Vibronic interactions and Jahn-Teller effects in π-conjugated systems

We calculate vibronic coupling constants of the trianions of π-conjugated hydrocarbons such as benzene, [18]annulene, coronene, and corannulene which have high-symmetric geometries. High-frequency modes afford large vibronic coupling constant in the trianion of benzene. In the trianion of [18]annulene, on the other hand, the lowest frequency mode gives large coupling constant. Both low and high frequency modes afford large coupling constants in the trianion of coronene as if the electronic properties of benzene and [18]annulene still remain in coronene. The lowest two frequency modes give large coupling constants in the trianion of corannulene, and these coupling constants in corannulene trianion are much larger than those of coronene trianion.