Biological systems couple electrons and protons and employ electron and proton tunneling for energy conversion processes.  This talk will focus on how motifs from biology may be used to derive principles for guiding catalyst design.  A general theory of proton-coupled electron transfer (PCET) that includes 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, has been developed.  This formulation enables the calculation of rate constants and kinetic isotope effects for comparison to experiment.  Applications to PCET reactions in enzymes and electrochemical systems will be presented.  Studies of the enzyme soybean lipoxygenase provide a physical explanation for the experimental observation of unusually high kinetic isotope effects for C-H bond activation at room temperature.  Investigations of biologically inspired molecular electrocatalysts for hydrogen production identify the thermodynamically and kinetically favorable mechanisms and guide the theoretical design of more effective molecular electrocatalysts.  These molecular electrocatalysts include cobaloximes, hangman metalloporphyrins, and bioinspired models for hydrogenase enzymes.  A recent combined experimental and theoretical study of a series of substituted benzimidazole-phenol model systems inspired by the Tyr<sub>Z</sub>-His190 redox proton relay found in photosystem II will also be discussed.  Application of the PCET theory to these systems has provided mechanistic insights into the PCET processes occurring in these types of proton relay systems. The calculated reduction potentials and kinetic isotope effects are in agreement with the experimental values and provide an explanation for the differences among the model systems. The mechanistic insights are guiding the design of artificial photosynthetic systems capable of PCET processes involving proton translocation via multiple proton transfers.<br/>

Inspiration from biology: Coupling electrons and protons and facilitating tunneling

254th National Meeting (2017)

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