Nuclear Zeeman and dipolar relaxation due to slow motion in aromatic single crystals

Lauer, O; Stehlik, D.; Hausser, Karl H.

doi:10.1016/0022-2364(72)90162-x

Cited by 13 publications

(11 citation statements)

References 8 publications

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“…The problem is overcome by transforming Zeeman order into dipolar order. The decay of dipolar order due to the time-dependent part of the dipolar interactions caused by molecule motion is then characterized by the relaxation time TID (Jeener and Broekaert, 1967;Lauer et al, 1972).…”

Section: Echoes In Solidsmentioning

confidence: 99%

Nuclear Magnetic Relaxation and the Biological Membrane

Lee

Birdsall

Metcalfe

1974

Methods in Membrane Biology

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Section: Echoes In Solidsmentioning

confidence: 99%

Nuclear Magnetic Relaxation and the Biological Membrane

Lee

Birdsall

Metcalfe

1974

Methods in Membrane Biology

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“…Jackson [34] observed a reorientational relaxation behaviour in norbomadiene without any evidence of librational relaxation even for much longer T1. Relaxation by paramagnetic impurities has been invoked in naphthalene [37] and biphenyl [38], but the relaxation times were much longer (-104 s) and the frequency dependence was not studied. It therefore appears that a detailed relaxation study at low temperature in such rigid organic molecules is still required before definite conclusions can be drawn.…”

Section: 22mentioning

confidence: 99%

Molecular motion in solid bicyclo[2.2.2]octane and bicyclo[2.2.2]oct-2-ene studied by nuclear magnetic resonance

et al. 1985

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“…The effects of substitution on the mobility of biphenyl derivatives have been discussed (Lauer, Stehlik & Hausser, 1972). Fluorine substitution seems to decrease the mobility; this may be due to changes in molecular shape or packing conditions.…”

Section: Biphenylmentioning

confidence: 99%

“…This molecule has been the object of experimental (Trotter, 1961;Hargreaves & Hasan Rizvi, 1962) and theoretical (Casalone, Mariani, Mugnoli & Simonetta, 1968) not completely understood (Lauer, Stehlik & Hausser, 1972); reorientation in the molecular plane, similar to that of the naphthalene derivatives, seemed likely, the molecule being planar in the crystal. Our calculations rule out this possibility, in view of the very high barrier implied; Fig.…”

Section: Biphenylmentioning

confidence: 99%

“…Also rotation around the other axis in the molecular plane is impossible, since the calculated barrier is extremely high. The experimentally detected rotational motion (Lauer, Stehlik & Hausser, 1972) must therefore be in the molecular plane, but the population of a hypothetical 180 ° minimum must be so low as not to be detected by X-ray analysis. Fig.…”

Section: Dipole-dipole Interaction Energiesmentioning

confidence: 99%

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Molecular rearrangements in organic crystals. II. The role of intermolecular cooperation and dipole–dipole interactions

Gavezzotti¹,

Simonetta²

1976

Acta Cryst Sect A

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A model to account for intermolecular cooperation during molecular rearrangements is described. A qualitative approach to electrostatic interactions is tested for some halogen-containing molecules.As a first step towards a better understanding of solidstate rearrangements of organic molecules, some potential-energy barriers to rigid-body rotations have been calculated in paper I (Gavezzotti & Simonetta, 1975), by the pairwise potential method. The qualitative, and in some cases quantitative, success of these simple calculations was considered an encouraging start to the application of the same method to more complex problems.The model that was built to perform these calculations (henceforth Model I) showed however some weak points. They are: (a) the crystal was built up of rigid, motionless molecules surrounding the one that undergoes a certain rearrangement, and (b) no electrostatic contribution was included in the calculations. The first point comes abruptly into play when large molecular displacements, such as those involved in phase transitions or solid-state reactions, are considered. The second, although very important in some cases, has presumably a smaller effect than the first. This paper is devoted to the description of a new model that can account for intermolecular cooperation, and, to a first approximation, for the electrostatic interactions in crystals of polar molecules. The molecular cluster model (Model II)If many molecules move at the same time in a crystal, it is no longer possible to evaluate the potential energy by summing the pairwise interactions of one molecule with the surrounding ones. The simplest way of accounting for energetic changes in this case is to consider a molecular cluster, made up of a finite number of molecules, and to calculate the pairwise interactions of each molecule with all other molecules in the cluster. Obviously, the 'energy' calculated in this way can never converge to a true lattice energy, and has no physical meaning in itself. However, differences in these cluster 'energies' reflect true energy changes in the crystal.A given rearrangement is considered to have a driving force, or main reaction coordinate, visualized as the evolution of one or more internal coordinates of one fundamental molecule. Then one or more other molecules in the cluster are allowed appropriate motions, with respect to which the cluster 'energy' is minimized. In this way a minimum-energy pathway is described from reactant to product through the multidimensional energy surface. In doing this, care must be taken that (a) the cluster is large enough to allow the calculation of a substantial amount of the barrier, and (b) no undue freedom is allowed to the molecules nearest to the fundamental one, as a result of truncation of the cluster. The cluster is therefore to be modelled in two shells, the first including the cooperating molecules, and the second to ensure that they experience much the same field as the fundamental one. The size of the first shell can be established by subdivision of ...

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Nuclear Zeeman and dipolar relaxation due to slow motion in aromatic single crystals

Cited by 13 publications

References 8 publications

Nuclear Magnetic Relaxation and the Biological Membrane

Nuclear Magnetic Relaxation and the Biological Membrane

Molecular motion in solid bicyclo[2.2.2]octane and bicyclo[2.2.2]oct-2-ene studied by nuclear magnetic resonance

Molecular rearrangements in organic crystals. II. The role of intermolecular cooperation and dipole–dipole interactions

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