Homoconjugation in Radical Cations

Recent studies of nuclear spin polarization effects in cyclopropane derivatives have provided considerable information on the structure as well as the spin and charge density distributions in this class of radical ca,tions. In the present work we report an extension of the frontier MO/perturbation MO theory of homoconjugation to include such species in an attempt to rationalize further the experimental results mentioned above, and to provide guidelines for understanding the structures of radical cations derived from other types of cyclopropane derivatives. The structures observed for the radical ca'1:ions of diphenylcyclopropane, trimethylcyclopropane, and benzonorcaradiene are rationalized, and the structures of the radical cations of spirocyclopropanefluorene and vicinally cyclopolyene-substituted cyclopropanes are predicted.