Proton NMR Study of the Molecular Reorientation in the Trigonal Phase of Sodium Hydrosulfide

1974 ◽  
Vol 52 (23) ◽  
pp. 2370-2378 ◽  
Author(s):  
Kenneth R. Jeffrey
Keyword(s):  
Resonance Line ◽  
Relaxation Times ◽  
Spin Lattice Relaxation ◽  
Proton Nuclear Magnetic Resonance ◽  
Trigonal Axis ◽  
Molecular Reorientation ◽  
Sodium Hydrosulfide ◽  
Second Moment ◽  
Nmr Study ◽  
Trigonal Phase

The second moment of the proton nuclear magnetic resonance line and the spin–lattice relaxation time were measured as functions of temperature throughout the trigonal phase of NaSH. Motional narrowing of the resonance line occurs at about 120 K. A T1 minimum was also observed indicating molecular reorientation of the SH− ion. The second moment and the relaxation times were calculated using several models for possible SH− ion motion. The best agreement with experimental results was obtained when the proton was considered to move between two positions either side of the sulfur atom along the trigonal axis.

Molecular reorientation in sodium hydrosulfide: a deuterium nmr study

1981 ◽  
Vol 59 (11) ◽  
pp. 1585-1591 ◽  
Author(s):  
Kenneth R. Jeffrey ◽  
Roderick E. Wasylishen
Keyword(s):  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Trigonal Axis ◽  
Cubic Phase ◽  
Deuterium Nmr ◽  
Molecular Reorientation ◽  
Sodium Hydrosulfide ◽  
Nmr Study

Deuterium nmr provides a unique opportunity to verify that the molecular motion in sodium hydrosulfide, NaSH, in the trigonal phase is the flipping of the SH− ion between two positions parallel and antiparallel to the trigonal axis. Measurements of the spin–lattice relaxation time show that motion of the hydrosulfide ion is not influenced substantially by deuteration. Measurements of the deuterium nuclear quadrupole splitting, ΔνQ, over the range of temperatures where the correlation time, τc, describing the motion changes from [Formula: see text] show little change. The molecular motion of the SD− ions must, therefore, not change the deuterium quadrupolar interaction and 180° flipping of the SD− ion is the only reasonable model which fits this criterion.Spin–lattice relaxation times have also been measured in the high temperature cubic phase. At 376 K, τc was found to be 0.40 ps in agreement with neutron quasielastic scattering measurements.

A 2D deuterium NMR study of molecular reorientation in (CH3)3E+X- onium salts

2000 ◽  
Vol 78 (1) ◽  
pp. 46-50
Author(s):  
Andrew M Wachner ◽  
Kenneth R Jeffrey ◽  
Glenn H Penner
Keyword(s):  
Rotation Axis ◽  
General Structure ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Deuterium Nmr ◽  
Two Dimensional ◽  
Molecular Reorientation ◽  
Nmr Study ◽  
Onium Salts

Two dimensional deuterium NMR measurements are reported for three different onium salts (CH3)3SeNO3-d3, (CH3)3TeI-d3, and (CH3)3SI-d9. In these molecular solids with the general structure (CH3)3E+X-, three methyl groups are attached to the E atom. There is the possibility of reorientation of the methyls about their C3 axes and reorientation of the whole tri-methyl group about the C'3 axis. From an analysis of the 2D NMR exchange spectra the angle between the E-C bonds and the rotation axis for trimethyl reorientation were determined. Exchange rates and spin lattice relaxation times are given for several temperatures, to show how the mixing times for the experiments were selected. The data presented for (CH3)3TeI-d3, demonstrate that 2D techniques are sensitive to motions on a time scale an order of magnitude slower than that accessible using 1D line shape techniques.Key words: deuterium NMR, molecular motion, onium salts, two dimensional spectra.

1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

1995 ◽  
Vol 50 (8) ◽  
pp. 742-748 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien­ tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

A nuclear magnetic resonance investigation of n -pentane, n -hexane and cyclo pentane

1954 ◽  
Vol 222 (1151) ◽  
pp. 526-541 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Kcal Mole ◽  
Second Moment ◽  
Spin Lattice ◽  
Second Moments

The nuclear magnetic resonance spectra and spin-lattice relaxation times have been measured for the protons in n -pentane (C 5 H 12 ), n -hexane (C 6 H 14 ) and cyclo pentane (C 5 H 10 ) all in the solid state. The temperature range covered was from 70° K to the melting-points of 143·4° K for n -pentane, 177·8° K for n -hexane and 179·4° K for cyclo pentane. In the case of n -pentane and n -hexane the second moments of the absorption lines were found to be smaller than the computed rigid lattice values over the. whole temperature range. Possible molecular motions which might cause this reduction are discussed. It is suggested that the most probable type of motion is reorientation of the methyl groups at the ends of each molecule about the adjacent C—C bonds. An analysis of the spin-lattice relaxation times shows that this reorientation process is governed by an activation energy of 2·7 kcal/mole for n -pentane and 2·9 kcal/mole for n -hexane, values which support the mechanism postulated. At the lowest temperature the absorption lines had not reached their full widths, even though the reorientation frequencies at these temperatures were considerably less than the line-widths. The experimental second moment for cyclo pentane below about 120° K indicates that the lattice is effectively rigid in this temperature region. The uncertainties in both the experimental and theoretical second moments do not allow a distinction to be drawn between the plane and puckered molecular models. At the temperature of the first transition (122·4° K) the line-width second moment and relaxation time all show a sudden decrease. The low value of second moment at the higher temperatures indicates that considerable molecular motion is occurring, the molecules rotating with spherical symmetry. The change in crystal structure at the temperature of the second transition (138·1° K) is thought to be a direct result of this spherical symmetry. As the temperature increases, the results indicate that more molecular motion must be occurring, and it is thought that the rotating molecules are diffusing through the lattice.

1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate

1996 ◽  
Vol 51 (9) ◽  
pp. 991-996 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
High Mobility ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Wide Range ◽  
Deuterated Analogue

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.

Proton NMR Study of Molecular Dynamics in Hydrazinium Perchlorate

1990 ◽  
Vol 45 (2) ◽  
pp. 102-106
Author(s):  
K. Ganesan ◽  
R. Damle ◽  
J. Ramakrishna
Keyword(s):  
Molecular Dynamics ◽  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Temperature Minimum ◽  
Second Moment ◽  
Spin Lattice ◽  
Nmr Study

AbstractThe proton spin-lattice relaxation time T1 (at 5.4, 10 and 15 MHz) and second moment M2 (at 9.8 MHz) have been measured in hydrazinium Perchlorate (N2H5ClO4). The temperature dependence of T, shows two minima. The low temperature T, minimum has been explained in terms of NH3 reorientation about the N-N axis while the high temperature minimum is attributed to the exchange of protons within the NH2 group (180° flip about the H - N - H bisectrix). The activation energies for NH3 and NH: motions are found to be 20.5 kJ mol-1 and 39.8 kJ mol-1 , respectively. The second moment variation with temperature shows two transitions around 120 K and 210 K and has been discussed in terms of NH3/NH2 motions.

Bis(pyridine)difluoroboron, tris(pyridine)fluoroboron, and other (pyridine)haloboron cations. A systematic NMR study

1996 ◽  
Vol 74 (7) ◽  
pp. 1309-1320 ◽  
Author(s):  
Melvin J. Farquharson ◽  
J. Stephen Hartman
Keyword(s):  
Key Words ◽  
Diagnostic Test ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nmr Study

The adducts pyr•BF2Br and pyr•BFBr2 (pyr = pyridine) form fluoroboron cations by displacement of Br− by excess pyridine, the ease of cation formation being pyr2BF2+ » pyr2BFBr+ » pyr3BF2+•Cl− can be displaced from pyr•BF2Cl and pyr•BFCl2, but much less readily, to form pyr2BF2+, pyr2BFCl+, and, under forcing conditions, a few percent of pyr3BF2+. Non-fluorine-containing mixed boron trihalide adducts of pyridine also form haloboron cations by heaviest-halide-ion displacement, for example pyr•BClI2 giving pyr2BClI+, the ease of displacement always being I− > Br− > Cl−, and displacement always occurring more readily from mixed boron trihalide adducts than from unmixed-halogen adducts. The mechanistic implications of this are discussed. ortho Substituents greatly reduce the ability of pyridine to displace heavy halide ion, so 2-methylpyridine gives 2-Mepyr2BF2+ and 2-Mepyr2BFBr+ but not 2-Mepyr2BFCl+ or 2-Mepyr3BF2+, while 2,6-dimethylpyridine does not form any haloboron cations. 19F spin-lattice relaxation times of the fluoroboron cations are much shorter than those of neutral boron trihalide adducts in the same solution, and provide a further diagnostic test for their presence. Key words: fluoroboron cations, pyridines, mixed boron trihalide adducts, fluorine-19 NMR, boron-11 NMR.

Molecular Reorientation in the Plastic Crystalline Phase of Tris

1979 ◽  
Vol 32 (4) ◽  
pp. 905 ◽  
Author(s):  
RE Wasylishen ◽  
PF Barron ◽  
DM Doddrell
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Molecular Reorientation ◽  
Liquid Phase Transition ◽  
X Ray ◽  
Spin Lattice

Carbon-13 N.M.R. spectra of tris(hydroxymethyl)aminomethane (Tris) have been measured between 407 and 461 K. Proton-decoupled 13C N.M.R. spectra of solid Tris between 407 K and its melting point are relatively sharp (v� < 30 Hz) indicating rapid overall molecular reorientation in this temperature range. It was not possible to detect a 13C N.M.R, signal for Tris below 407 K. The observed 13C N.M.R. spin-lattice relaxation times appear continuous across the solid ↔ liquid phase transition. From the temperature dependence of T1, a rotational activation energy of 51.6 � 6 kJ mol-1 is calculated, which indicates that the molecules must expend considerable energy in reorienting. The N.M.R. results are discussed in relation to previous differential scanning calorimetry and X-ray diffraction data which indicate that Tris undergoes a solid ↔ solid transition at 407 K.

Interrelation Between Molecular Motions and Structure in Solid Trimethylamine-boron-trichloride as Studied by NMR

1992 ◽  
Vol 47 (11) ◽  
pp. 1157-1160
Author(s):  
S. Głowinkowski ◽  
, S. Jurga ◽  
E. Szcześniak
Keyword(s):  
Molecular Structure ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Molecular Motions ◽  
Boron Trichloride ◽  
Second Moment ◽  
Spin Lattice ◽  
Temperature Dependences

AbstractThe temperature dependences of proton second-moment and spin-lattice relaxation times (T1 and T1ρ) have been measured in solid (CH3)3NBCl3. The nature of reorientation processes occurring in the complex has been established and the activation parameters determined. The motions are discussed in relation to the molecular structure of the complex

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