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 O 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 O-THT and O-PyD, whereas four bands are observed for O-TAD, which contains both N and S atoms in the heterocyclic ring. Upon visible-light irradiation, O-THT and O-PyD form their corresponding oxide derivatives, tetrahydrothiophene-1-oxide and pyrrolidine--oxide. Although two O-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--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(P) and the paired ring molecule.