Deoxygenation of dibenzothiophene-S-oxide and dibenzoselenophene-Se-oxide: A comparison of direct and sensitized photolysis

Photolysis of dibenzothiophene-S-oxide (DBTO) and dibenzoselenophene-Se-oxide (DBSeO) was examined under direct and sensitized conditions. Quantum yield and solvent oxidation data are used to separate the direct irradiation conditions, plus benzophenone-sensitized and anthraquinone-sensitized irradiation of DBSeO, into one mechanistic class. Acridine-sensitized photolysis of DBSeO and triplet sensizitization of DBTO result in deoxygenation, but go by different mechanisms than the direct irradations. The two sensitized cases that appear mechanistically linked to direct photolysis are ones in which the spectroscopic triplet of DBSeO, which is very likely of comparable energy to the SeO BDE, is populated by triplet energy transfer.