A laser flash photolysis study of dibenzothiophene sulfoxide and benzo[b]naphtho[2,1-d]thiophene-11-oxide

The photodeoxygenation reaction of dibenzothiophene sulfoxide (1) and of benzo[b]naphtho[2,1-d]thiophene-11-oxide (3) have been studied by nanosecond laser flash photolysis. Laser irradiation of 1 using sensitization with benzophenone leads to formation of a transient with absorption at 380 nm and a lifetime of around 140 ns. Triplet sensitized steady state irradiation of 1 indicates that the triplet state is not responsible for the direct photodeoxygenation.Laser flash photolysis of 3 leads to the formation of a transient with a maximum absorption at 445 nm and a lifetime of around 3 μs. This transient was characterized as the triplet 3 by quenching with β-carotene. Quenching experiments indicate that the triplet energy is less than 56 kcal/mol.