The Electronic Structure of the Fulvene Radical Cation

Abstract

Abstract The molecular and electronic structures of the unsubstituted fulvene radical cation, FV+·, were investigated by ab initio SCF calculations. The planar 2A2 state, which corresponds to removing an electron from the butadienic moiety in the five-membered ring, was found to be the ground state of FV+·, and is more stable than the planar 2B1 state, which corresponds to an olefin radical cation, by about 26 kcal mol−1. The barrier to rotation around the exocyclic C–C bond in the 2A2 radical cation was calculated to be about 63 kcal mol−1. The importance of electronic relaxation in substituted fulvene radical cations is discussed in connection with the rotational barrier.