2H and 195 Pt NMR Studies of Molecular and Electron Spin Dynamics in Paramagnetic [Cu(H2O)6][PtCl 6]

1998 ◽  
Vol 53 (6-7) ◽  
pp. 447-452
Author(s):  
Takahiro Iijima ◽  
Kengo Orii ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Activation Energy ◽  
Electron Spin ◽  
Nmr Spectra ◽  
Chemical Shift Anisotropy ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Temperature Phase ◽  
Nmr Studies ◽  
Teller Distortion ◽  
Exponential Factor

Abstract The temperature dependences of 2H and 195Pt NMR spectra and the spin-lattice relaxation time T1 were measured for [Cu(H2O)6][PtCl6]. From the simulation of 2H NMR spectra, the jump rate of 180° flips of the water molecules (k), the nuclear quadrupole interaction parameters (e2Qq/h, ƞ) and the electron-nucleon dipolar interaction parameter (vD) were obtained. By measuring 2H T1, k was estimated in the temperature range where the spectrum is insensitive to the motion of the water molecules. Above the phase transition temperature, the pre-exponential factor k0 = 8 x1011 s-1 and the activation energy Ea = 15 kJmol-1 for 180° flips of the water molecules were obtained from the spectral simulation and T1. 195Pt NMR spectra showed an axially symmetric and unsymmetric powder pattern of the chemical shift anisotropy at the high and low temperature phase, respectively. For the deuterated compound, the correlation times of the electron spin in Cu2+ were estimated from 195Pt T1 and the activation energy for jumping between the different configurations of Jahn-Teller distortion Δ = 200 K was obtained.

scholarly journals NMR Studies on Dynamics of Water Intercalated in Clay Minerals

1999 ◽  
Vol 54 (6-7) ◽  
pp. 431-436 ◽  
Author(s):  
Shin’ichi Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Nmr Spectra ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Axial Rotation ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Nmr Studies ◽  
Spin Lattice ◽  
H Nmr ◽  
Clay Layers

Abstract The dynamics of water molecules intercalated in D2O saturated synthetic and natural smectites, and a synthetic Na-fluormica were studied by measurements of solid state 2H NMR spectra and spin-lattice relaxation times at 150 - 370 K. The obtained results could be explained by the 2-site flip, the C2 rotation and the isotropic rotation of the D2O molecules in smectites. In fluormica, the isotropic motion was undetectable, but the axial rotation of the hydration sphere as a whole was observed. The activation energies and correlation times of the C2 rotation were almost independent of the interlayer cations but depended on the character of clay-layers.

NMR Studies on the Dynamics of Intercalated Water in Li-saponite

1997 ◽  
Vol 52 (12) ◽  
pp. 863-866 ◽  
Author(s):  
Shin'ichi Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Time ◽  
Nmr Spectra ◽  
Hydration Shell ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Rotational Freedom

The dynamics of intercalated water molecules in Li-saponite was studied by measurement of solid state 2H and 7Li NMR spectra and of the 2H spin-lattice relaxation time at 175 ~ 350 K. Only a single component was observed in the 2H spectra above 260 K, suggesting that the water hydrogens rapidly exchange their positions between various distinct environments. Analysis of the observed spectra suggests that the water molecules possess C2 rotational freedom at around 260 K and that the hydration shell around Li+ cations is highly symmetrical in the same temperature region

Nuclear Magnetic and Quadrupole Resonance Studies of Phase Transitions in Crystalline (NH4)2SbF5 and (ND4)2SbF5

1988 ◽  
Vol 43 (3) ◽  
pp. 233-238 ◽  
Author(s):  
Ataru Kobayashi ◽  
Yoshichika Yoshioka ◽  
Nobuo Nakamura ◽  
Hideaki Chihara
Keyword(s):  
Activation Energy ◽  
Phase Transitions ◽  
Transition Point ◽  
Spin Lattice Relaxation ◽  
Ammonium Ion ◽  
Temperature Phase ◽  
Lower Phase ◽  
Resonance Frequencies ◽  
Quadrupole Resonance ◽  
Lower Transition

(NH4)2SbF5 undergoes two successive phase transitions at 169 and 292 K, both of which are of typical lambda-type and without thermal hysteresis. Proton and fluorine spin-lattice relaxation time measurements showed that the isotropic reorientation of the NH4+ ions is highly excited below the lower transition point with an activation energy of 15.5 kJ mol-1 and that the uniaxial reorientation of the square pyramidal SbF52- anion is excited above about 200 K with an activation energy of 42.0 kJ mol-1. There is strong cross relaxation between the proton and the fluorine over the whole temperature range of the measurements. The 121Sb and 123Sb nuclear quadrupole resonance frequencies show an anomalous temperature dependence; each resonance frequency assumes a minimum at around 100 K and increases on heating, reaches a maximum at the lower transition point, decreases drastically in the middle temperature phase and then fades out just below the upper transition point. The anomalous increase in the resonance frequencies stems from the reorganization of the N - H ... F type hydrogen bonds with the progress of the lower phase transition. The lower and the upper transition temperatures shift to 173.0 and 290.1 K, respectively, on deuteration of the ammonium ion.

scholarly journals 15N and 133Cs Solid NMR Studies on Ionic Dynamics in Plastic CsNO2

1996 ◽  
Vol 51 (5-6) ◽  
pp. 761-768 ◽  
Author(s):  
H. Honda ◽  
M. Kenmotsu ◽  
N. Onoda-Yamamuro ◽  
H. Ohki ◽  
S. Ishimaru ◽  
...  
Keyword(s):  
Phase Ii ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Nmr Studies ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Solid Nmr ◽  
Plastic Phase

The temperature dependence of the 15N and 133Cs NMR spin-lattice relaxation times, the 15N spin-spin relaxation time, and the 15N and 133Cs spectra of CsNO2 was observed in the plastic phase (209.2 < T < 673 K (m. p.)) and the low-temperature phase (Phase II). In Phase II we found the NO-2 180°-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 15N and 133Cs spectra in this phase are inconsistent with the reported crystal structure R3̅m 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 NO-2 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.

H NMR Study of Ionic Motions in High Temperature Solid Phases of (CH3NH3)2ZnCl4

2000 ◽  
Vol 55 (3-4) ◽  
pp. 412-414 ◽  
Author(s):  
Hiroyuki Ishida
Keyword(s):  
Activation Energy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

Abstract The reorientation of the tetrahedral complex anion ZnCl42- and the self-diffusion of the cation in (CH3NH3)2ZnCl4 were studied by 1H NMR spin-lattice relaxation time (1H T1) experiments. In the second highest-temperature phase, the temperature dependence of 1H T1 observed at 8.5 MHz could be explained by a magnetic dipolar-electric quadrupolar cross relaxation between 1H and chlorine nuclei, and the activation energy of the anion motion was determined to be 105 kJ mol -1 . In the highest-temperature phase, the activation energy of the self-diffusion of the cation was determined to be 58 kJ mol -1 from the temperature and frequency dependence of 1H T1

Nuclear magnetic resonance studies of the methylammonium hexahalotellurates

1992 ◽  
Vol 70 (3) ◽  
pp. 849-855 ◽  
Author(s):  
Mark R. MacIntosh ◽  
Marco L. H. Gruwel ◽  
Katherine N. Robertson ◽  
Roderick E. Wasylishen
Keyword(s):  
Line Shape ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Solid Phase ◽  
Variable Temperature ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
H Nmr ◽  
Nmr Study ◽  
Correlated Motion

A 2H and 14N NMR study of the solid methylammonium hexahalotellurates, (MA)2TeX6 (MA = CH3ND3+ or CD3NH3+, X = Cl, Br, and I), has been undertaken to characterize the dynamics of the methylammonium (MA) ion as a function of temperature. At room temperature, the MA ion in the hexachlorotellurate (solid II) is confined to C3 jumps about the C—N axis while a small angle libration of the C—N axis is occurring. In the room temperature phase, solid I, of (MA)2TeBr6 and (MA)2TeI6 the MA ions are performing overall reorientations on the ps time scale, averaging the 2H nuclear quadrupolar interactions to zero. Variable temperature 2H NMR spin-lattice relaxation times, T1, indicate an activation energy, EA, for "isotropic" reorientations of the CH3ND3+ ion of 5.2 ± 0.5 and 2.6 ± 0.3 kJ mol−1 for X = Br and I, respectively. Deuterium T1 values for C-deuterated MA ion in the hexaiodotellurate indicate an EA for whole-ion reorientation of 3.1 ± 0.3 kJ mol−1. At any given temperature, the correlation time, τc, derived from the T1 results was found to be the same for the two deuterium-labelled hexaiodotellurates. The similarity of both the EA and the τc values implies correlated motion of the methyl and ammonium groups. The 14N T1 results for solid I of (MA)2TeI6 indicate that C—N axis motions, with an EA = 5.6 ± 0.6 kJ mol−1, are more hindered than N—D or C—D bond dynamics. The 2H NMR spectra for (MA)2TeI6 (solid II) and (MA)2TeBr6 (solids II, III, and IV) are characterized by a Pake doublet line shape. The measured peak-to-peak splittings are less than what is predicted by C3 motion about the molecular symmetry axis. It is possible to model these line shapes by postulating that C3 rotations of the methyl and ammonium groups occur as the C—N axis librates in an effective cone about the position of the static molecular axis. For (CH3ND3)2TeBr6 and (CD3NH3)3TeBr6 the peak-to-peak splittings in the 2H NMR spectra were measured as a function of temperature in solid phases II, III, and IV and were found to be similar. Finally, the 2H NMR line shape relaxation for (MA)2TeBr6 (solid III) displays an orientation dependence indicating that rotations about the C—N axis are discrete rather than diffusive in nature. For solid phase II of (MA)2TeCl6, the line shape is observed to relax isotropically, implying that continuous C3 rotations are taking place. Keywords: 2H and 14N NMR, methylammonium hexahalotellurates, molecular motion.

85,87Rb, 14N NMR Studies of Successive Phase Transitions and Incommensurate Phase in R2Pb[Cu(NO2)6] (R = NH4, Rb)

2002 ◽  
Vol 57 (6-7) ◽  
pp. 403-407 ◽  
Author(s):  
Hiroyuki Ishikawa ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Relaxation Time ◽  
Phase Ii ◽  
Nmr Spectra ◽  
Lattice Relaxation ◽  
Quadrupole Coupling Constant ◽  
Lattice Relaxation Time ◽  
Incommensurate Phase ◽  
Spin Lattice Relaxation ◽  
Phase Iii ◽  
Nmr Studies

85,87Rb and 14N NMR spectra and spin-lattice relaxation time (T1) were measured for R2Pb[Cu(NO2)6] (R = Rb, NH4). The quadrupole coupling constant (e2Qq/h), asymmetry parameter (η), and the effective transverce relaxation time (T2) were estimated from the simulation of NMR spectra. The NMR spectra in commensurate phase III can be explained by the superposition of two components corresponding to two inequivalent sites of the R+ ion. In the incommensurate phase II, e2Qq/h and T2 decreased with increasing temperature, while was almost temperature independent. T1 in phase II is found to be determined by the contribution of acoustic phason with multi-soliton limits

X-ray Absorption and NMR Studies of LiNiCoO2 Cathodes Prepared by a Participate Sol-Gel Process

1997 ◽  
Vol 496 ◽  
Author(s):  
S. Rostov ◽  
Y. Wang ◽  
M. L. denBoer ◽  
S. Greenbaum ◽  
C. C. Change ◽  
...  
Keyword(s):  
Line Width ◽  
Sol Gel ◽  
Transition Metal Ions ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Teller Distortion ◽  
X Ray ◽  
Sol Gel Process ◽  
X Ray Absorption ◽  
Absorption Measurements

AbstractWe have synthesized lithiated nickel oxide-based cathode materials containing stoichiometric and excess lithium using a new low temperature colloidal paniculate sol-gel process. The process yields a xerogel precursor that transforms to the crystalline oxide at 800 °C in 2h. We studied the Li environment with nuclear magnetic resonance (NMR) and that of the transition metal ions with x-ray absorption spectroscopy. We measured samples of LiNi1−xCoxO2, with x = 0 and 0.25. The effect on each composition of the incorporation of 5 mol % Li was also examined. The precursor material appears to have no Ni3+, as indicated x-ray absorption measurements, and is highly disordered, showing little sign of interatomic correlations beyond the nearest neighbor in extended x-ray absorption fine structure (EXAFS) spectra. The 7Li NMR line widths and spin-lattice relaxation (T1) behavior are dominated by strong interactions with the paramagnetic Ni3+. The presence of 5 % excess Li causes almost no change in NMR line width or T1 in the mixed (Ni/Co) cathode, but does produce an almost 30% reduction in line width for the pure LiNiO2, implying that Co stabilizes the structure. The near-edge x-ray absorption measurements show the local Ni environment is relatively unaffected by Co substitution, a result confirmed by EXAFS analysis. The heat-treated samples are highly ordered, and both the near-edge and extended analysis imply Co substitutes primarily for Ni2+, not Ni3+. The Jahn-Teller distortion is apparent in both the stoichiometric and Li-excess materials.

2H NMR Study on Phase Transitions and Crystal Dynamics of p-Chloro- and p-Bromobenzyl Alcohols

2002 ◽  
Vol 57 (6-7) ◽  
pp. 388-394 ◽  
Author(s):  
Motohiro Mizuno ◽  
Masanori Hamada ◽  
Tomonori Ida ◽  
Masahiko Suhara ◽  
Masao Hashimoto
Keyword(s):  
Relaxation Time ◽  
Phase Transitions ◽  
Nmr Spectra ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Hydrogen Atoms ◽  
Potential Wells ◽  
H Nmr ◽  
Nmr Study ◽  
Crystal Dynamics

Two phase transitions of 4-chlorobenzyl alcohol (pCBA) and 4-bromobenzyl alcohol (pBBA), from the low-temperature phase (LTP) to the intermediate-temperature phase (ITP) and from ITP to the room-temperature phase (RTP), were investigated by 2H NMR and differential scanning calorimetry (DSC). The crystal dynamics in each phase were studied using the 2H NMR spectra, the spin-lattice relaxation time (T1) and the relaxation time of quadrupole order (T1Q) for the samples, where the hydrogen of the -OH group was selectively deutrated. The 2H NMR 1 of both crystals in the RTP were dominated by the fluctuation of the electric field gradient at 2H nucleus caused by vibrational motions of the -CH2OH group. In the LTP of both crystals, the fast jump of hydrogen atoms between the two sites corresponding approximately to the positions of the hydroxyl hydrogen atoms in the RTP and LTP were found from 2H NMR spectra. The results of T1 and T1Q in the LTP revealed that the jump of hydrogen atoms occurs in asymmetric potential wells and that these potential wells gradually approach symmetric ones with increasing temperature on the high-temperature side in the LTP

1H NMR Studies on Cationic Motions in Solid tert-Butylammonium Hexachlorostannate (IV)

1992 ◽  
Vol 47 (10) ◽  
pp. 1087-1090
Author(s):  
Hiroyuki Ishida ◽  
Tatsuo Higashiyama ◽  
Naomi Hayama ◽  
Ryuichi Ikeda
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Temperature Dependences

AbstractThe temperature dependences of the 1H spin-lattice relaxation time (T1) and the second moment (M2) of NMR absorptions were measured for anhydrous tert-butylammonium hexachlorostannate(IV) and its partially deuterated analogs [(CD3)3CNH3]2SnCl6 and [(CH3)3CND3]2SnCl6. Three kinds of cationic motions were revealed: the reorientations of the CH3 group about their C - C bonds, the NH+3 group about its C - N bond, and the tert-butyl group about the C - N bond. Their motional parameters were determined. Among the three motions, the NH+3 motion occurs at the lowest temperature with quite a small activation energy (9.9-10.0 kJ mol-1 ) .

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