Deutung der g-Faktor-Anomalie symmetrisch phenylsubstituierter aromatischer Radikale mit Hilfe eines Hyperkonjugationsmodells

Abstract

Abstract In a preceding paper we reported on anomalous g-factors of some phenyl-substituted hydro-carbon radicals which show deviations in the order of -1X10-4 from the values predicted by Stone's g-factor theory. This anomaly cannot be explained in the frame of the conventional HMO conjugation model. In this paper we present an explanation of this anomaly which is based on a hyperconjugative coupling between the π-orbitals and the phenyl-σ-orbitals coming into effect by the twisting of the sterically hindered phenyl rings. The predominant effect leading to the observed general reduction of the g-factors is caused by the spin density migration into the phenyl-σ-plane where g-factor considerably smaller than in pure π-systems.