Proton-Coupled Electron Transfer in Photoredox Catalytic Reactions

Abstract

Proton-coupled electron transfer (PCET) is studied in different research domains of chemistry. Many reports involve biochemical processes. Although related phenomena have often been investigated in photochemical electron- and hydrogen-transfer processes, only recently have a larger variety of such steps come to be discussed under the comprehensive concept of PCET. In photoredox catalytic reactions applied to organic synthesis, various PCET steps have been identified in cases in which redox or simple electron-transfer steps are estimated to be endergonic by simple comparison of redox potentials. Such steps become exergonic when the electron transfer is coupled with proton transfer. In this article, examples of photoredox catalytic reactions of synthetic interest are reported, with the PCET discussed in detail.