Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.poly.2021.115444

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DOI： 10.1246/BCSJ.20190085

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DOI： 10.1246/BCSJ.20180320

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DOI： 10.1515/ZNB-2018-0109

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Authorship：Lead author,　Corresponding author   Language：Japanese  

CiNii Books

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Spherical-type cations of 1-alkyl-4-aza-1-azoniabicyclo-[2,2,2]octane (N-R DABCO, R = Me, Et) form ionic plastic crystals with BEt3Me- and BEt4-. Differential scanning calorimetry (DSC) analysis of [N-R DABCO][BEt3Me] and [N-R DABCO][BEt4] shows entropy changes of 49-73 JK(-1) mol(-1) at transition temperatures for the highest-temperature solid phase. X-ray diffiaction (XRD) spectra show these salts form CsCl-type cubic structures. H-1 and C-13 nuclear magnetic resonance (NMR) shows that the cation and anion undergo isotropic reorientation in the highest-temperature solid phase. NMR spin-lattice relaxation times (T-1) reveal that activation energies for this motion are smaller than reported for [NEtxMe(4-x)][BEt3Me] (x = 0-4), in contrast, electrical conductivity measurements show activation energies of ion transfer for these salts are similar to those of [NEtxMe(4-x)][BEt3Me]. In contrast to [N-R DABCO][BEt3Me-, BEt4-] salts, [N-R DABCO][BBu4] (R = Me, Et, Pr, Bu) show large entropy changes at their melting points. Complex XRD powder patterns and broad NMR spectra were also obtained. Based on these results, it can be concluded that the [N-R DABCO][BBu4] compounds show no plasticity under ambient conditions.

DOI： 10.1246/bcsj.20150246

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WALTER DE GRUYTER GMBH  

Eight plastic crystals of the types NEtxMe(4-x)BEt4 and NEtyPr(4-y)BEt4 (x = 0-4, y = 1-3) were found in a new region of ionic plastic crystals. In this area, globular cations and anions are assembled by weak interactions. Based on the results of solid-state H-1 and C-13 nuclear magnetic resonance (NMR) measurements, it was revealed that the ions performed isotropic reorientations in the NEtxMe(4 -x)BEt4 crystals (x = 0-4). Additionally, X-ray diffraction (XRD) of these compounds was able to identify the CsCl-type cubic structure. In contrast, the XRD reflections of NEtyPr(4-y)BEt4 (y = 1-3) could be successfully fitted by distorted cubic lattices (trigonal symmetry). The NMR line shapes observed in these compounds were explained by overall molecular motions with large amplitudes (pseudo-isotropic reorientations). Differential scanning calorimetry (DSC) spectra of NEtyPr(4-y)BEt4 (y = 1-3) showed a low entropy change (Delta S-mp) of 6-8 J K-1 mol(-1) at the melting point. Ionic diffusion was identified by electrical conductivity measurements of NEtxMe(4 -x)BEt4 and NEtyPr(4-y)BEt4 (x = 0-4, y = 1-3). In the case of NPr4BEt4 crystals, ionic diffusion was also detected, although complex powder patterns and large Delta S-mp values were observed by XRD and DSC measurements, respectively.

DOI： 10.1515/zna-2015-0105

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Electrical conductivity (sigma), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) measurements of n-C (x) H ((2x+1)) OSO Li-3 (x= 12, 14, 16, 18, and 20) crystals were performed as a function of temperature. In addition, sigma, DSC, and XRD observations of n-C (x) H ((2x+1)) OSO Na-3 and n-C (x) H ((2x+1)) OSO K-3 (x= 12, 14, 16, 18, and 20) crystals were carried out for comparison. DSC results of the salts revealed several solid-solid phase transitions with large entropy changes (Delta S). For n-C (18) H (37) OSO Li-3 and n-C (20) H (41) OSO Li-3 salts, each melting point produced a small Delta S (mp) value compared with the total entropy change in the solid phases (Delta S (tr1)+Delta S (tr2)). Additionally, Li (+) ion diffusion was detected in the highest temperature solid phases. For K salts, larger sigma values were detected for potassium alkylsulfates compared with those reported for alkyl carboxylate. Li-7 NMR spectra of n-C (18) H (37) OSO Li-3 crystals recorded in the low-temperature phase showed large asymmetry parameters, suggesting the Li (+) ions are localized at asymmetric sites in the crystals.

DOI： 10.1007/s10751-014-1087-7

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We have developed a new cooling material that uses vaporization heat. This system consists of poly(N-isopropylacrylamide) [P(NIPAAm)] and C2H4-permeated mesoporous silica [MCM(C2H4)]. Although the polymer can dissolve in water below ca. 32 degrees C (above this temperature, it is insoluble in water), H-1 nuclear magnetic resonance spectroscopy showed that P(NIPAAm) adsorbed on MCM(C2H4) became water resistant below 32 degrees C. In addition, this system retained hydrophobic-hydrophilic switching at ca. 32 degrees C. When this material was used in a house model, the system absorbed water molecules from air during the night (below ca. 32 degrees C), and the room temperature was decreased by ca. 4 degrees C when the outside temperature exceeded ca. 32 degrees C. This system can cool rooms on hot days without using any electrical or human energy.

DOI： 10.1246/bcsj.20140187

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New plastic crystals of NEt3PrBBu4 and NEt2Pr2BBu4 were formed in a new region of ionic plastic crystal. In this area, globular cations and anions are assembled by weak interactions. Differential scanning calorimeter (DSC) measurements of these salts showed a low entropy change of 19.6 and 14.0 J K-1 mol(-1) at each melting point, respectively. On the basis of solid-state H-1 and C-13 nuclear magnetic resonance (NMR) spectra and electrical conductivity measurements, isotropic reorientation and ion transfer of globular cations and anions were detected in these crystals. The other compounds of NEtxMe(4-x)BBu4 (x = 1-3) showed tumbling motions and low activation energies of self-diffusion in crystals.

DOI： 10.5560/ZNA.2014-0029

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New ionic plastic crystals of NR4BEt3Me (R = Me and Et) and NRxR'(4-xBEtMe)-Me-3 (R = Et, R' = Me and Pr, x = 1-3) were formed in a new region of plastic crystal. In this area, globular cations and anions are assembled by weak interactions. On the basis of our results of H-1 and C-13 NMR spectra and electrical conductivity measurements, we could conclude that isotropic reorientation and self-diffusion of globular cations and anions were detected in the crystal. X-ray diffraction (XRD) lines observed in RxR'4-xBEt3Me (R = Et, R' = Me, x = 0-4) revealed a CsCl-type cubic crystal structure. Additionally, DSC spectra revealed that this new class of plastic crystals displays low phase-transition temperatures in the plastic phase and have high melting points. The former tendency is frequently detected in molecular plastic crystals while the latter is often found in ionic plastic crystals.

DOI： 10.1246/bcsj.20130040

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Differential scanning calorimetry (DSC) thermograms, X-ray diffraction (XRD) analysis, electrical conductivity (sigma), and Li-7 NMR spectroscopy characterization of n-C (m) H(2m + 1)COOM solids (M = Li, Na, K; m = 13, 15, 17, 19, 21) and mixed crystals n-C21H43COOLi (x) K(1 -x) (0.25 pound x <= 0.75) was performed as a function of temperature. DSC thermograms of n-C (m) H(2m +1)COOM revealed several solid-solid phase transitions with large entropy changes. Electrical conductivity studies established that n-C (m) H(2m + 1)COOLi crystals are poor electrical conductors. In contrast, n-C (m) H(2m + 1)COOK salts were found to have sigma values of 10 (-7)-10 (-8) S.cm (-1). Since the crystal structures and phase-transition temperatures of both n-C (m) H(2m + 1)COOLi and n-C (m) H(2m + 1)COOK crystals were similar, they were able to form mixed crystals with the structure n-C (x) H(2m + 1)COOLi (x) K(1 -x). DSC thermograms of the mixed crystals showed a small entropy change at the melting point (Delta S (mp) < 13 J K (-1) mol (-1)), in addition, large Delta S values at the solid-solid phase transition temperature. The sigma values obtained for mixed crystals were roughly one order of magnitude greater than those determined for n-C21H43COOK crystals. Li-7 NMR spectra of the mixed crystals recorded at various temperatures suggested that the self-diffusion of Li (+) ions was excited in the highest-temperature solid phase. Based on these results, we have classified these mixed crystals as rotator crystals.

DOI： 10.1007/s10751-012-0670-z

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Chemical shifts (CS) of the H-1 nucleus in N center dot center dot center dot H center dot center dot center dot O type hydrogen bonds (H- bond) were observed in some complexes between chlorophenols [ pentachlorophenol (PCP), 2,4,6- tricholorophenol (TCP), 2,6- dichlorophenol (26DCP), 3,5- dichlorophenol (35DCP), and p- chlorophenol (pCP)] and nitrogen- base (N- Base) by solid- state high- resolution H-1- NMR with the magic- angle- spinning (MAS) method. Employing N- Bases with a wide range of pK(a) values (0.65- 10.75), H-1- MAS- NMR CS values of bridging H atoms in H- bonds were obtained as a function of the N- Base's pK(a). The result showed that the CS values were increased with increasing pKa values in a range of Delta pKa < 0 [Delta pK(a) = pK(a)(N- Base) - pK(a)(chlorophenols)] and decreased when Delta pK(a) > 2: The maximum CS values was recorded in the PCP (pK(a) = 5.26)- 4- methylpyridine (6.03), TCP (6.59)- imidazole (6.99), 26DCP (7.02)- 2- amino- 4- methylpyridine (7.38), 35DCP (8.04)- 4- dimethylaminopyridine (9.61), and pCP (9.47)- 4- dimethylaminopyridine (9.61) complexes. The largest CS value of 18.6 ppm was recorded in TCP- imidazole crystals. In addition, H/D isotope effects on H-1- MAS- NMR spectra were observed in PCP- 2- amino- 3methylpyridine. Based on the results of CS simulation using a B3LYP/6- 311+ G** function, it can be explained that a little changes of the N- H length in H- bond contribute to the H/D isotope shift of the H-1- MAS- NMR peaks.

DOI： 10.3390/molecules18044786

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Anomalous H/D isotope effects were detected in the 1H MAS NMR spectra of piperidinium p-chlorobenzoate (C5H10NH2+·ClC6H4COO-) upon deuterium substitution of hydrogen atoms which form two kinds of N-H⋯O H-bonds in the crystal
in contrast to these spectra, only slight chemical shifts were recorded in 13C CP/MAS NMR spectra. 2H NMR spectrum of the deuterated sample show quadrupole coupling constants of 148 and 108 kHz, and reveal that there are a few motions contributing to the electric-field modulation of the 2H nucleus. The 1H MAS NMR spectra of piperidinium p-chlrobenzoate-d16 (C5D10ND2+·ClC6D4COO-) and -d14 (C5D10NH2+·ClC6D4COO-) revealed that the change in the envelope is caused by chemical shifts of each signal upon deuteration. Calculations based on the density-functional-theory showed that the N-H distance along the crystallographic a-axis mainly contributes to the anomalous isotope effects on 1H MAS NMR envelopes. © 2012 Springer Science+Business Media Dordrecht.

DOI： 10.1007/s10751-012-0671-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A new synthesis route has been established to prepare highly pure mesoporous silica material (Si-MCM-41) with rod-like morphology. To improve the stability and to bring about the long range ordering in the mesoporous material, a series of tetra-alkylammonium salts has been employed in the new procedure in addition to the surfactant, cetyl-trimethylammonium bromide. The mesoporous silica materials have been characterized by small-angle X-ray diffraction (SAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 sorption and solid state Si-29 NMR measurements. The XRD study revealed that an excellent long range structural ordering of mesoporous material can be achieved using tetrabutylammonium bromide as a promoter. SEM study showed that rod-shaped single crystal like particles were formed in hydrothermal synthesis. TEM study revealed the presence of hexagonal voids on the face of the rod-shaped particles while nitrogen sorption study establishes the mesoporosity of the material. A high degree of cross-linking of-Si-O-Si- networks in the mesoporous silica has been evidenced in Si-29 NMR study. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.clay.2011.07.018

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An anomalous isotope effect was observed in the (35)C1NQR frequency of pyrrolidinium p-chlorobenzoate (C4H8NH2+center dot C1C(6)H(4)COO(-)) by deuterium substitution of hydrogen atoms which form two kinds of N-H center dot center dot center dot O type hydrogen bonds. Large negative frequency shifts of the 35CI resonance lines, reaching 309 kHz at 77K and 267 kHz at 293K, were obtained upon deuteration, although the Cl atom in the molecule formed no hydrogen bonds in the crystal. H-1 MAS NMR lines showed significant changes by the deuterium substitution, while in contrast, small shifts of (CCP)-C-13/ MASNMR signals were obtained. Our measurements of H-1 NMR spin-lattice relaxation times (T-1) suggested that the H/D isotope shifts detected from the (35)C1NQR frequencies and 1H NMR spectra are due to structural changes rather than molecular dynamics. Single-crystal X-ray diffraction measurements showed two remarkable H/D isotope differences in the molecular arrangements, (i) the N-H length along the crystallographic a axis became I pm shorter, and (ii) the dihedral angle between benzene and the pyrrolidine ring changed by 1.1(2)degrees upon deuteration. Using density functional theory estimations, the anomalous (35)C1NQR frequency shifts and H-1 MASNMR line-shape changes could be explained by the dihedral angle change rather than the N-H length difference.

DOI： 10.1246/bcsj.20090300

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The [Sn(salen)](2+) complex moiety has been immobilized into NaY zeolite by in situ synthesis of the salen complex in NaY matrix to prepare a new catalyst, Sn(salen)-NaY. The catalyst has been characterized by UV-vis, infrared (IR) spectroscopy, X-ray powder diffraction. Mossbauer and Sn-119 NMR spectroscopy. The catalyst shows impressive catalytic performance (with high selectivity) in Baeyer-Villiger oxidation of various cyclic ketones including 2-adamantanone, cyclohexanone, cyclopentanone, 4-methylcyclohexanone, 2-methylcyclohexanone using tert-butyl hydroperoxide (tert-BuOOH) as an oxidant. The yield of epsilon-caprolactone from catalytic oxidation of cyclohexanone over Sn(salen)-NaY catalyst was ca. 75%. The catalyst can be recycled for several times without any major decline in catalytic activity. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2010.04.029

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H/D isotope effects onto Br-79 NQR frequencies of piperidinium p-bromobenzoate were studied by deuterium substitution of hydrogen atoms which form two kinds of N-H center dot center dot center dot O type hydrogen bonds, and the isotope shift of ca. 100 kHz were detected for a whole observed temperature range. In addition, H-1 MAS NMR spectra measurements of piperidinium and pyrrolidinium p-bromobenzoate were carried out and little isotope changes of NMR line shape were detected. In order to reveal effects of molecular arrangements into the obtained isotope shift of NQR frequencies, single-crystal X-ray measurement of piperidinium p-bromobenzoate-d2 and density-functional-theory calculation were carried out. Our estimation showed the dihedral-angle change between piperidine and benzene ring contributes to isotope shift rather than those of N-H lengths by deuterium substitution.

DOI： 10.1007/s10751-010-0198-z

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Anomalous isotope effects were detected in the (35)Cl nuclear quadrupole resonance (NQR) frequency of piperidinium p-chlrobenzoate (C(5)H(10)NH center dot ClC(6)H(4)COOH) by deuteration of hydrogen atoms. The atoms were determined to form two kinds of N-H center dot center dot center dot O type H-bonds in the crystal structure. Large frequency shifts of the (35)Cl resonance lines reaching 288 kHz at 77 K and 278 kHz at room temperature were caused upon deuteration, in spite of the fact that the Cl atoms in the molecule do not form hydrogen bonds in the crystal. Results of single crystal X-ray diffraction measurements and density-functional-theorem calculations suggest that a dihedral-angle change of 1.8 degrees between benzene and the piperidine ring contributes to (35)Cl NQR anomalous frequency shifts.

DOI： 10.1007/s10751-008-9701-1

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Using H-1 NMR T-1 and T-1 rho measurements self-diffusion of NH4+ with an activation energy of (80 +/- 10) kJ mol(-1) was detected in the highest-temperature phase of NH4NO2 crystals. Narrow N-15 NMR spectra of (NH4NO2)-N-15 and (NH4NO2)-N-15 revealed that the isotropic reorientation rates of NH4+ and NO2-ions are rapid in the high-temperature solid phase. These results suggest that the high-temperature phase of NH4NO2 crystals forms an ionic plastic phase.

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We report a solid-state O-17 NMR study of the O-17 electric-field-gradient (EFG) and chemical shielding (CS) tensors for each carboxylate group in polycrystalline L-alanine and L-phenylalanine. The magic angle spinning (MAS) and stationary O-17 NMR spectra of these compounds were obtained at 9.4, 14.1, and 16.4 T. Analyzes of these O-17 NMR spectra yielded reliable experimental NMR parameters including O-17 CS tensor components, O-17 quadrupole coupling parameters, and the relative orientations between the O-17 CS and EFG tensors. The extensive quantum chemical calculations at both the restricted Hartree-Fock and density-functional theories were carried out with various basis sets to evaluate the quality of quantum chemical calculations for the O-17 NMR tensors in L-alanine. For O-17 CS tensors, the calculations at the B3LYP/D95** level could reasonably reproduce O-17 CS tensors, but they still showed some discrepancies in the 61 1 components by approximately 36 ppm. For O-17 EFG calculations, it was advantageous to use calibrated Q value to give acceptable C-Q values. The calculated results also demonstrated that not only complete intermolecular hydrogen-bonding networks to target oxygen in L-alanine, but also intermolecular interactions around the NH3+ group were significant to reproduce the O-17 NMR tensors. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molstruc.2006.12.034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

We report the first experimental determination of the carboxylate oxygen electric-field-gradient (EFG) and chemical shielding (CS) tensors in polycrystalline gamma-glycine. Analysis of magic-angle spinning (MAS) and stationary O-17 NMR spectra of [O-17]-gamma-glycine obtained at 9.4, 14.1, 16.4, and 18.8 T yields the magnitudes of the O-17 EFG and CS tensors and the relative orientations between the two tensors. Extensive quantum chemical calculations at both the restricted Hartree-Fock and density functional levels have been performed to present the absolute tensor orientations in term of the molecular frame. We have demonstrated that 170 NMR tensor information could be unambiguously derived by the multiple field analyses of stationary O-17 NMR spectra. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.ssnmr.2006.09.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

We have presented an experimental investigation of the carboxyl oxygen NMR parameters for four distinct sites in L-valine and L-isoleucine. The carboxyl O-17 quadrupolar coupling constant, C-Q, and isotropic chemical shift, delta(iso), for these compounds are obtained by analyzing two-dimensional O-17 multiple-quantum magic-angle spinning (MQMAS) and/or 1D MAS spectra. The values of C-Q and delta(iso), found to be in the range of 7.00-7.85 MHz, and 264-314 ppm, respectively. Extensive quantum chemical calculations at the density functional levels have been performed for a full cluster Of L-valine molecules and a few theoretical models. The calculated results indicated that there was a correlation between the O-17 NMR parameters and C-O bond lengths, which was helpful for the spectral assignment. They also demonstrated that the torsion angle Of L-valine plays an important role in determining the magnitudes of O-17 NMR parameters. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.ssnmr.2006.09.003

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Cl-35 NMR spectra were measured using the highest-temperature solid phase of n-CxH(2x+l) NH3Cl and n-CxH((2x+1))ND3Cl (x = 5 - 10). The observed quadrupole coupling constants (e(2)Qqh(-1)) decreased upon heating in this phase, and significant frequency differences of ca. 20 - 30 kHz were detected between the -NH3 and -ND3 analogs. In the low-temperature range of this phase, the observed e(2)Qqh(-1) values for x = 8, 10 were larger than those for x = 5, 7, 9, which is attributable to the even-odd effect. Point-charge calculation was employed to explain this effect, in which the geometrical parameters and electric charge distributions of the cations were estimated using the B3LYP/6-31G* and B3LYP/6-31+G** method, respectively. The results show that the double-layer width between the Cl- ions at the 2a and 4f sites strongly contributes to the e(2)Qqh(-1) value.

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The temperature dependences of Li-7 and N-15 NMR spin-lattice relaxation times and spectra in LiNO2 were measured in the range 120 K - 473 K (m.p.). The 180 degrees-flip motion of NO2- ions along or perpendicular to the molecular C-2-axis and the self-diffusion of Li+ ions (activation energies of 42 - 44 and 100 kJ mol(-1), respectively) were observed in this range. From the comparison of the observed activation parameters with those reported for plastic phases of alkali metal nitrites, a new characteristic of the plastic crystal was obtained.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We made neutron powder diffraction measurements for phase Ill (at 4, 120, 180, 220, and 250 K) and phase II (at 280 K) of KNO2. The structure of phase III was determined by the Rietveld method using the data, obtained at 4 K; the initial structure parameters were obtained by a systematic trial-and-error method. Phase III is monoclinic (space group: P2(1)/c) with a = 4.4010(2) Angstrom, b = 9.5967(3) Angstrom, c = 6.9817(2) Angstrom, beta = 108.274(3)degrees, and Z = 4. Both K+ and NO2- ions are located at general positions, and the orientations of the NO2- ions are completely ordered. The structures of phase III at the higher temperatures were also examined on the basis of the structure at 4 K. The atomic displacement parameters of the NO2- ions increased anomalously with increasing temperature, indicating gradual but remarkable development of the orientational disorder of NO2- ions. The structure of phase II was determined to be rhombohedral (space group: R(3) over barm$) with a = 5.02790(4) Angstrom, c = 10.05587(3) Angstrom, and Z = 3. The orientations of the NO2- ions were highly disordered about the (3) over bar axis.

DOI： 10.1088/0953-8984/10/15/011

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The complex dielectric permittivity of ionic plastic crystal KNO2 was measured in the frequency range 20-10(6) Hz and the temperature range 22-300 K. A small step-like anomaly of the static dielectric permittivity appeared at the rhombohedral (phase II) to monoclinic (phase III) transition (T-tr2 = 264.1 K). In phase III, the static dielectric permittivity decreased gradually on cooling over a wide temperature range 50-264 K. These results indicate that the orientation of the NO2- ion is still disordered at high temperatures in phase III and becomes ordered gradually with decreasing temperature. The dielectric dispersion associated with this motion occurred in-the temperature range 70-150 K. From these data and the previously reported N-15 NMR data, we propose a model of the motion of NO2- in phase III in which the anion undergoes 180 degrees-flip motion about the axes perpendicular to the molecular C-2 axis in an asymmetric double-minimum potential.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-VCH Verlag  

The complex dielectric permittivity of ionic plastic crystal KNO2 was measured in the frequency range 20-106 Hz and the temperature range 22-300 K. A small step-like anomaly of the static dielectric permittivity appeared at the rhombohedral (phase II) to monoclinic (phase III) transition (Ttr2 =264.1 K). In phase III, the static dielectric permittivity decreased gradually on cooling over a wide temperature range 50-264 K. These results indicate that the orientation of the NO2- ion is still disordered at high temperatures in phase HI and becomes ordered gradually with decreasing temperature. The dielectric dispersion associated with this motion occurred in the temperature range 70-150 K. From these data and the previously reported 15N NMR data, we propose a model of the motion of NO2- in phase III in which the anion undergoes 180°-flip motion about the axes perpendicular to the molecular C2 axis in an asymmetric double-minimum potential. © WILEY-VCH Verlag GmbH, 1998.

DOI： 10.1002/bbpc.19981020204

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The temperature dependence of thel5N and l33Cs NMR spin-lattice relaxation times, the l5N spin-spin relaxation time, and the l5N and 133Cs spectra of CsNOz was observed in the plastic phase (209.2&lt
T&lt
673K(m.p.)) and the low-temperature phase (Phase II). In Phase II we found the N07 180°-flip, which could be attributed to the anomalous increase of the heat capacity curve, and determined the activation energy of this motion to be 8.7-11.7 kJ mol~1. The l
N and L33Cs spectra in this phase are inconsistent with the reported crystal structure R3m and can be explained by lower crystal symmetry. In the plastic phase we detected a new anionic motion with 11 kJ mol-1, an isotropic N07 reorientation with 8.5-9 kJ mol-1, and ionic self-diffusion with 47 kJ mol-1. The presence of ionic self-diffusion was confirmed by measuring the electrical conductivity. © 2014, Verlag der Zeitschrift für Naturforschung. All rights reserved.

DOI： 10.1515/zna-1996-5-668

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The temperature dependences of the NMR spin-lattice and spin-spin relaxation times and the NMR spectra of N-15 in (TlNO2)-N-15 were observed in the plastic phase (282.4 K < T < 459 K) and the low-temperature phase. From the analysis of N-15 NMR data, we attributed the motion reported in dielectric and Tl NMR studies in the low-temperature phase to the 180 degrees-flip of NO2- ions which takes place with an activation energy of 14 kJ mol(-1). In the plastic phase, we detected isotropic NO2- reorientation with an activation energy of 13.5 kJ mol(-1) and a new anionic motion with 10 kJ mol(-1).

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：VCH PUBLISHERS INC  

Temperature dependences of NMR spin-lattice relaxation times T-1 of N-15, N-14, Rb-85 and Rb-87, spin-spin relaxation times T-2 of N-14 and Rb-87, and NMR spectra of N-15 and Rb-87 in RbNO2 were observed in the plastic phase (Phase I) and the low-temperature phase (Phase II) obtainable below 264 K. We showed the presence of a new NO2- motion in Phase II with an activation energy of 12- 15 kJ mol(-1). This motion was assigned to NO2- reorientation about its C-2-axis by referring to the temperature dependence of the N-15 chemical-shift anisotropy and the reported data of the dielectric dispersion. In the plastic phase, we detected the NO2- isotropic reorientation with an activation energy of 6.2 kJ mol(-1) and the ionic self-diffusion with 110 kJ mol(-1), which was confirmed by measuring electrical conductivity.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：VERLAG Z NATURFORSCH  

The temperature dependence of the Br-81 NQR frequencies (nu(D)) for uncoordinated Br- ions in trans-[CoBr2(en)2] [D5O2)Br2 (D) has been determined by a continuous-wave spectrometer. nu(D) amounted to 16.200 MHz at 273 K. This is lower by 418 kHz than the Br-81 NQR frequency (nu(H)) for trans-[CoBr2(en2] [H5O2]Br2 (H). The frequency difference (DELTA(nu) = nu(H) - nu(D)) remained almost constant in the temperature range studied. A shortening of the O - H bond length caused by deuteration could explain the magnitude and the sign of DELTAnu on the basis of a point charge model calculation. The compounds D and H yielded Br-81 NQR lines in the range 110-320 K and 90-343 K, respectively. As to the Co-59 NQR frequencies nu1 (7/2-5/2), the observed isotope frequency shifts (DELTAnu1 = nu1H-nu1) between D and H were smaller than 5 kHz. Below 160 K, Co-59 resonances were only available by pulsed experiments. Co-59 NQR spin-lattice relaxation times T1Q of 0.54 ms at 194 K and 4.8 s at 77 K for H have been observed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VERLAG Z NATURFORSCH  

The spin-lattice relaxation time of K-39 NMR observed in the low-temperature phase (T < 264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2- rotation as well as the self-diffusion were shown in the intermediate phase (T less-than-or-equal-to 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing K-39 and N-15 NMR relaxation times and N-15 lineshapes.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VERLAG Z NATURFORSCH  

A single Br-79 NQR line showing a frequency of 19.594 MHz at room temperature has been observed in the crystals of trans-[CoBr2(en)2][H5O2]Br2 and assigned to the Br- ions which are not coordinated to the central Co(III) atom. The electric field gradient (EFG) at the Br- nuclei arises from O-H...Br- hydrogen bond formation between the Br- ions and the terminal O-H hydrogen atoms in [H5O2]+ ions. The induced EFG is greater for the present bromine complex than that for the isostructural chlorine complex. A point charge model calculation explains well the relative magnitude of the EFG in the two crystals by introducing Sternheimer's antishielding factors for the halogen ions.

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Event date： 2023.9

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