The Mechanism of Photosensitised Reactions in Solution

Photosensitised reactions in solution generally prooeed by mechanisms involving free radicals and radical ions. The initial step in all these processes is the interaction between an electronically excited form of the light–absorbing molecule and a suitable acceptor molecule which must be present in the system. A number of different examples have been discussed, particularly those where (i) the initial processes are identioal with the elementary process of the quenching of the fluorescence of the light–absorbing molecule and where (ii) the light–absorbing molecule undergoes transition to a triplet state (G. N. Lewis) which is capable of initiating the photosensitised reaction.