The Nature of Electronically Excited States and Photoprocesses in Psoralen Molecules and Their Complexes

The nature of electronically excited states of molecules of psoralens and their complexes with methanol and the photoprocesses occurring in the molecules under exposure to light were studied by quantum chemistry methods. It was found that the principal deactivation pathway for all of the compounds examined is intersystem (S–T) crossing, which substantially affects their properties as sensitizers. It was shown that isomerization and substitution of the methoxy group do not lead to significant enhancement of the S–T transition.