Photophysical Constants of the Tetraoxa[8]circulene Molecule
Calculations of rate constants of photophysical processes (radiation rate constant, internal conversion rate constant, and quantum fluorescence yield) have been performed for the tetraoxa[8]circulene molecule by the INDO/S, TDDFT, and CC2 methods. It is confirmed that the doubly degenerate triplet level Т <sub>2</sub> and the level Т <sub>1</sub> are located below the first singlet excited level S <sub>1</sub>. According to the selection rules for the angular momentum, the spin-orbit interaction between the levels S <sub>1</sub> and T <sub>1</sub> ( S <sub>1</sub> and T <sub>2</sub>) is equal to zero. Therefore, the internal conversion is the only nonradiative channel in this molecule. The results of calculations have also shown that values of the internal conversion rate constant and the quantum fluorescence yield obtained by the INDO/S method are incorrect.