Theoretical Studies of the Photochemical Behavior of Styrylquinoxaline

Theoretical Studies of the Photochemical Behavior of Styrylquinoxaline

The lowest excited state of styrylquinoxaline (StQx) has been studied by the SCF-MO-CI P-P-P and MM2 method. Results suggest that the lowest excited state is of a ${\pi},{\pi}^{\ast}(S_1$) nature with the n,${\pi}^{\ast}(S_2)$ state lying slightly above it. On the basis of these calculations the observed electronic spectra are discussed. The calculated absorption spectra are qualitatively similar to experimental ones with their characteristic visible bands. MM2 force field calculation suggested that the postulated conformers are different from each other in energy and planarity and are seperated by a barrier of about 4 Kcal/mole.