[18]Annulene: a benzene-like S_0/S_1 conical intersection located with CASSCF + GVB

摘要

A further parallel between the planar annulene and benzene has been demonstrated: the existence of a topologically equivalent S_0/S_1 conical intersection. The lowest energy point on the crossing has been optimized with the MMBV and CASSCF + GVB/4-31G methods. These calculations suggest that fluorescence might be observed from the S_1 state of annulene, and that this would disappear at higher vibrational excess energies as a route to efficient non-radiative decay via the conical intersection became accessible (the 'channel 3' mechanism for benzene).