Photophysical Constants of the Tetraoxa[8]Circulene Molecule

Abstract

The rate constants of photophysical processes (radiation rate constant, internal conversion rate constant, and quantum fluorescence yield) have been calculated for the tetraoxa[8]circulene molecule by the INDO/S, TDDFT, and CC2 methods. It is confirmed that the doubly degenerate triplet level Т₂ and the level Т₁ are located below the first singlet excited level S₁. According to the selection rules for the angular momentum, the spin-orbit interaction between the levels S₁ and T₁ (S₁ and T₂) is equal to zero. Therefore, the internal conversion is the only nonradiative channel in this molecule. The results of calculations also demonstrate that values of the internal conversion rate constant and the quantum fluorescence yield obtained by the INDO/S method are incorrect.