Anomalie der g-Faktoren symmetrisch phenylsubstituierter aromatischer Radikale

Abstract

For the phenylsubstituted hydrocarbon radicals of p-terphenyl, diphenylanthracene, rubrene, tetraphenylpyrene, and triphenylmethyl we have observed g-factors showing pronounced deviations from the values expected by Stone's g-factor theory. In some cases the deviations are as large as -1.6X10 -4 which cannot be explained in the frame of the conventional HMO conjugation model. A new model with additional consideration of a hyperconjugative coupling between the π-orbitals and the σ-orbitals of the twisted phenyl rings is presented which, in connection with certatin modifications of Stone's theory, explains the observed g-factor anomaly. Details of the hyperconjugative model of twisted phenyl rings are presented in a subsequent paper.