A spin-lattice relaxation study of the molecular reorientation of 2-methylindole as a function of viscosity and complex formation

The viscosity (η) dependence of the 13C spin-lattice relaxation time (T1) of C-3 of 2-methylindole was investigated by changing the temperature (T) and by changing the solvent system. The observed η/T dependence of the effective reorientation correlation time (calculated from T1) is compared with those derived from theory based on hydrodynamic rotation with "stick" and with "slip" boundary conditions. This data implies that the reorientation of 2-methylindole obeys a near-slip condition in 1,2-dichloroethane. The 13C T1 of C-3 of 2-methylindole was also determined as a function of the fraction complexed with 1,3,5-trinitrobenzene (TNB) at 35 °C in 1,2-dichloroethane. The observed T1 in this case, depends on the rates of reorientation of the molecule in the free and the bound states, the rate of association of the molecules, the rate of dissociation of the complex, as well as increases in viscosity brought about by increases in the concentration of TNB. Analysis of the data, by application of the Anderson–Fryer formulation, gives a rate of reorientation in the bound state of 55 ns−1 at 35 °C and 0.69 cP as compared to a value of 150 ns−1 in the free state under the same conditions.

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A nuclear magnetic resonance investigation of three solid benzenes

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1953.0123 ◽

1953 ◽

Vol 218 (1135) ◽

pp. 537-552 ◽

Cited By ~ 208

Keyword(s):

Crystal Structure ◽

Nuclear Magnetic Resonance ◽

Relaxation Time ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Second Moment ◽

Spin Lattice ◽

Second Moments ◽

A Value

The nuclear magnetic resonance absorption spectrum and the spin-lattice relaxation time have been measured for the protons in three isotopic species of benzene in polycrystalline form between 75 and 278° K. The three species were C 6 H 6 , C 6 H 5 D and 1. 3. 5 - C 6 H 3 D 3 . For all three species the measured spectrum has its full rigid lattice width below 90° K. A method of analysis is developed which makes it possible to derive separately the intramolecular and the intermolecular contributions to the second moment (mean square width) of the spectrum from the measured second moments, without the necessity of knowing the crystal structure. From the intramolecular contribution it is found that the separation of neighbouring protons in the C 6 H 6 molecule is 2.495 ± 0.018 Å. The intermolecular contribution is in agreement with a value calculated from a knowledge of the crystal structure. On warming from 90 to 120°K the spectrum for all three species narrows considerably. From 120°K to the melting-point (278.7° K) the second moments remain almost constant. The second moment separation procedure is also applied in this range and leads to the conclusion that the narrowing is caused by reorientation of the molecules about their hexad axes in the crystal lattice. Analysis of the measurements of the spin-lattice relaxation time shows that for all three species the reorientation process is governed by an activation energy of 3.7 ± 0.2 kcal/mole. The reorientation frequency is of the order of 10 4 c/s at 85° K and rises to a value of the order of 10 11 c/s just below the melting-point. The relationship between the present experimental results and recent measurements of the Raman spectrum of solid benzene is discussed. Finally, consideration is given to the application to other materials of methods of separating the intra- and intermolecular contributions to the second moment.

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MOLECULAR REORIENTATION IN FERROELECTRIC LITHIUM HYDRAZINIUM SULPHATE

Canadian Journal of Physics ◽

10.1139/p67-272 ◽

1967 ◽

Vol 45 (10) ◽

pp. 3257-3263 ◽

Cited By ~ 11

Author(s):

W. D. MacClement ◽

M. Pintar ◽

H. E. Petch

Keyword(s):

Low Temperatures ◽

Room Temperature ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Resonance Absorption ◽

Spin Lattice Relaxation ◽

Kcal Mole ◽

Molecular Reorientation ◽

Hindered Rotation ◽

Spin Lattice

The temperature dependence of the spin-lattice relaxation time T1 and of the second moment of the magnetic-resonance absorption signal has been determined for protons in powdered lithium hydrazinium sulphate over the range 80–480 °K. These measurements indicate that the hydrazinium ion is rigid only at very low temperatures. As the temperature is raised, the −NH3 group begins to undergo hindered rotation about the N–N axis with an activation energy of 4.2 kcal/mole and the effect of this motion on the line width becomes pronounced in the region of 85 °K. Further molecular reorientation begins above room temperature and is probably reorientation of the −NH2 group about either the N–N axis or the bisectrix of the H–N–H angle. Above 435 °K the hydrazinium ion begins to tumble about several axes and at 480 °K diffuses through the structure.

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Rotational ordering and nuclear spin-lattice relaxation in solid methane

Canadian Journal of Physics ◽

10.1139/p78-157 ◽

1978 ◽

Vol 56 (9) ◽

pp. 1182-1189 ◽

Cited By ~ 21

Author(s):

G. Briganti ◽

P. Calvani ◽

F. De Luca ◽

B. Maraviglia

Keyword(s):

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Proton Spin ◽

Spin Lattice Relaxation ◽

Molecular Reorientation ◽

Spin Lattice ◽

Nuclear Spin Lattice Relaxation ◽

Special Cases ◽

Lower Temperature ◽

Lower Temperature Region

The proton spin-lattice relaxation time has been measured in solid CH4 down to 0.4 K. In the ordered phase at 9 < T < 20 K the relaxation process is induced by librons. The energy of the librons (~75 K) is in excellent agreement with the theoretical prediction by Yamamoto, Kataoka, and Okada. T1 has been found constant within experimental error between 0.4 and 9 K. The mechanism responsible for relaxation in this lower temperature region is attributed to the adiabatic molecular reorientation of the ordered T molecules. The cooling procedure has been found in special cases to affect the experimental results.

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A Nuclear Spin Relaxation Study of the Spin–Rotation Interaction in Spherical Top Molecules

Canadian Journal of Physics ◽

10.1139/p72-171 ◽

1972 ◽

Vol 50 (12) ◽

pp. 1252-1261 ◽

Cited By ~ 40

Author(s):

James A. Courtney ◽

Robin L. Armstrong

Keyword(s):

Lattice Relaxation ◽

Relaxation Mechanism ◽

Lattice Relaxation Time ◽

Spin Rotation ◽

Spin Lattice Relaxation ◽

Molecular Reorientation ◽

Effective Spin ◽

Spin Lattice ◽

Pass Through ◽

Rotation Constant

The spin–lattice relaxation time T1 of the 19F nuclei was measured in gaseous samples of CF4, SiF4, GeF4, and SF6 at room temperature for densities from 0.015 to 20 amagat. In each case T1 was observed to pass through a minimum for some density less than 0.50 amagat. In addition, T1 was measured in the extreme narrowing region for SF6 at 238, 265, 293, 313, and 349.5 K.. The spin–rotation interaction provides the dominant relaxation mechanism in all cases. The data are analyzed on the basis of the assumption that the collision modulated spin–rotation interaction may be described by a single correlation function which is a simple exponential function of time. Values of an effective spin–rotation constant and a cross section for molecular reorientation are obtained for each gas. Assuming the validity of the model used to analyze the relaxation data, the combination of nuclear magnetic relaxation results with molecular beam measurements yields more accurate values of the anisotropic spin–rotation constant Cd than have been previously available.

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NMR spin-lattice relaxation time T1calculation for molecular reorientation through inequivalent potential barriers in the case ofn-fold (n= 2, 3, 4, 6) symmetry axis

Molecular Physics ◽

10.1080/00268970802459504 ◽

2008 ◽

Vol 106 (20) ◽

pp. 2345-2356

Author(s):

Asja Kozak

Keyword(s):

Relaxation Time ◽

Symmetry Axis ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Spin Lattice Relaxation ◽

Molecular Reorientation ◽

Potential Barriers ◽

Spin Lattice Relaxation Time ◽

Spin Lattice

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Nuclear Magnetic Resonance Investigation of Possible Molecular Motion in Coronene, Perlene, and Triphenlene in the Solid State

Canadian Journal of Chemistry ◽

10.1139/v71-554 ◽

1971 ◽

Vol 49 (20) ◽

pp. 3332-3335 ◽

Cited By ~ 19

Author(s):

C. A. Fyfe ◽

B. A. Dunell ◽

J. Rimeester

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Molecular Structures ◽

Spin Lattice Relaxation ◽

Molecular Reorientation ◽

Spin Lattice ◽

Magnetic Resonance Investigation ◽

Nuclear Magnetic

Broad-line nuclear magnetic resonance (n.m.r.) and spin lattice relaxation time measurements on solid coronene indicate the presence of a molecular reorientation process at 160 °K. The activation energy for the process has been determined at 5.9 kcal/mol and the nature of the motion deduced as being reorientation in the plane of the molecule. No motional processes are observed for perylene or triphenylene.The results are discussed with respect to thermodynamic data and the molecular structures.

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Proton Spin Relaxation in Low Density CH4–He Mixtures

Canadian Journal of Physics ◽

10.1139/p74-119 ◽

1974 ◽

Vol 52 (10) ◽

pp. 876-879 ◽

Cited By ~ 3

Author(s):

Krovvidi Lalita

Keyword(s):

Cross Section ◽

Lattice Relaxation ◽

Lattice Relaxation Time ◽

Proton Spin ◽

Spin Lattice Relaxation ◽

Low Density ◽

Centrifugal Distortion ◽

Molecular Reorientation ◽

Density Region ◽

Spin Lattice

The spin lattice relaxation time T1 was measured in CH4–He mixtures at 298 K for two compositions in the density region where T1 goes through a minimum. The data were fitted taking the centrifugal distortion effects into account. The cross section for molecular reorientation due to CH4–He collisions was obtained.

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