだ新規物質の合成に至っている。, 07232217
1995 - 1995 - フラーレンの化学反応と電子材料への応用
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, 4、5-ジメトキシベンザインとC60との{2+2}環化付加体の結晶構造解析に成功した・フラーレン{2+2}付加体の結晶構造解析では最初の例である。C60の付加部分でのC-C結合が、1.645Åと異常に長い等の興味深い知見が得られた。安定ラジカルとして有名なTEMPOラジカルをC60に付加させた分子を合成した。この分子は分子性磁性体としても、フラーレンを有するスピンラベル分子としても興味が持たれる。SQUID測定から、この分子自体は弱い反強磁性相互作用を示すことがわかった。電子写真の分野における電子輸送剤として、C60に各種ジアルキルカルベン1分子が付加した物質の電子輸送能を検討した。これらはC60の5、6付加体を6、6付加体の混合物である。C60分子中にアルキル基を導入することで、基盤ポリマーへの相溶性が向上した。Time of Flight法による電子移動度の測定から、電子移動度が大きいことで注目されているC60よりも、1.6倍程度大きい電子移動度をもつ物質も見つけた。優れた電子輸送剤は、有害なオゾンの発生を伴わない電子写真の開発を可能ならしめるので、各方面から切望されている。クロロベンゼン中、アンモニア水存在下でC60と脂肪族アルデヒド、およびベンジルアルデヒドとの反応を調べた。その結果、前者では、マススペクトル、2次元NMR、元素分析等から、C60の6、6位で2、5-ジアルキルシクロブチルアミン環を形成する生成物を与えることがわかった。後者では、C60の6、6位で、ベンジル基と水素がラジカル付加したと思われる生成物を与えた。これらの反応はC60の新規反応として興味がもたれ、将来のC60を用いた新素材開発にとって有用であると思われる。, 07213211
1995 - 1995 - 分子間強磁性的相互作用の発現および有機強磁性体の開発に関する研究
1995 - 1995 - 高スピン有機分子とそれを用いた分子系、及び有機強磁性体の開発
石田 尚行
西田記念基礎有機化学研究助成基金, 研究助成, Principal investigator
1994 - 1995 - 多数の硫黄原子を有するTTF誘導体の合成と錯体の電導性
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, メチレンジチオ(2-オキサトリメチレンジチオ)テトラチアフルバレンを成分とするイオンラジカル塩結晶を電気化学的方法で合成した。錯体中のアニオン部には、種々の無機の直線アニオン、正八面体アニオン、正四面体アニオンを用いた。直線アニオンおよび正四面体アニオンの場合は半導体であった。八面体アニオンPF_6^-、AsF_6^-、SbF_6^-、NbF_6^-、TaF_6^-の場合はすべて、高温部で金属的挙動を示し、低温部(22-68K)で非金属に転移した。PF_6^-とAsF_6^-塩の結晶構造は、共にβ型であった。Extended Huckel分子軌道をベースにした強結合近似によるバンド計算では、擬一次元的なフェルミ面を与えた。圧力をかけた状態での伝導度の温度変化を測定するため、圧力セルを作製した。AsF_6^-塩では、7.9kbarの圧力下では上記の非金属転移は抑えられて、2.5Kまで金属状態を維持した。また、これらの実験結果を以前我々が行なった類似ドナー分子、エチレンジチオ(2-オキサトリメチレンジチオ)テトラチアフルバレンのイオンラジカル塩の伝導性と比較した。多数の硫黄原子を有する新規ドナー分子をめざして、ビス(エチレンジチオ)チエノチオフェンとビス(エチレンジチオ)チエノジチインを合成した。1分子中に、前者は6個の、また後者は7個の硫黄原子を有する。それらの分子構造をX線結晶構造解析により決定した。導伝性錯体の開発をめざして、TCNQとDCNQIの部分構造をあわせ持ったアクセプター分子であるN、7、7-トリシアノキノメタンイミンの合成法を確立した。, 06243213
1994 - 1994 - フラーレンの化学反応と電子材料への応用
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, C_<60>の付加反応を調べた。C_<60>とメタクロロ過安息香酸との反応で、C_<60>に酸素原子が付加することを見いだした。酸素2付加体を単離し、その^<13>C-NMRスペクトルから、生成物はCs対称性をもつことを明らかにした。これには3つの候補がある。C_<60>とo-ジメトキシベンザインとの1:1付加体の単結晶を作成し、結晶構造解析を行なった。ベンザインはC_<60>の6員環・6員環縮合部分に付加して、シクロブタン環を形成することを証明した。付加したC_<60>部分のC-C結合距離は1.645Åと異常に長いことがわかった。この研究はC_<60>の2+2環化付加反応生成物の結晶構造解析の最初の成功例である。C_<60>誘導体のスピンラベル分子としての応用、あるいは磁性への展開を念頭に置いて、C_<60>に2、2、6、6-テトラメチルピペリジン-1-オキシルラジカル(TEMPO)が付加した分子を合成した。1:1付加体をマルチ付加体から単離し、各種スペクトルから推定した結果、この分子はC_<60>の5員環・6員環縮合部分に付加し、もとの結合は開いていることがわかった。この分子のCVを測定した結果、還元電位はC_<60>にほぼ近く、C_<60>部分の共役が維持されていることを示した。酸化電位はTEMPOそのものより若干大きく、C_<60>の電子吸引性によると思われる。C_<60>の各種ジハロカルベン1:1付加体を単離し、各種のマススペクトル(FAB、ESI、MALDI、LD)を測定した。フラグメンテーションはLD、FAB、MALDIの順番に大きかったが、ESI法では親イオンピークのみ観測された。LDMSではオリゴマー化がおこり、C_<2n>(2n=122〜132と184〜196)のシグナルが観測された。, 06224209
1994 - 1994 - 分子間強磁性的相互作用の発現および有機強磁性体の開発に関する研究
1994 - 1994 - フラーレンの化学反応と電子材料への応用
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, C_<60>の化学を明らかにする研究の一環として、種々の反応試薬との反応を行ない、生成物の単離、スペクトルによる同定を行なった。C_<60>の反応性を明らかにすると同時に、付加体の構造と反応機構、付加体の反応性と官能基変換、および電気化学的な性質などを調べた。 具体的には、我々はまず種々のジエン試薬との付加体を単離し、構造を明らかにした。特にC_<60>のアントラセン二分子付加体が両極より付加した構造を持つことを^<13>CNMRより明らかにすることができた。これは二分子付加体の構造を決めた初めての例である。また、過酸酸化によるジオキシドC_<60>O_2も位置選択性の高い生成物であることが解かった。さらに、我々は“真の"カルベン、ニトレン付加を行なった。即ち、形式的にはカルベンやニトレン付加に相当する付加体が、ジアゾ、アジド化合物との反応により開いた構造をもつ付加体として得られるとの報告があるのに対し、我々の行なった直接的なカルベンやニトレン付加では閉じた6員環-6員環接合部における付加体を与えた。ジクロロカルベン付加体からの官能基変換を検討したが、求核試薬はC_<60>部分にも攻撃するためかなり困難であった。ナイトレン付加により得られたフラーレンアジリジンは新規骨格である。この類縁体はアジド蟻酸エステルを用いても得られた。アジリジン類は熱的に安定であり、閉じた6員環-6員環接合部位の付加体は安定な異性体と考えられる。アジリジン類の還元電位を調べたところ、窒素上の置換基によりかなり影響を受けることが解かった。温度を変えた^<13>CNMR測定により、このアジリジン骨格には窒素の反転が観察され、この反転のエネルギー障壁も窒素上の置換基にかなり左右されることが解かった。, 05233213
1993 - 1993 - 高スピン有機分子、有機強磁性体の開発
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, 平成五年度の最も注目すべき成果として、完全に有機物よりなる強磁性体を3種、錯体よりなる分子性強磁性体を2種見い出したことが挙げられる。特に、単一の有機ラジカル結晶の強磁性体は従来2種が知られているのみであったが、本研究で見い出された物質は史上第三、四、五番目のものである。 我々は芳香族環とアゾメチンで結合したTEMPOラジカル誘導体で、強磁性的相互作用を有するものを見出した。測定を行なった21種のTEMPO誘導体類のうち7種が強磁性的相互作用を示したが、この誘導体の系は従来の常識に反してその性質を示す確率が極めて高い。それらのヘリウム希釈冷凍機の温度領域での交流磁化率、磁化曲線の測定を行なった。その結果、芳香族としてフェニル、ビフェニル、p-クロロフェニルのものがそれぞれ0.18,0.4,0.4Kで強磁性転移を起こし、2-ナフチルのものが0.12Kで反強磁性転移を起こすことが解かった。また、幾つかのものについては室温におけるX線結晶構造解析を行なった。前二者の構造解析によれば、このN-O部分は二次元ネットワークを形成している。 別のアプローチとして、スピン源として遷移金属イオンを用い芳香族環としてピリミジンで架橋配位させ、d軌道上のスピンを平行にすることを試みた。ピリミジン誘導体を架橋配位子とするバナジルニ核錯体は、全ての場合に分子内強磁性的相互作用を示した、つまり基底三重項であった。分子内における交換パラメーターは1.1〜2.7Kであった。無置換配位子の場合は、分子間においても強磁性的相互作用が働いており、これは140mKで強磁性体に相転移することが解かった。分子間の強磁性的相互作用はキナゾリンの銅錯体でも見られ、これも極低温の測定により強磁性体転移することが解かった。, 05226213
1993 - 1993 - 新規な高スピン有機分子と、分子間強磁性的相互作用の発現に関する研究
1993 - 1993 - 高スピン有機分子,有機強磁性体の開発
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, TEMPOラジカルとアゾメチン結合で結合した各種芳香族化合物を合成し、磁化率の温度変化を測定した。その中で、芳香族化合物部がピレン、ナフタリン、ベンゼンの系でワイス温度がそれぞれ、0.7K、0.5K、0.73Kの強磁性的相互作用を示した。ナフタリンの系では4.2Kと1.7Kで磁化の磁場強度依存性を調べ、低温ほどスピン量子数が大きくなることが判った。この系では更に0.45Kまで交流磁化率を測定したが、磁気モーメントは温度低下に伴って急激に増加する一方で、これよりも低温度で強磁性体になることが期待される。芳香族化合物部分がピレンの系では、反強磁性的相互作用も共存した。また、これらのラジカル化合物とDDQやトリアミノベンゼン誘導体とのCT錯体を合成したが、いずれも常磁性体であった。芳香環のメタ位に結合したラジカル間には強磁性的相互作用が働くのに対し、オルトまたはパラ位に結合したラジカル間には反強磁性的相互作用が働く。この規則がスピン源に遷移金属を用いた時に成り立つか否かを確かめるため、ピリミジン、あるいはピラジン誘導体を配位子として用い、これと遷移金属ヘキサフルオロアセチルアセトナートとの2核錯体を各種合成したが、いずれも反強磁性的相互作用を示した。安定ラジカルと結合したドナーまたはアクセプター分子を成分とするCT錯体が強磁性的相互作用を示す可能性があるとの我々が提出したモデルに基ずき、TTFにニトロキシドラジカルが2個π共役で結合した分子の合成に成功し、ESRスペクトルがジラジカル構造を確認した。また、C_3対称性を有する安定な基底三重項分子の合成を目指して、トリフェニルメタン型分子にニトロキシドラジカルが2個結合した分子を合成し、ESRスペクトルでジラジカル構造を確認した。, 04242208
1992 - 1992 - 機能性有機電子材料の合成と物性,構造
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, TEMPOラジカルとアゾメチン結合で結合した各種芳香族化合物を合成し、磁化率の温度変化を測定した。その中で、芳香族化合物部分がピレン、ナフタリン、ベンゼンの系でワイス温度がそれぞれ、0.7K、0.5K、0.73Kの強磁性的相互作用を示した。ナフタリンの系では4.2Kと1.7Kで磁化の磁場強度依存性を調べ、低温ほどスピン量子数が大きくなることが判った。この系では更に0.45Kまで交流磁化率を測定したが、磁気モーメントは温度低下に伴った急激に増加する一方で、これよりも低温部で強磁性体になることが期待される。ピリミジン、あるいはピラジン誘導体を配位子として用い、これと遷移金属2核錯体を各種合成したが、いずれも反強磁性的相互作用を示した。TTFにニトロキシドラジカルが2個π共役で結合した分子の合成に成功し、ESRスペクトルでジラジカル構造を確認した。また安定な基底三重項分子の合成を目指して、トリフェニルメタン型分子にニトロキシドラジカルが2個結合した分子を合成し、ESRスペクトルでジラジカル構造を確認した。C_<60>とベンザイン、各種ジエンが付加反応することを見いだした。生成物をHPLCで分離し、NMR、マススペクトルで同定した。また、C_<60>に対するジクロルカルベンの付加反応、mCPBAによる酸素付加反応も検討した。半導体レーザーの倍波発生用を目指して、エチレンの4個の水素をドナーおよびアクセプター性置換基で置換した分子や、2個の芳香環がΛ型に結合した分子を各種合成し、粉末法によるSHG測定、EFISH法によるβ値を測定した。その結果、青色領域に透明なSHG活性物質をいくつか見いだし、それらの結晶構造解析も行った。多数の硫黄原子を有する新規ドナー分子を目指して、1分子中に6個および7個の硫黄を有する多環共役分子の合成に成功し、結晶構造解析を行った。, 04205050
1992 - 1992 - 機能性有機電子材料の合成と物性,構造
野上 隆; 石田 尚行
日本学術振興会, 科学研究費助成事業, 電気通信大学, 重点領域研究, 次の3つのテ-マについて研究した。1.高電導性有機錯体の合成と物性;2.有機非線形光学材料;3.有機磁性体。1については1分子中に多数の硫黄原子を有するTTF誘導体と,それを用いた電導性錯体の開発を行なった。この種の錯体は高温部で金属であっても,低温部で絶縁体に転移する系が多い。本研究でもその傾向が見られたが,BEDTーTTF_3Br_2とBEDTーTTFーC(CN)_3ーCu CN系が4.2Kまで金属状態を維持することを見い出した。前者については結晶構造解析を行なった。また4員環であるジチエテ同士が2重結合で結合した構造を基本骨格にもち,1分子中に6個の硫黄を有する略称BETを合成した。TTF系が7π系であるのに対して,BETは5π系の新しい型のドナ-分子である。2に関しては半導体レ-ザ-の倍波発生用の2次の非線形光学材料の合成を行った。エチレンは最小の共役系なので,この4つの水素をドナ-およびアクセプタ-置換基で置換えた物質系は,吸収端が短波長であり,当初の目的に有望であると考えた。一連の分子内電荷移動系の合成を行なった結果,4種類の系について青色透過性があり,宜つSHG活性であることを見い出した。またSHG活性の系については結晶造解析を行った。3については有機強磁性体を目指しているいくつかのアプロ-チから合成を行なった。ベンゼン環のメタ位に置換したカルベンの電子スピンは互いに平行であることを参考にして、ピリミジン骨格の窒素にスピン源である遷移金属が配位した錯体を合成した。C_<60>のLUMが3重に縮重しているため,LUMOに複数個の電子が入った系は高スピン状態になると考えられる。K^+ークリプタンド,あるいはK^+ー18ークラウンー6をカチオン部にもち,アニオン部がC_<60>である錯体を合体した。現在磁気的測定を定ないつつある。, 03205047
1991 - 1991 - Synthesis of New Organic Donor Molecules and Highly Conducting Organic Complexes
NOGAMI Takashi; ISHIDA Takayuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for General Scientific Research (C), (1)Highly Conducting Organic Complexes Crystal structure has a pronounced effect on the electrical properties of conducting organic salts. In order to investigate the effect of the slight modification of the donor site on the crystal and band electronic structures and electrical conductivities, we compared the crystal and band electronic structures of BEDT-TTF_2PF_6, EVT_2PF_6, and VT_2PF_6. We found that the replacement of the two ethylene groups of BEDT-TTF by vinylene group results in the change from two-dimensional band structure of BEDT-TTF salt to pseudo one-dimensional band structure of VT salt. In order to obtain new conducting organic salts, we synthesized several transition metal-dmio salts and TTF derivatives possesing sulti-sulfur. atons in the soJLecule. We also synthesized conducting salts containing the latter TTF derivatives by an electrochemical method. Some of the EOTT salts exhibited. metallic conductivities down to 4.2 K. (2)Non-Linear Optical Materials Crystallographic analysis was made for the seeond-order non-linear optical material possessing 1, 3-dithiole ring as a donor site and eyano and ester groups as the acceptor sites. We also found several SHG active materials for the ethylene derivatives, in which four, hydrogen atoms were su4stituted by dqw and acceptor substituents. These materials are transparent inLt#e, blue y#veleaft rwon, and can be used as frequency doublers of infrared semiconductor lasers., 02640344
1990 - 1991
