Moving electrons in electrocatalysts and through metalloproteins

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This inorganic chemistry research program is developing new approaches to design and rationalize proton-coupled electron transfer (PCET) reactivity in small molecule catalysts and in artificial biochemical systems. Our long-term goals are to use the fundamental chemistry from those systems to design the next generation of catalysts for challenging biological oxidations (e.g., bioremediation) and energy storage technology (e.g., carbon dioxide reduction). This program focuses on the factors that influence the two most fundamental chemical reactions: proton transfer and electron transfer. Such PCET reactions are crucial for function in diverse systems, including in chemical catalysis (e.g., the 2 electron reduction of CO2 to CO and H2O) and protein function (the PCET oxidation of tyrosine to tyrosyl radical). Great strides have been made in understanding the essential features of PCET in chemical and biochemical reactions, but new developments in technology have given rise to new questions. For biological redox systems, thinking has continued to evolve about how proteins use microenvironments to affect the rate and efficiency of electron transfer (ET). Long-term Objective 1 of this proposal addresses the local non-covalent interactions (i.e., microenvironment) that affect the redox properties of the aromatic residues tyrosine and tryptophan. Our work will probe these new questions using protein model systems built to test how local interactions modify the rates and energetics of ET and PCET chemistry of tyrosine. Long-term Objective 2 places emphasis on microenvironment effects in small molecules, where those local interactions also exert a profound influence on catalyst function and performance. For example, the concept of "proton relays" transformed the field of molecular PCET electrocatalysts. However, there remains a fundamental knowledge gap between those molecular electrocatalysts and catalytic materials that are viewed as scalable technologies. Consequently, our efforts in long-term Objective 2 will expand on emerging iron, cobalt, rhenium, and ruthenium catalyst design concepts by probing the local effects of acid/base chemistry and charged groups proximal to metal sites, specifically for CO2 and O2 reduction catalysts. Those ideas will be used to design and investigate heterogeneous catalyst scaffolds based on coordination complex nodes. Overall, the proposed research will generate a fundamental understanding of how the composition of local groups affects redox reactions of amino acids, protein metal sites, molecular electrocatalysts, and materials. In turn, those results will be used in the designs of future catalysts. My conceptually cross-cutting research program is a proving ground for the development of superior HQP with modern laboratory skills (including safety) and highly sought oral/written communications skills. The result is a research group that is a destination for diversity and world-class chemistry.