Triplet state generation followed by the excited-state intramolecular proton transfer in 3-sulfanylchromen-4-one

We theoretically study the triplet formation dynamics of tautomers associated with the excited-state intramolec-ular proton transfer of 3-sulfanylchromen-4-one (3-SC). The S1-T3 intersystem crossing pathway is expected to compete with the intramolecular thiol proton transfer upon photoexciting the normal tautomer (parent molecule) to its S1 state. The triplet formation via the S ' 1-T ' 2 intersystem crossing tends to be the dominant nonradiative process in the proton-transferred tautomer. The wavepacket transfer to the respective accessible receiver triplet state is more pronounced in the proton-transferred tautomer than its parent tautomer, implying an efficient triplet formation followed by the proton transfer via S1 in 3-SC.