Solvent Effect and Aromatic Compounds Magneto-Optic Properties

CRASNIER, J.-F. KERUZORE, and F. GALLAIS Laboratoire de Chimie de Coordination C.N.R.S., B.P. 4142, 31030 Toulouse, Cedex, France 

Nearly one hundred and twenty years have passed since Verdet formulated the laws of Faraday effect and particularly the relation existing between the Verdet Constant of a mixture and the constants of the components of this mixture [1] and since then a vast experimental evidence has shown that magneto-optic properties are effectively additive. 

We have found for our part that magnetic rotations additivity laws hold perfectly for liquid mixtures and for solutions when these have a normal rotatory dispersion and are studied far enough from their spectral absorption zone. This remains so true -as long as no chemical reaction occurs to modify molecular structures - that it is even possible to define sufficiently constant and additive bond rotations. 

Under such circumstances the exceptions offered by benzene and parent substances is remarkable. The striking magneto-optic properties of such molecules have already been reported before that audience in 1970 [2]. At that time we had been mainly concerned with the relations existing between these properties and the specific type of 7T delocalisation which occurs in such molecules and is responsible for their so-called aromatic character . 

From this general picture we only want now to retain and to comment the facts which establish that benzene and similar molecules depart from additivity laws when their magneto-optic rotation is measured in solutions, in a way which clearly indicates the existence of solvents effects. 

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SOLVENT EFFECT AND AROMATIC COMPOUNDS MAGNETO-OPTIC PROPERTIES... 

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