Photoreduction of thioxanthen-9-one and benzophenone by amines. Electrical conductivity and light emission studies

Abstract

The reactions of thioxanthen-9-one (TX) triplets with various amines (1,4-diazabicyclo[2,2,2]octane, DABCO, diphenylamine, DPA, triethylamine, TEA, triisobutylamine, TIBA and aniline, AN), in acetonitrile solution at room temperature have been investigated, and in some cases compared with the reactions of benzophenone (BP) triplets. In all cases the formation of free ions has been evidenced by photocurrent measurements. Apart from the system TX–DABCO free ions are formed in a complex process (involving more than one elementary reaction) which implies that the quantum yield Φ(ion) cannot be simply related to the oxidation potential of the amines. In the system TX–DABCO and BP–DABCO the same rate constant (1.2 × 10¹⁰ dm³ mol^–1 s^–1) has been found for the formation of free ions and the decay of triplets (determined by luminescence measurements).