PHOTOPHYSICALLY RELEVANT POTENTIAL-ENERGY FUNCTIONS OF LOW-LYING SINGLET-STATES OF BENZENE, PYRIDINE AND PYRAZINE - AN ABINITIO STUDY

Potential energy functions of low-lying singlet states of benzene, pyridine, and pyrazine along the reaction path leading to the prefulvenic forms have been calculated with the UHF/STO-3G method. It is found that the electronic ground state of the prefulvenic form is adiabatically correlated to a valence excitation of the aromatic ring at the planar configuration (the S1 state in benzene, the S2 state in pyridine and pyrazine). Some consequences for the photophysical dynamics (channel-three-like behaviour) of azabenzenes are discussed.