KUWAHARA DAISUKE
| Coordinated Center for UEC Research Facilities | Associate Professor |
| Department of Engineering Science | Associate Professor |
| Cluster III (Fundamental Science and Engineering) | Associate Professor |
Researcher Information
Research Activity Information
Paper
- Elucidation of solid particle interfacial Phenomena in liquid sodium: Magnetic interactions on liquid metal and solid atoms at the solid interface
Chikai Tei; Masahiko Ohtaka; Daisuke Kuwahara
Last, Chemical Physics Letters, Elsevier BV, 829, 140755-140755, Oct. 2023, Peer-reviwed
Scientific journal - DFT Calculations of Changes in NMR Chemical Shifts in Aqueous Solutions of Heavy-Metal Nitrates
Y. Asakura; D. Kuwahara; N. nakagawa
Last, J. Comput. Chem. Jpn. Int. Ed., Society of computer chemistry, Japan, DOI: 10.2477/jccjie.2021-0048., Apr. 2022, Peer-reviwed
Scientific journal, English - Average intermolecular distances and dynamics of ruthenium-containing organometallic ionic liquids studied by nuclear overhauser effects between 19F and 1H Nuclei and NMR relaxation rate measurements
Chikai Tei; Daisuke Kuwahara; Tomomi Higashi; Tomoyuki Mochida
Last, Bulletin of the Chemical Society of Japan, Chemical Society of Japan, 91, 4, 571-576, 2018, Peer-reviwed, The physical properties of organometallic ionic liquids containing cationic ruthenium sandwich complexes {[Ru(C5H5)-(C6H5R)]X
R = OCH(C4H9)2, OCH(C2H5)(C6H13)
X = N(SO2CF3)2, N(SO2F)2} are dependent on the substituents. To obtain detailed information about the motional states and configurations of the constituent ions of these ionic liquids, we performed one-dimensional (1D) heteronuclear Overhauser enhancement spectroscopy (HOESY) NMR experiments and the standard relaxation rate (1/T1 and 1/T2) measurements. We determined the intermolecular cross-relaxation rates between some cation blocks and the anion in each ionic liquid by analyzing the experimental data based on the extended Solomon differential equations. As a result, we were able to estimate several intermolecular distances between the cations and anions in the ionic liquids. This is the first time that NMR has been applied to the determination of the intermolecular crossrelaxation rates and the estimation of intermolecular distances of highly viscous ionic liquids consisting of heteronuclear multiple-spin systems without the support of any X-ray data. The viscosities of these ionic liquids depended largely on the motional correlation times of the cations rather than on the intermolecular distances between the cations and anions.
Scientific journal, English - Dynamics and configuration in new ruthenium-containing ionic liquids by NOE cross-relaxation NMR
Chikai Tei; Tomoyuki Mochida; Daisuku Kuwahara
Last, Proceedings of 58th Experimental Nuclear Magnetic Resonance Conference, 74-74, 26 Mar. 2017, Peer-reviwed
International conference proceedings, English - Theoretical study of a simple rotational-echo double-resonance NMR for homonuclear spin-1/2 pairs
Daisuke Kuwahara; Takahiro Sakuragi; Chikai Tei
Lead, MAGNETIC RESONANCE IN CHEMISTRY, WILEY-BLACKWELL, 54, 2, 108-118, Feb. 2016, Peer-reviwed, We investigate theoretically intriguing aspects of a simple rotational-echo double-resonance (REDOR) NMR technique for homonuclear spin-1/2 pairs undergoingMAS. The simple technique sets Gaussian soft p pulses at every halfMAS rotational period in the pulse sequence. The reduction in rotational echo amplitude (the REDOR echo reduction) is observed at the end of the evolution period t(e) = (n+1) T-r, where T-r is aMAS rotational period. The exact average Hamiltonians for the homonuclear REDOR (hm-REDOR) technique are calculated by dividing the evolution period into four periods. We show theoretically and experimentally that the hm-REDOR technique produces the REDOR echo reductions for homonuclear spin-1/2 pairs. In addition, the theoretical results reveal that the REDOR echo reductions are independent of the chemical-shift difference, delta, under a simple condition of kappa = delta/omega(r)>= 6 and t(e)< 10 . (1/d'), where omega r is the sample spinning frequency and d' is the dipolar coupling constant expressed in Hz. We call this simple condition the master condition. This means that the REDOR echo reductions for a homonuclear spin-1/2 pair can be calculated under the master condition by considering only d' and omega(r), which is the case for a heteronuclear spin pair. Finally, we demonstrate that four-phase cycling yields the multiple-quantum filtered hm-REDOR experiment, where the appearance of the REDOR echo reductions shows that the echo reductions are definitely attributable to the homonuclear dipolar interaction even if there is a slight unwanted effect from the recovered chemical-shift anisotropy in these reductions. Copyright (C) 2015 JohnWiley & Sons, Ltd.
Scientific journal, English - Crystal Structures and Phase-Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion
Tomoyuki Mochida; Yusuke Funasako; Takeshi Inagaki; Meng-Jiao Li; Kotaro Asahara; Daisuke Kuwahara
Chem. Eur. J., Wiley, 19, 20, 6257 – 6264-6508, Apr. 2013, Peer-reviwed
Scientific journal, English - Phase transitions and thermal properties of decamethylferrocenium salts with perfluoroalkyl-sulfonate and -carboxylate anions exhibiting disorder
Shota Hamada; Yusuke Funasako; Tomoyuki Mochida; Daisuke Kuwahara; Kenji Yoza
Journal of Organometallic Chemistry, 713, 35-41, Jun. 2012, Peer-reviwed
Scientific journal, English - Ionic Liquids of Cationic Sandwich Complexes
Takashi Inagaki; Tomoyuki Mochida; Masashi Takahashi; Chikahide Kanadani; Toshiaki Saito; Daisuke Kuwahara
Chemistry, A European Journal, 18, 6795-6804, Mar. 2012, Peer-reviwed
Scientific journal, English - Nanocomposite Materials of Alternately Stacked C-60 Monolayer and Graphene
Makoto Ishikawa; Shu Kamiya; Shoji Yoshimoto; Masaru Suzuki; Daisuke Kuwahara; Naruo Sasaki; Kouji Miura
JOURNAL OF NANOMATERIALS, HINDAWI PUBLISHING CORPORATION, 2010, 891514, 2010, Peer-reviwed, We synthesized the novel nanocomposite consisting alternately of a stacked single graphene sheet and a C-60 monolayer by using the graphite intercalation technique in which alkylamine molecules help intercalate large C-60 molecules into the graphite. Moreover, it is found that the intercalated C-60 molecules can rotate in between single graphene sheets by using C-13 NMR measurements. This preparation method provides a general way for intercalating huge fullerene molecules into graphite, which will lead to promising materials with novel mechanical, physical, and electrical properties.
Scientific journal, English - Structural change around the phase transition in decamethyl-ferrocene acenaphthenequinone complex studied by high-resolution solid state NMR
Daisuke Kuwahara; Hideaki Nakamura; Tomoyuki Mochida
Lead, Proc. of the 50th Experimental Nuclear Magnetic Resonance Conference, 96, Mar. 2009, Peer-reviwed
International conference proceedings, English - High-resolution solid-state NMR investigation of the phase transition in decamethylferrocene-acenaphthenequinone charge-transfer complex
Hideaki Nakamura; Daisuke Kuwahara; Tomoyuki Mochida
Corresponding, Journal of Physical Chemistry A, 113, 48, 13601-13607, 2009, Peer-reviwed, A charge-transfer complex composed of decamethylferrocene (D) and acenaphthenequinone (A) was prepared. The material was a 1:1 neutral complex with a mixed-stack structure and exhibited a phase transition at-16 °C. High-resolution 13C and 1H NMR spectroscopy revealed that an inclination of A with respect to D occurs below the phase-transition temperature. The 1H spin-diffusion rates of the complex undergoing high-speed magic-angle spinning (MAS) were measured to determine the shortest 1H-1H distance r between D and A. To analyze the experimental results, we derived the analytical expression of the spin-diffusion rate Wz for a homonuclear multispin system undergoing MAS. It was found that Wz for the complex is proportionalonly to 1/r6 under high-speed MAS conditions. On the basis of this relationship and the crystal structure at 20 °C, it was determined that the shortest 1H-1H distance r at-27.7 °C (below the phase transition temperature) is 0.4 Å shorter than that at 20 °C. Given this information, a plausible model of the low-temperature structure is discussed. © 2009 American Chemical Society.
Scientific journal, English - High-resolution NMR spectra of n-alkanes penetrating into carbon fibers and of protons in carbon fibers
Yuya Yamazaki; Nobuaki Kobayashi; Kunio Nikki; Daisuke Kuwahara
MAGNETIC RESONANCE IN CHEMISTRY, JOHN WILEY & SONS LTD, 46, 8, 730-733, Aug. 2008, Peer-reviwed, We present a simple NMR method for microscopically exploring the local environment in carbon fibers. The method utilizes n-alkanes as probe molecules, where the n-alkanes penetrate carbon fibers of interest. The high-resolution H-1 NMR spectra for a mixture of a carbon fiber and n-alkanes acquired by this method show a shift of the resonance line, which is due to the local structure of the fiber. The utility of this method is discussed on the basis of the H-1 NMR spectra obtained. In addition, the H-1 distribution and the local motion in the structure of the carbon fiber are revealed in view of the H-1 NMR spectra. Copyright (C) 2008 John Wiley & Sons, Ltd.
Scientific journal, English - Ferrocenylpyrazole - A versatile building block for hydrogen-bonded organometallic supramolecular assemblies
Tomoyuki Mochida; Fumiko Shimizu; Hirotaka Shimizu; Kazuya Okazawa; Fuminori Sato; Daisuke Kuwahara
JOURNAL OF ORGANOMETALLIC CHEMISTRY, ELSEVIER SCIENCE SA, 692, 9, 1834-1844, Apr. 2007, Peer-reviwed, The crystal architectures of 5-ferrocenylpyrazole (1) and its metal complexes were investigated. Compound I can form non-solvated and chloroform-solvated crystals. In both cases, I forms a zigzag one-dimensional architecture via (NHN)-N-... hydrogen bonds. The hydrogen bond exhibits a twofold disorder, which was shown to be static by solid-state C-13 NMR. In the solvated crystal, the chloroform is released at 415 K, associated with melting of the crystal. The reaction of 1 with metal salts provided metal-centered ferrocenyl clusters [Zn(NO3)(2)(1)(4)] (4), [Co(NO3)(2)(1)(4)] (5), [COCl2(1)(4)] (6), [Zn(NCS)(2)(1)(2)] (7), cis-[Pt(NH3)(2)(1)(2)](PF6)(2) (8), and trans- [Pt(NH3)(2)(1)(4)](PF6)(2) (9). In all of these complexes, I acts as a monodentate ligand. In 4, 5, and 7, the multinuclear units are joined via hydrogen bonds to form supramolecular chains. Two polymorphs were found for the crystals of 4. Both are composed of the same hydrogen-bonded chains, but their arrangements are different. 5-Ferrocenyl-1-tritylpyrazole (2) and 4-ferrocenyl-1-methylpyrazole (3) were also crystallographically characterized. (c) 2006 Elsevier B.V. All rights reserved.
Scientific journal, English - Dynamics of 9-hydroxyphenalenone studied by one-dimensional solid-state spin exchange NMR
Daisuke Kuwahara; Hiroyuki Koyano; Taisuke Manaka; Hideaki Nakamura; Tomoyuki Mochida; Tadashi Sugawara
JOURNAL OF PHYSICAL CHEMISTRY A, AMER CHEMICAL SOC, 110, 51, 13731-13735, Dec. 2006, Peer-reviwed, We present a new NMR method to clarify the dynamics of proton tautomerism in solid 9-hydroxyphenalenone. Two C-13 resonance lines influenced by the proton tautomerism have a chemical-shift difference between them, which increases with decreasing temperature. To depict the precise potential curve of the proton tautomerism, the chemical-shift difference when the proton tautomerism is completely frozen is necessary. For solid 9-hydroxyphenalenone and its derivatives, the freezing temperatures are often under -100 degrees C. When the freezing temperatures are below the temperature range in which standard magic angle spinning NMR probes can perform a sample spinning, it is very difficult to obtain the shift difference. The NMR experiments based on this new method are performed at a temperature significantly higher than -100 degrees C at which the proton tautomerism is still active. The new method yields the C-13 spin relaxation rates, the rates for the proton tautomerism, and the populations of the two tautomers. Using the populations and the C-13 chemical-shift difference at that temperature, we determined the chemical-shift difference at the freezing temperature. We also obtained several parameters characterizing the potential profile for the proton dynamics in solid 9-hydroxyphenalenone.
Scientific journal, English - Erratum: Feasibility of the overtone NMR for half-integer quadrupolar nuclei (Chemical Physics Letters (2005) 414 (514))
Daisuke Kuwahara; Hajime Okamoto; Yuya Yamazaki
Chemical Physics Letters, 416, 4-6, 386, 16 Dec. 2005, Peer-reviwed
Scientific journal, English - Research of the tautomerism for 9-hydroxyphenalenone derivatives by the solid-state exchange NMR
Hiroyuki Koyano; Taisuke Manaka; Daisuke Kuwahara; Tomoyuki Mochida
Proceedings of The 1st Asia-Pacific NMR Symposium, 224, Nov. 2005, Peer-reviwed
International conference proceedings, English - Is it possible to directly detect the overtone NMR for half-integer quadrupolar nuclei?
Hajime Okamoto; Yuya Yamazaki; Hiroki Nose; Daisuke Kuwahara
Proceedings of The 1st Asia-Pacific NMR Symposium, 4, Nov. 2005, Peer-reviwed
International conference proceedings, English - Feasibility of the overtone NMR for half-integer quadrupolar spins
Daisuke Kuwahara; Hajime Okamoto; Yuya Yamazaki
Chemical Physics Letters, 414, 514-519, Sep. 2005, Peer-reviwed
Scientific journal, English - Solid-state H-2 NMR study of phase transitions in deuterated crystals of 5-methyl-9-hydroxyphenalen-1-one and 5-bromo-9-hydroxyphenalen-1-one
T Mochida; D Kuwahara; S Miyajima; T Sugawara
JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 107, 44, 12315-12319, Nov. 2003, Peer-reviwed, The nature of the phase transitions and proton-deuteron dynamics in the crystals of 9-hydroxyphenalenone derivatives have been investigated by means of solid-state H-2 NMR spectroscopy. It was found that the antiferroelectric ordering of deuterons along the hydrogen bonds in 5-methyl-9-deuterioxyphenalenone (1-d) and 5-bromo-9-deuterioxyphenalenone (2-d) occurs below the phase transition temperatures at T-C = 44 K and T-I = 34 K, respectively. The microscopic origin of the incommensurate modulation in 2-d below T-I = 34 K is attributable to slight rotational displacements, which are fixed at commensurate angles below the lock-in transition at T-C = 22 K.
Scientific journal, English - Simulations of the C-13-N-14 REDOR NMR experiments performed with a frequency-sweep N-14 overtone pulse
D Kuwahara
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 377, 1-2, 20-26, Aug. 2003, Peer-reviwed, The author investigated the C-13-N-14 rotational echo double resonance (REDOR) NMR experiment performed with a frequency-sweep N-14 overtone pulse. The computer simulations of the experiment for powdered N-acetyl-D,L-valine were carried out. It was found from the simulations that, in a slow spinning region, C-13 diminished echo intensities remained invariant even when the center frequency of the frequency-sweep range was shifted a few tens of kHz. As a result, it became apparent that the REDOR experiment employing the frequency-sweep pulse had the adequate ability to determine the heteronuclear dipolar interaction for a C-13-N-14 spin system in solids. (C) 2003 Elsevier B.V. All rights reserved.
Scientific journal, English - Overtoneパルスを用いたREDOR信号の計算
桑原大介
第41回NMR討論会, 41, 414, 2002
Japanese - Real figure of two-dimensional spin-echo NMR spectra for a homonuclear two-spin system in rotating solids
D Kuwahara; T Nakai; J Ashida; S Miyajima
MOLECULAR PHYSICS, TAYLOR & FRANCIS LTD, 99, 11, 939-956, Jun. 2001, Peer-reviwed, Two-dimensional (2D) spin-echo NMR experiments have been carried out on polycrystalline [2,3-C-13(2)]-L-alanine under magic-angle sample spinning (MAS) conditions, so that two unusual resonance lines emerged along the F-1 axis (KUWAHARA, D., NAKAI, T., ASHIDA, J., and MIYAJIMA, S., 1999, Chem. Phys. Lett., 305, 35). To examine the spectral structure observed in the F-1 direction more closely the 2D NMR experiment was undertaken using a sufficiently small t(1) increment, yielding many more resonance lines on a spectrum sliced along the F-1 axis. The line distribution had a very unique and interesting structure. To elucidate the line positions theoretically, the signal for the 2D spin-echo experiment performed with any t(1) increment was calculated analytically for a homonuclear two-spin-1/2 system undergoing MAS. Virtually six resonance lines (exactly 12 resonance lines) occurred on a spectrum sliced along the F-1 axis. In addition, it was demonstrated that the intensities of some resonance lines were largely dependent on the dipolar interaction.
Scientific journal, English - Transient C-13-H-1 nuclear Overhauser effect in liquid crystal
H Fujimori; D Kuwahara; T Nakai; S Miyajima
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, PHYSICAL SOC JAPAN, 70, 4, 1117-1123, Apr. 2001, Peer-reviwed, Significant transient C-13-H-1 nuclear Overhauser effect (NOE) is observed in liquid crystal, and is explained by a local C-13-H-1 dipole-dipole interaction and relaxation. Solomon's classical two-pulse experiment gives a significant maximum in signal intensity of 2.5 times the equilibrium magnetization, and also gives a way of estimating zero-quantum transition probability for a dipole-coupled C-13-H-1 pair. The conventional inversion recovery sequence is recommended for the experimental determination of C-13 spin-lattice relaxation rates. Magnetization recovery after the Hartmann-Hahn signal enhancement deviates strongly from exponential behavior. Experimental data are shown for an antiferroelectric chiral smectic liquid crystal MHPOBC.
Scientific journal, English - Novel structure discovered on two-dimensional spin-echo NMR spectra for a homonuclear two-spin system in rotating solids
Daisuke Kuwahara; Toshihito Nakai; Jun Ashida; Seiichi Miyajima
14th Conference of the International Society of Magnetic Resonance, 130, 2001, Peer-reviwed
International conference proceedings, English - Novel satellites in a two-dimensional spin-echo NMR experiment for homonuclear dipole-coupled spins in rotating solids
D Kuwahara; T Nakai; J Ashida; S Miyajima
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 305, 1-2, 35-38, May 1999, Peer-reviwed, Additional resonance lines emerged along the F-1 axis on a two-dimensional (2D) NMR spectrum, when the 2D spin-echo pulse sequence was applied to a solid-state homonuclear two-spin system with a negligibly small J-coupling constant under magic-angle sample spinning. We found that the positions of the lines are determined by the sample spinning frequency and the difference of the isotropic chemical shifts. (C) 1999 Elsevier Science B.V. All rights reserved.
Scientific journal, English - Spin-echo experiments for homonuclear coupled spins under magic-angle sample spinning
Daisuke Kuwahara; Toshihito Nakai; Seiichi Miyajima
Proceedings of 40th Experimental Nuclear Magnetic Resonance Conference, 164, Feb. 1999, Peer-reviwed
International conference proceedings, English - Complete assignment of C-13 NMR spectra and determination of orientational order parameter for antiferroelectric liquid-crystalline MHPOBC
T Nakai; H Fujimori; D Kuwahara; S Miyajima
JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 103, 3, 417-425, Jan. 1999, Peer-reviwed, Complete assignment of the C-13 NMR lines is reported for both isotropic and oriented samples of antiferroelectric liquid-crystalline MHPOBC. Two-dimensional double-quantum coherence spectroscopy (2-D INADEQUATE) in the isotropic phase and field alignment-induced shifts (AIS) were studied. F-19-C-13 dipolar quartets were measured for TFMHPOBC, where a methyl group attached to the chiral center of MHPOBC is replaced by a trifluoromethyl group, to assist the assignment. Shielding tensor principal elements were determined for each carbon by site-separated spinning sideband spectroscopy (2-D TOSS-deTOSS). The orientational order parameter has been evaluated to be 0.73 at 403 K in the S-A phase using the experimentally determined AIS and the tensor elements and assuming an intramolecular free rotation model.
Scientific journal, English - NMR investigation of the oxyethylene unit ordering in some related dialkoxy laterally substituted nematogens
Rayssac, V; P Judeinstein; JP Bayle; D Kuwahara; H Ogata; S Miyajima
LIQUID CRYSTALS, TAYLOR & FRANCIS LTD, 25, 3, 427-436, Sep. 1998, Peer-reviwed, Laterally dialkylated nematogens containing a short terminal polyoxyethylene chain present a wide nematic range starting from room temperature. The ordering of the oxyethylene (OE) unit has been studied by C-13 NMR in the liquid crystalline phase. The values of the order parameters were derived from the transient oscillations observed during variable contact-time cross-polarization experiments. Along the oxyethylene chain, the order parameters decrease monotonically. These order parameter values do not present the usual odd-even effect and are noticeably smaller than those found for terminal alkoxy chains. Entering the nematic phase, the C-13 thermal evolution of the field-induced chemical shift in the OE unit is far smaller than the one usually observed for terminal alkyl or alkoxy chains, regardless of their non-negligible order parameters. In addition, no linear correlation between the order parameter and the field-induced chemical shift is observed for the carbons in the OE unit. This is an indication that the proportion between gauche- and trans-conformations in the OE unit is temperature dependent.
Scientific journal, English - Two-dimensional NMR measurements of heteronuclear dipolar powder spectra using the chemical-shift-anisotropy recovery technique
D Kuwahara; T Nakai; S Miyajima
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 291, 1-2, 244-248, Jul. 1998, Peer-reviwed, A novel and simple method for measuring heteronuclear dipolar spectra under magic-angle sample spinning is described; the present method utilizes a chemical-shift-anisotropy recovery technique exploited by Tycko, Dabbagh and Mirau in a two-dimensional NMR experimental scheme. The C-13-N-15 dipolar powder spectrum was obtained to give a internuclear distance for a doubly labeled l-alanine. The present method will be extended to observe a heteronuclear dipolar interaction between C-13 and quadrupolar nuclei having integer spins such as H-2 or N-14. (C) 1998 Elsevier Science B.V. All rights reserved.
Scientific journal, English - The applications of a magic-angle-turning technique for quadrupolar nuclei with half-integer spins
Daisuke Kuwahara; Toshihito Nakai
Proceedings of 38th Experimental Nuclear Magnetic Resonance Conference, 171, Mar. 1997, Peer-reviwed
International conference proceedings, English - Spinning-sideband suppression in DOR NMR spectra using a magic-angle-turning technique
D Kuwahara; T Nakai
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 260, 1-2, 249-252, Sep. 1996, Peer-reviwed, Spinning sidebands (SSBs) in double rotation NMR spectra for quadrupolar nuclei having half-odd-integer spins were suppressed using a two-dimensional (2D) NMR method based on a magic-angle-turning technique. The resultant 2D spectrum showed substantially no SSBs along one frequency axis whereas, along the other axis, conventional SSBs exhibited themselves.
Scientific journal, English - Spinning sideband summation for quadrupole MAS NMR spectra using a magic-angle turning technique
T Nakai; D Kuwahara
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 249, 3-4, 205-209, Feb. 1996, Peer-reviwed, Two-dimensional (2D) magic-angle spinning (MAS) NMR measurements for unravelling the overlapping spinning sidebands (SSBs) for quadrupolar nuclei having half-integer spins were reported; the method utilizes a magic-angle turning technique recently exploited for chemical-shift spectra. The projection of the resultant 2D spectrum reconstructs the inherent MAS lineshapes without SSBs, which can be straightforwardly analyzed to yield quadrupolar parameters. The SSB-free Na-23 MAS spectrum for Na2SO4, which would otherwise be observed under an infinite spinning speed, was obtained.
Scientific journal, English - SIMULATION OF HOMONUCLEAR 2-SPIN-1/2-SYSTEMS UNDER SAMPLE-SPINNING - EFFECTS OF JUMP MOTIONS ON NMR LINESHAPES
D KUWAHARA
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 231, 4-6, 414-420, Dec. 1994, Peer-reviwed, A method for the calculation of NMR lineshapes is presented for homonuclear two spin-1/2 systems performing jump motions in rotating solids. The NMR spectra of such spin systems were found to be useful for detecting the existence of conformational changes as well as that of molecular motions in the solid state spin systems.
Scientific journal, English - C-13 SOLID-STATE NMR-STUDY ON POPULATIONS, CONFORMATIONS, AND MOLECULAR MOTIONS OF GAMMA-VALEROLACTONE ENANTIOMERS ENCLATHRATED IN THE CHIRAL CHOLIC-ACID HOST
F IMASHIRO; D KUWAHARA; T TERAO
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2, ROYAL SOC CHEMISTRY, 10, 1759-1763, Oct. 1993, Peer-reviwed, C-13 Solid-state NMR spectra were measured for gamma-valerolactone in the cholic-acid host which exhibits efficient optical resolution. Both the more-favoured (S)-(-)-enantiomer [ (S)-1] and the less-favoured (R)-(+)-enantiomer [ (R)-1] of gamma-valerolactone were found to coexist microscopically in the cholic-acid channels by two-dimensional exchange NMR. Their populations were non-destructively determined from the intensities of their methyl-carbon signals. The principal values of the C-13 chemical-shift tensors for the methyl carbons were determined by the one-dimensional switching-angle sample spinning (1D-SASS) NMR method. By comparing the C-13 chemical-shift tensors with those calculated by the ab initio GIAO method, the conformation, of each enantiomer was determined as follows: (S)-1 has the methyl group in the equatorial direction to the five-membered ring of gamma-valerolactone, while (R)-1 has it in the axial direction. The optical resolution of gamma-valerolactone by the inclusion method using the cholic-acid host is mainly ascribed to the energy difference in the conformations of gamma-valerolactone. Temperature variation of the C-13 chemical-shift powder pattern for the methyl carbons of both enantiomers revealed the presence of an overall reorientation among a finite number of isotropically distributed sites accompanying slow rotational diffusion. The rate of the reorientation for (S)-1 is higher than that for (R)-1; moreover, the corresponding barrier for (S)-1 is notably lower than that for (R)-1.
Scientific journal, English - DYNAMICS OF FERROCENE MOLECULES ENCLATHRATED IN BETA-CYCLODEXTRIN AS STUDIED BY VARIABLE-TEMPERATURE ONE-DIMENSIONAL SASS (SWITCHING-ANGLE SAMPLE SPINNING) NMR-SPECTROSCOPY
D KUWAHARA; F IMASHIRO; T TERAO
CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 204, 5-6, 533-537, Mar. 1993, Peer-reviwed, The four guest ferrocene molecules in the unit cell of the beta-cyclodextrin/ferrocene inclusion compound crystal were found to have three different configurations among the five possible sites and exchange among the three; the enthalpy (DELTAH) and entropy (DELTAS) differences between two degenerate configurations and the other were obtained to be 4.8 +/- 2.5 kcal/mol and 19 +/- 9 eu, respectively.
Scientific journal, English - STUDY OF THE DYNAMICS OF FERROCENE ENCLATHRATED IN BETA-CYCLODEXTRINS AND GAMMA-CYCLODEXTRINS BY ONE-DIMENSIONAL SWITCHING-ANGLE SAMPLE SPINNING NMR-SPECTROSCOPY
F IMASHIRO; D KUWAHARA; N KITAZAKI; T TERAO
MAGNETIC RESONANCE IN CHEMISTRY, JOHN WILEY & SONS LTD, 30, 8, 796-797, Aug. 1992, Peer-reviwed, C-13 chemical shift powder patterns of ferrocene enclathrated in beta- and gamma-cyclodextrins were measured by one-dimensional switching-angle sample spinning NMR spectroscopy. The ferrocene molecules were found to precess with a precession angle of 69-degrees in gamma-cyclodextrin. In beta-cyclodextrin the ferrocene molecules I-III, in different motional states, were enclathrated with populations of 0.42, 0.32 and 0.26, respectively; ferrocene I is tightly enclathrated and rotates around its fivefold axis, whereas ferrocenes II and III precess with precession angles of 30-degrees and 42-degrees, respectively.
Scientific journal, English - DYNAMICS OF FERROCENE ENCLATHRATED IN DEOXYCHOLIC-ACID AS STUDIED BY SASS (SWITCHING-ANGLE SAMPLE SPINNING) NMR-SPECTROSCOPY
F IMASHIRO; N KITAZAKI; D KUWAHARA; T NAKAI; T TERAO
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 2, 85-86, Jan. 1991, Peer-reviwed, A C-13 chemical-shift powder pattern for ferrocene enclathrated in the deoxycholic acid channel selectively observed by SASS NMR reveals that the included ferrocene molecule is rotating around its five-fold axis; moreover, the axis is rotating on a cone with a half-angle of 18-degrees at ambient temperature.
Scientific journal, English - STUDY ON CONFORMATIONS OF ETA-ALKANES IN UREA INCLUSION-COMPOUNDS USING CH DIPOLAR SWITCHING-ANGLE SAMPLE SPINNING NUCLEAR MAGNETIC-RESONANCE AND MM2 MOLECULAR MECHANICS CALCULATIONS
F IMASHIRO; D KUWAHARA; T NAKAI; T TERAO
JOURNAL OF CHEMICAL PHYSICS, AMER INST PHYSICS, 90, 6, 3356-3362, Mar. 1989, Peer-reviwed
Scientific journal, English
Lectures, oral presentations, etc.
- Theory of homonuclear REDOR and spin diffusion experimensts and their applications
Daisuke Kuwahara
Invited oral presentation, Japanese, 2013年 固体NMR・材料フォーラム, Society of Solid-State NMR for Materials
Oct. 2013 - 固体回転試料中の同種核スピン系のスピン拡散：拡散速度解析とその応用
桑原大介; 持田智行; 仁木國雄
Oral presentation, Japanese, 第48回NMR討論会講演要旨集／日本核磁気共鳴学会,第48回NMR討論会
Nov. 2009 - 固体NMR法によるイオン液体の新しい基幹物質，デカメチルフェロセン・アセナフテンキノン錯体の研究
中村英章; 桑原大介; 持田智行
Oral presentation, Japanese, 日本核磁気共鳴学会,第47回NMR討論会
Nov. 2008 - Is it possible to directly detect the overtone NMR for half-integer quadrupolar nuclei?
Hajime Okamoto; Yuya Yamazaki; Hiroki Nose; Daisuke Kuwahara
Oral presentation, English, Proceedings of The 1st Asia-Pacific NMR Symposium
Nov. 2005 - Total Spinning Sideband Summation (TOSS sigma)法の開発
芦田淳; 桑原大介; 中井利仁
Oral presentation, Japanese, 第40回 NMR討論会
Nov. 2002 - Overtoneパルスを用いたREDOR信号の計算
桑原大介
Others, Japanese, 第41回NMR討論会
2002 - Novel structure discovered on two-dimensional spin-echo NMR spectra for a homonuclear two-spin system in rotating solids
Daisuke Kuwahara; Toshihito Nakai; Jun Ashida; Seiichi Miyajima
Oral presentation, English, 14th Conference of the International Society of Magnetic Resonance
Aug. 2001
Courses
Research Themes
- 金属錯体で創る機能性液体：物性・反応・空間機能の開拓
持田 智行; 桑原 大介
日本学術振興会, 科学研究費助成事業, 神戸大学, 基盤研究(B), 本課題は、電子物性、化学反応性、および空間機能を有する金属錯体系イオン液体の物質開発を目的とする。本年度は、外場応答性を有する各種の金属錯体系イオン液体の開発を行った。第一に、光反応性を有する金属錯体含有イオン液体の物質開発を行った。ここでは光反応によってオリゴマーまたはアモルファス配位高分子に転換するサンドイッチ型Ru錯体およびその架橋分子混合物を対象として、イオン伝導度および粘弾性の外場応答制御を実証した。さらに、カチオンの分子構造と結晶構造および融点との相関を検証した。第二に、金属錯体含有イオン液体の熱物性に対するキラリティーの効果を調べた。キラル置換基を導入したサンドイッチ型カチオンに対して種々のアニオンを組み合わせた塩を合成し、それらのラセミ体およびキラル体の構造と熱物性を評価し、光学純度に対する相図を作成した。カルボランの塩はイオン性プラスチック結晶相を発現したが、他の塩は多くがイオン液体となった。ラセミ体の結晶相は、カルボランの塩では固溶体、他の塩ではラセミ化合物またはラセミ混合物となった。このように、キラリティーの導入によって多様な相が出現した。第三に、ニトロ・ニトリト光異性化を示すカチオン性金属錯体をイオン液体化した。フッ素系アニオンを用いた塩はイオン液体となった。これらは結晶相では光異性化を示したが、液相およびガラス相では光異性化は認められなかった。この系については、各種のアニオンを組み合わせた塩を用いて、結晶相における光異性化機構を検討した。その結果、この異性化反応は反応空間によって支配されていることが明らかとなった。, 20H02756
01 Apr. 2020 - 31 Mar. 2024 - イオン液体で配位高分子を創る：融けて塗れ、自己修復する配位高分子の開発
持田 智行; 桑原 大介; 藤森 裕基
日本学術振興会, 科学研究費助成事業, 神戸大学, 挑戦的研究(萌芽), 本課題では、イオン液体を素材とする、柔軟性を持つ低融点配位高分子の開発を目的とする。昨年度までに、イオン液体とシアノ系アニオンを含む塩の反応によって、一連のアニオン性配位高分子を合成し、これらの塩が比較的低温で分解融解挙動を示すことを明らかにした。本年度は、詳細な分光学的および熱力学的検討を行うことによって、この特徴的な融解現象の機構解明を進めた。ここでは、得られた物質のうち最も低融点であったイミダゾリウム系イオン液体含有物質を選び、高速熱測定、ラマン分光、およびX線回折を適用して、その融解凝固過程を詳細に検証した。第一に、分解融解後に生じる液相と固相の組成を分析し、この分解融解現象が、融点におけるイオン液体成分と塩の相分離に由来することを明らかにした。すなわち、この系で分解融解が生じるのは、イオン液体に対する溶解度が低い塩を含むことが原因であることがわかった。第二に、高速熱測定を用いて、冷却速度と結晶化度の相関を検証した。これらの物質を融解状態から冷却すると、通常の条件下では必ず不均一な固液混合物を生じたが、極めて早い冷却速度のもとではガラス化が起こることを見出した。このように、本系でアモルファス形成ができることを実証した。第三に、溶融物を冷却して生じた不均一混合物は、放置すると徐々に結晶性の向上を示したが、この過程では、イオン液体と固体成分の反応が常温で進み、元の配位高分子の多結晶が再構成されることがわかった。この結晶再構成は自己修復的な現象ともみなせ、イオン液体成分を含むことに由来する特徴的な現象である。, 20K21210
30 Jul. 2020 - 31 Mar. 2023 - Functional Ionic Liquids Containing Metal Complexes: Electronic Properties, Stimuli Responsiveness, and Gas Absorption Properties
Mochida Tomoyuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Scientific Research (B), A variety of functional ionic liquids containing cationic organometallic complexes and chelate complexes were synthesized. These liquids exhibited unique physical and chemical properties such as thermochromism, chemochromism, photoluminescence, and LCST properties. Ionic plastic crystals and coordination polymers related to these liquids were synthesized, and their structures and properties were elucidated., 16H04132
01 Apr. 2016 - 31 Mar. 2020 - Photogeneration of amorphous metal-organic frameworks from metal-containing ionic liquids
Mochida Tomoyuki
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Challenging Exploratory Research, Ionic liquids were developed that generate amorphous coordination polymers upon UV irradiation. The ionic liquids are composed of cationic ruthenium sandwich complexes and polycyano anions. Upon photoirradiation, the arene ligand in the cation is eliminated and coordination polymer is formed by coordination of the anion to the ruthenium ion. The photogenerated solids exhibited gas adsorption properties due to their microporous structures., 16K13965
01 Apr. 2016 - 31 Mar. 2018 - 吸着剤に付着した未知有機物質の構造解析
桑原大介
石油資源開発株式会社, 研究助成, Principal investigator
11 Jul. 2016 - 31 Mar. 2017 - Preparation of Coordination Polymers from Liquids: Phase Transformation by Heat and Light
Mochida Tomoyuki; KUWAHARA Daisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Challenging Exploratory Research, An ionic liquid has been developed that transforms into an amorphous coordination polymer when exposed to ultraviolet light and returns to liquid form when heated. The solid-liquid transformation is fully reversible. The ionic liquid contains a cationic ruthenium sandwich complex with cyano groups. This study reveals a method that creates coordination polymers by exposing liquids to light., 26620046
01 Apr. 2014 - 31 Mar. 2016 - Preparation and Properties of Ionic Liquids from Metal Complexes
Mochida Tomoyuki; TAKAHASHI Kazuyuki; KUWAHARA Daisuke; TAKAHASHI Masashi; FUJIMORI Hiroki; KATO Keisuke; HAYASHI Masahiko
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Scientific Research (B), Functional metal-containing ionic liquids were synthesized from various cationic metal complexes. First, ionic liquids exhibiting vapochromic, magnetic, and other properties were developed from chelate complexes. Second, a series of ionic liquids were synthesized from metallocenium complexes, and their physical properties and chemical reactivities investigated. Correlations between the crystal structures and thermal properties of metallocenium salts were also investigated., 24350073
01 Apr. 2012 - 31 Mar. 2016 - Development of liquid catalysts exhibiting ionic conductivity
MOCHIDA Tomoyuki; KUWAHARA Daisuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Challenging Exploratory Research, This study aims at developing liquid catalysts having ionic conductivity. By applying the molecular design that we developed earlier, a variety of ionic liquids were prepared from metal complexes having catalytic activities. First, Ru-containing ionic liquids were prepared from arene-Ru complexes bearing various bidentate ligands. These salts exhibited high catalytic activities toward the oxidation of alcohols, but the complexes were found to undergo gradual decomposition during the reaction. Second, Cu-containing ionic liquids were prepared from Cu complexes bearing tripod ligands. Ligands containing alkyl-imidazole moieties were designed. Cu(I) complexes were highly unstable; however, Cu(II) complexes were isolated as solids or highly viscous liquids., 24655126
01 Apr. 2012 - 31 Mar. 2014 - Metallocenium Ionic Liquids: Preparation, Electronic Properties, and Chemical Reactivities
MOCHIDA Tomoyuki; NISHIO Yutaka; KUWAHARA Daisuke; HAYASHI Masahiko; SAITO Toshiaki; KANADANI Chikahide; TAKAHASHI Masashi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Kobe University, Grant-in-Aid for Scientific Research (B), A series of metal-containing ionic liquids that are based on metallocenium cations were developed. The thermal properties, magnetic properties, and chemical reactivities of these ionic liquids were investigated., 21350077
2009 - 2011 - フェロセン系分子からなる新しいイオン液体の設計と微視的評価
持田 智行; 高橋 正; 桑原 大介
日本学術振興会, 科学研究費助成事業, 神戸大学, 萌芽研究, 今年度は、前年度合成法を開発したフェロセニウム系イオン液体について、多様な誘導体を合成し、それらの粘度、熱物性、磁気特性の評価を進めた。 1置換もしくは2置換フェロセニウムカチオンとフッ素系アニオンを組み合わせた塩は、そのほとんどが融点100℃以下のイオン液体となった。これらの液体はヘキサンなどの非極性溶媒とは相溶しないが、極性有機溶媒とは良好な相溶性を示した。水に対する溶解性は置換基によって変化した。 熱分析によって、系の特徴を明らかにした。第1に、融点のカチオン依存性を検討した。カチオンのアルキル基を伸長すると、融点の急激な低下がみられた。分枝アルキル体では、直鎖体より数十度融点が増加した。第2に、TFSI系アニオンの炭素鎖伸長の効果を検討した。この場合、融点はほとんど変化せず、粘度のみが急激に増加した。すなわちカチオンの置換基は融点、アニオンの置換基は粘度に主たる影響を与えることが明らかとなった。第3に、粘度と相挙動の相関について検討を加えた。これらの液体には、(i)冷却過程で結晶化するもの、(ii)ガラス化するもの、(iii)条件によって結晶化・ガラス化を起こすもの、の三種が存在し、低粘度の塩は結晶化、高粘度の塩はガラス化を起こすことがわかった。 メスバウアー分光によって、フェロセニウム塩の結晶およびガラス状態における格子力学的検討を行い、分子運動性の差を定量的に評価した。また固体NMR分光により、相変化に伴うスペクトル変化を検証した。 これらの磁気物性についても検討を加えた。磁化率測定の結果、フェロセニウム系イオン液体は常磁性流体であることがわかった。特に強磁場中では、結晶化・融解に伴って、ヒステリシスを伴う顕著な磁化率の変化が認められた。, 19655053
2007 - 2008 - 超音波振動照射による巨大蛋白質のプロトン高分解能NMR測定法の開発
桑原 大介
日本学術振興会, 科学研究費助成事業, 電気通信大学, 萌芽研究, 本研究では,超音波振動子を用いて,溶媒とそこに加えられた"分子量の大きな蛋白質試料"を激しく揺動させることを目指している.この状態の下でNMR信号を観測することにより,巨大蛋白質のプロトンNMRスペクトルの分解能を,格段に向上させることを目的とする.今年度は 最初にNMR信号に混入してくる高周波ノイズをデカップルするための方式(バイパスコンデンサ方式)を見直すことを行った.最初の工夫としてNMRプローブ内部に銅管を逼し,その中に超音波振動子駆動電流ラインを通すことを行った.さらに銅管の接地面と電流ラインの間にバイパスコンデンサを数個挿入する工夫を行ったところ,NMR信号に混入するノイズ強度は,以前と比較して半分以下となった.この他にもNMRプローブ自体のグランドラインの接地を工夫してみたが,目だった効果は現れなかった.高周波ノイズの問題はある程度改善できたので,続いて超音波振動子の最適化を行うことにした.TiZrセラミック振動子については,ソフト材とハード材2種類のものを用いた.それぞれをNMRプローブに設置した後,振動周波数を100kHz〜800kHzまで変えて1^H NMR測定を行った.試料としては,アダマンタンを溶媒に加えた標準試料を用いた.その結果,ハード材TiZrセラミック振動子を用いて300kHzの振動を加えた場合に,最も高い分解能が得られることが判明した.この後は標準試料を離れて,巨大蛋白質のモデル物質であるTentaGelビーズ直結高分子を使って実験を行う予定である., 18655029
2006 - 2007 - メタンハイドレートの構造解析に関する研究
（独）石油天然ガス・金属鉱物資源開発機構
01 Apr. 2005 - 31 Mar. 2006 - 試料回転を行っている固体中の同種核2スピン系が運動している場合のNMRスペクトル
桑原 大介
日本学術振興会, 科学研究費助成事業, 岡崎国立共同研究機構, 奨励研究(A), 試料回転下にある固体中の同種核2スピン系がn個のサイト間をジャンプしている場合に、NMRスペクトルがどのように変化するかを計算するために、数値積分法を用いてマスター方程式を積分する理論を完成させた。その理論に基づいてNMRスペクトルを計算するプログラムを作成し大型計算機上で実行させたが、スピン系が2サイト間ジャンプあるいは3サイト間ジャンプをしている場合までは実用的な計算時間に収めることができた。最初に、off magic angleで回転している^<13>C-^<13>C2スピン系が、その結合方向に垂直な軸の周りにジャンプ運動を行っている場合のNMRスペクトルを計算した。運動モデルはそのまま試料回転軸をmagic angleとし、rotational resonance条件のもとで現れる粉末パターンが運動速度とともにどのように変化するかも計算した。さらに^<13>C-^<13>C2スピン系の一方のスピンが正四面体の中心に位置し、もう一方が3つの頂点を飛び移っている場合の計算も行った。計算の結果、同種核2スピン系のNMRスペクトルは、系がどのような運動を行っているかをよく反映することがわかった。そしてこの系のNMRスペクトルを解析すれば固体状態の物質中に存在する分子運動のみならず、分子の配座変換を直接検出できることを示した。しかし、スピン系が4サイト以上のポテンシャル最小位置間をジャンプしている場合を計算しようとすると、本研究で用いた数値積分法では膨大な計算時間を必要とすることも判明した。, 07740479
1995 - 1995