Oxygen quenching of excited singlet and triplet states of polycyclic aromatic hydrocarbons in the vapor phase

The quenching rate constants of excited singlet (kSO2) and triplet (kTO2) states by oxygen were investigated in the vapor phase for polycyclic aromatic hydrocarbons having distinguishing oxidation potentials Eox. The significant spread in the rate constants was found (4 × 105 s−1 Torr−1 < kSO2 < 1.2 × 107 s−1 Torr−1; 5 × 102 < kTO2 < 4 × 105 s−1 Torr−1). The values of both kSO2 and kTO2 change linearly in the logarithmic scale with free energy change for complete electron transfer ΔGET, which points that the charge-transfer interactions are involved in the oxygen quenching of the S1 and T1 states.