Molecular deformations induced by liquid crystalline solvents

The elecrton resonance spectrum of the 2-trithienylmethyl radical has been recorded at several temperatures in both the isotropic and nematic phases of 4,4'-dimethoxyazobenzene. The temperature dpendence of the anysotropic hyperfine splitting constats in the nematic mesophase cannot be explained in terms of the increased alignment of the soilute molecule alone. A redistribution of spin density deriving from a solvent induced deformation of the radical seems to be responsible for the observed trend. Expressions for calculating the hyperfine tensor resulting from the dipolar interaction between a nucleus and an electron contained in a Slater 3pz orbital have been also derived, extending from the McConnel and Strathdee treatment.