Photochemical reactions of substituted cyclopropenium salts

Photochemical reactions of triphenylcyclopropenium tetrakis(pentafluorophen yl)gallate (TPCPGa) and diphenyl-(2-methoxy-1-naphthyl)-cyclopropenium tetr akis(pentafluorophenyl)gallate (DPMNCPGa) (Chart 1) have been investigated in acetonitrile. Traces of water were required for the photochemical reacti ons to proceed. The disappearance of both TPCPGa and DPMNCPGa obeys zero-or der kinetics with rate constants (k) having a linear dependence on the conc entration of water. Electron-transfer from water to the cyclopropenium cati on is proposed as the primary process in the formation of the cyclopropenyl radical. The latter dimerizes leading to the photoproducts.