Rotational photoisomerization mechanism of a thioamide, N-5-trifluoromethyl-6-methoxy-1-thionaphthoyl-N-methylglycine

Abstract

A thioamide, N-5-trifluoromethyl-6-methoxy-1-thionaphthoyl-N-methylglycine, undergoes trans $\leftrightharpoons$ cis photoisomerization around C-N bond in solution. Azulene quenching experiments showed that the photoisomerization proceeds via both singlet and triplet excited states. The total quantium yield of the trans cis photoisomerization is about 0.26, 0.14 from pure singlet excited state and 0.12 from pure triplet excited state. Intersystem crossing and internal conversion quantum yields were calculated from sensitized photostationary state experiments and a plausible mechanism is proposed which is supported by external heavy atom effect.