Photolysis of the ion pair triphenylsulfonium thiophenolate induced by outersphere charge transfer excitation

The ion pair Ph3S+PhS− can be viewed as a sulfur-based mixed-valence system which is characterized by a PhS− to Ph3S+ outersphere charge transfer (OSCT) absorption at λmax=390 nm (in CHCl3). OSCT excitation leads to the radical pair Ph3S/PhS which undergoes subsequent elimination and radical coupling processes with the final formation of Ph2S. The photolysis proceeds with a quantum yield of φ=0.23 at λirr=436 nm.