Reduction of aryl halides by consecutive visible light-induced electron transfer processes

Abstract

Biological photosynthesis uses the energy of several visible light photons for thechallenging oxidation of water, whereas chemical photocatalysis typically involves onlysingle-photon excitation. Perylene bisimide is reduced by visible light photoinducedelectron transfer (PET) to its stable and colored radical anion. We report here thatsubsequent excitation of the radical anion accumulates sufficient energy for the reductionof stable aryl chlorides giving aryl radicals, which were trapped by hydrogen atom donorsor used in carbon-carbon bond formation. This consecutive PET (conPET) overcomes thecurrent energetic limitation of visible light photoredox catalysis and allows thephotocatalytic conversion of less reactive chemical bonds in organic synthesis