A theoretical study on the photoisomerization of thiophene

Abstract

The photoisomerization of thiophene (3–5 and 2–4 transpositions of carbon atoms) has been studied with ab initio SCF and CI calculations. A possible reaction mechanism from the lowest excited singlet state 1B2 of thiophene can be proposed from potential surface via Dewar thiophene. The 1B2 state of thiophene would easily convert to the biradical intermediate by almost one step. The internal conversion of this species to the S0 state would cause to the transposition of carbon atoms. The effect of phenyl substituent is also discussed.