Proton-coupled electron transfer (PCET) reactions play a vital role in a wide range of chemical and biological processes. Recent advances in the theory of PCET and key applications will be presented. The quantum mechanical effects of the active electrons and transferring proton, as well as the motions of the proton donor-acceptor mode and solvent or protein environment, are included in a general theoretical formulation. This formulation enables the calculation of rate constants and kinetic isotope effects for comparison to experiment. The application of this theory to artificial photosynthetic systems provides insight into the physical principles underlying proton relays, which play a critical role in photosystem II. Theory predicts a concerted two-proton transfer process associated with the electrochemical oxidation of certain substituted benzimidazole-phenols, accompanied by a decrease in the redox potential and a small kinetic isotope effect. Electrochemical, spectroelectrochemical, and kinetic isotope effect experiments subsequently validated these predictions. Calculations on photoreduced zinc oxide nanocrystals have elucidated the effects of proton diffusion between sites within the nanocrystals as well as the nature of PCET to the nitroxyl radical TEMPO. In addition, the development of theoretical approaches for simulating the ultrafast dynamics of photoinduced PCET will be discussed. These approaches have been applied to blue light-using flavin adenine dinucleotide (BLUF) photoreceptor proteins, which exhibit photoinduced PCET as part of the mechanism for light regulation of physiologically important processes. The calculations elucidate the mechanism of photoinduced PCET and its impact on local protein conformational changes that transmit important signals to distal regions of the protein. All of these applications illustrate the diversity and significance of PCET in catalysis and energy conversion processes.<br/>

Proton-coupled electron transfer in catalysis and energy conversion

255th National Meeting (2018)

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