Dynamic Behavior of Group 13 Elements in Bromocomplexes as Studied by NQR and NMR

2000 ◽  
Vol 55 (1-2) ◽  
pp. 117-123 ◽  
Author(s):  
Yasumasa Tomita ◽  
Hiroshi Ohki ◽  
Koji Yamada ◽  
Tsutomu Okuda
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Group 13 ◽  
Spin Lattice ◽  
Temperature Dependences

NMR, NQR, powder X-ray diffraction, DTA and AC conductivity were measured in RMBr4 (R = Ag, Cu; M = Al, Ga) and RM2Br7 (R = Li, Ag; M = Al, Ga). In RMBr4 , the activation energy of Cu+ diffusion was evaluated from 63Cu NMR and was in good agreement with that from 81Br NQR. In CuAlBr4 , the e2Qq/h value of 63Cu NMR and the η value of 27AI NMR changed linearly with decreasing temperature, although the e2Qq/h value of 27AI NMR did not change so much. These temperature dependences are supposed to be due to Cu+ diffusion and not to a variation of the lattice constants. In RM2Br7 , the activation energy was obtained from the spin-lattice relaxation time T1 of 81Br NQR and is ascribed to a modulation of the cation diffusion. The line width of 7Li NMR in LiAl2Br7 was about 5.9 kHz in the low-temperature phase and 0.4 kHz for the high-temperature phase. The 27AlNMR spectrum was broadened by the quadrupole interaction and unchanged up to 400 K, suggesting that diffusion of Li+ ions occurs in the high-temperature phase.

Phase transitions and molecular motions in adamantane derivatives: 1-adamantanol

1987 ◽  
Vol 65 (8) ◽  
pp. 1757-1760 ◽  
Author(s):  
Pierre D. Harvey ◽  
Denis F. R. Gilson ◽  
Ian S. Butler
Keyword(s):  
High Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Adamantane Derivatives ◽  
Hydroxyl Groups ◽  
Temperature Phase ◽  
Spin Lattice

An order–disorder transition occurs in 1-adamantanol at 359 K on heating and at 342 K on cooling, with transition entropies of 36 and 34 J K−1 mol−1, respectively. FT-ir spectra show that free hydroxyl groups exist in the high temperature phase, but the majority of the O—H groups remain hydrogen bonded. The barrier to adamantyl group rotation in the low-temperature phase, determined from proton spin–lattice relaxation time measurements, is 20.9 Kj mol−1, and the barrier to rotation in the high-temperature phase is 35.0 kJ mol−1.

1H Nmr Study Of Molecular Motions In Thiourea Pyridinium Nitrate Inclusion Compound

2004 ◽  
Vol 59 (7-8) ◽  
pp. 505-509 ◽  
Author(s):  
M. Grottela ◽  
A. Kozak ◽  
A. Pajzderska ◽  
W. Szczepański ◽  
J. Wąsicki
Keyword(s):  
Inclusion Compound ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Spin Lattice ◽  
Nmr Study ◽  
Pyridinium Cations

The proton NMR second moment and spin-lattice relaxation time have been studied for polycrystalline thiourea pyridinium nitrate inclusion compound and its perdeuderated analogues in a wide temperature range. The reorientation of two dynamically different pyridinium cations around their pseudohexagonal symmetry axis taking place over inequivalent barriers have been revealed in the low-temperature phase. Activation parameters for these motions have been derived. A symmetrization of the potential barriers has been observed at the transition from intermediate to the high temperature phase. The motion of thiourea molecules has been also evidenced, but could not be unambiguously described.

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

1H and 19F NMR Study of Ammonium Ion Motion in Ammonium Trifluorostannate (II)

1988 ◽  
Vol 43 (2) ◽  
pp. 187-188
Author(s):  
Kiyofumi Hirokawa ◽  
Yoshihiro Furukawa
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Ammonium Ion ◽  
Ion Motion ◽  
Spin Lattice ◽  
Nmr Study ◽  
Temperature Dependences

Abstract The temperature dependences of the second moment and spin-lattice relaxation time of 1H and 19F NMR were measured on ammonium trifluorostannate (II) NH4SnF3. It was found that the NH4+ ions having a C3 symmetry in the crystal undergo overall reorientations with an activation energy of 22 kJ mol - 1.

A Proton NMR Study of n-Decylammonium Chain Dynamics in the Perovskite-type Layered Compound (C10H21NH3)2CdCl4

1993 ◽  
Vol 48 (4) ◽  
pp. 563-569 ◽  
Author(s):  
Stefan Jurga ◽  
Kazimierz Jurga ◽  
Eduard C. Reynhardt ◽  
Piotr Katowski
Keyword(s):  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Layered Compound ◽  
Temperature Phase ◽  
Potential Wells ◽  
Spin Lattice ◽  
Compound C ◽  
Nmr Study

Abstract A detailed proton second moment and spin-lattice relaxation time investigation of the bilayered compound (C10H21NH3)2 CdCl4 is reported. In the low temperature phase the methyl group exe-cutes a classical threefold reorientation, while the NH3 group is involved in a similar reorientation in an asymmetric potential well. Evidence for defect chain motions in this phase has been found, and infomation regarding the potential wells associated with these motions has been extracted from the data. In the high temperature phase, slow chain defect motions and fast fourfold reorientations of chains about their long axes, parallel to the normal to the bilayer, have been observed.

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 ) .

Motions of Methylammonium Ions in (CH3NH3)2ZnBr4 Crystals Studied by 1H NMR and Thermal Measurements

1990 ◽  
Vol 45 (7) ◽  
pp. 923-927
Author(s):  
Hiroyuki Ishida ◽  
Kentaro Takagi ◽  
Tadashi Iwachido
Keyword(s):  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Self Diffusion ◽  
Spin Lattice ◽  
H Nmr

AbstractMeasurements of the 1H spin-lattice relaxation time T1, the linewidth parameter T*2the second moment of 1H NMR absorption, differential thermal analysis, and differential scanning calorimetry were performed on methylammonium tetrabromozincate(II) crystals from 58 to above 500 K. A solid-solid phase transition was located at 456 K. In the room temperature phase, 120° reorientational jumps of CH3 and NH3+ groups in the cation about its C -N bond axis were detected. In the high-temperature phase, the cations undergo overall reorientation as well as translational self-diffusion. The activation energy for the cationic self-diffusion was evaluated to be 18 kJ mol-1 .

Nuclear magnetic resonance studies of molecular motion in guanidinium chloride, bromide, and iodide

1985 ◽  
Vol 63 (6) ◽  
pp. 1239-1244 ◽  
Author(s):  
Christopher I. Ratcliffe
Keyword(s):  
High Temperature ◽  
Molecular Motion ◽  
Lattice Relaxation ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fold Axis ◽  
Guanidinium Chloride ◽  
Spin Lattice ◽  
H Nmr

Guanidinium [Formula: see text] chloride, bromide, and iodide salts have been studied by 1H and 2H nmr as a function of temperature. The 2H powder lineshapes show conclusively that reorientation of the guanidinium ion occurs about the principal three-fold axis in the chloride, bromide, and high temperature phase of the iodide. Activation energies for this process have been obtained from 1H spin-lattice relaxation results. The question of whether or not there are concurrent two-fold flips of the —NH2 units is discussed, but must presently remain unresolved. It was found that the high temperature phase of the iodide can be supercooled.

Cation and Anion Reorientation at Phase Transition in Pyridinium Tetrafluoroborate

1990 ◽  
Vol 45 (1) ◽  
pp. 33-36 ◽  
Author(s):  
J. Wąsicki ◽  
Z. Pająk ◽  
A. Kozak
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Temperature Dependences

AbstractTemperature dependences of 1H and 19F second moment and spin-lattice relaxation times for polycrystalline pyridinium tetrafluoroborate were measured. A phase transition was discovered at 202 K. A model of cation reorientation between inequivalent (low-temperature phase) and equivalent (high-temperature phase) equilibrium positions is proposed. Whether the anion reorients isotropically or about a symmetry axis cannot be decided. An analysis of cross-relaxation effects yielded activation parameters for cation and anion reorientation. The rotational correlation times for both ions converge just at the phase transition reaching the value of 10-10s.

scholarly journals Cationic Dynamics in the Crystalline Phases of (CH3NH3)PbX3 (X: Cl, Br) as Studied by Proton Magnetic Resonance Techniques

1989 ◽  
Vol 44 (11) ◽  
pp. 1122-1126 ◽  
Author(s):  
Yoshihiro Furukawa ◽  
Daiyu Nakamura
Keyword(s):  
Room Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Anomalous Behavior ◽  
Spin Lattice Relaxation ◽  
Rotational Relaxation ◽  
Temperature Phase ◽  
Spin Lattice ◽  
H Nmr ◽  
Temperature Dependences

The temperature dependences of the 1H spin-lattice relaxation time T1, the linewidth parameter T2*. and the second moment M2 of 1H NMR absorption were measured for solid (CH3NH3)PbX3 (X: CI. Br). In the room-temperature cubic phases of both salts, and also in the high-temperature tetragonal phase of (CH3NH3)PbBr3, the cations undergo rapid overall rotation or reorientation. In the lowest-temperature phase of both salts the orientation of the cations is fixed but rapid C3 reorientation of the CH3 and NH+3 groups of the cations about their C - N bond axes takes place. From the M2 measurements, a precessional motion of the cations in the intermediate-temperature phase of both complexes is suggested. Above room temperature, 1H T1 of both salts can be explained by assuming spin-rotational relaxation operative due to the rapid rotation of the cations. An anomalous behavior of 1H T1, attributable to cross relaxation between 1H and 81Br nuclei, was detected for (CH3NH3) PbBr3 when T1 was measured at 42 MHz

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