Effect of magnetically anisotropic solvent molecules on nuclear screening

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Abstract
Expressions are derived for the effects of magnetically anisotropic discshaped or rod-shaped solvent molecules on the nuclear screening in a spherical solute molecule, using a model in which the solute and solvent molecules are represented respectively by a hard sphere and a disc or rod which interact only when they collide. The expressions are functions of the dimensions of the sphere and of the disc or rod, but are independent of the position within the solute molecule of the nucleus under observation. The predicted effects are compared with measurements of the differential solvent shift between carbon tetrachloride and benzene for the solutes methane, tetramethylsilane and cyclohexane. The model satisfactorily accounts for the qualitative dependence on the radius of the solute molecule, but predicts solvent shifts approximately twice as great as those observed. It is suggested that the discrepancy results from neglecting attractive van der Waals forces.