Proton‐Coupled Electron Transfers

The coupling between electron and proton transfers has a long experimental and theoretical history in chemistry and biochemistry. Proton-coupled electron transfer (PCET) reactions play a critical role in a wide range of biological processes, including enzyme reactions, photosynthesis, and respiration. This chapter details the mechanism analysis of PCET reactions that mainly consists in establishing whether proton transfer and electron transfers are concerted or stepwise as well as describing the kinetic characteristics of the concerted proton and electron transfer (CPET) reactions. It illustrates the intrinsic parameters of concerted pathways by experimental examples. The chapter ends with a discussion on the association between PCET and heavy-atoms electron-transfer/bond-breaking (forming) reaction, highlighting reaction pathways in which electron transfer, proton transfer, and bond-breaking (forming) are all concerted. Associating proton transfer to electron transfer might be additionally profitable to break bonds because of the thermodynamic advantage of concerted pathways over stepwise pathways.