Photoreactions of Ozone–Tetrahydrothiophene, Ozone–Pyrrolidine, and Ozone–Thiazolidine Complexes Studied Using Matrix-Isolation IR and Visible Absorption Spectroscopies

The photoreactions of molecular complexes composed of O₃ and three 5-membered heterocyclic compounds, tetrahydrothiophene (THT), pyrrolidine (PyD), and thiazolidine (TAD), are systematically investigated using matrix-isolation infrared (IR) and UV–visible spectroscopies. Two visible-light absorption bands appear in the visible spectra obtained for O₃-THT and O₃-PyD, whereas four bands are observed for O₃-TAD, which contains both N and S atoms in the heterocyclic ring. Upon visible-light irradiation, O₃-THT and O₃-PyD form their corresponding oxide derivatives, tetrahydrothiophene-1-oxide and pyrrolidine-N-oxide. Although two O₃-TAD complexes with different photoreactivities are detected, both structures form thiazolidine-1-oxide upon combining with O and S atom in the heterocyclic ring, but not thiazolidine-N-oxide. The mechanism of formation of these oxide compounds can be explained by the stability of the oxide compound in the triplet state formed via the combination of O­(³P) and the paired ring molecule.