Prof. Andy Borovik
Title: Biological C–H Bond Activation
Bio:
A. S. Borovik was raised in Chicago and received his B.S. degree in Chemistry with Honors from Humboldt State University. As an undergraduate student he did research at Oregon State University as an NSF Summer Fellow and at Woods Hole Oceanographic Institution as a WHOI Fellow. Both research experiences involved using nuclear chemistry to trace metal ions in the environment. He obtained his Ph.D. in Chemistry at the University of North Carolina-Chapel Hill under Tom Sorrell where he developed photophysical models for the active site of copper proteins. As an NIH postdoctoral fellow with Larry Que at the University of Minnesota, he designed synthetic complexes that replicated the properties of dinuclear iron centers in proteins. Upon completion of his postdoctoral fellowship, Professor Borovik joined the faculty at Ithaca College where he taught chemistry and mentored 6 undergraduate research students for two years. He then moved to the University of California-Berkeley as a postdoctoral associate with Ken Raymond, working on stereonostic coordination chemistry. From there, he joined the Chemistry Department at Kansas State University where he began a broad program on the effects of the secondary coordination sphere on metal ions. After 3 years, he moved his research group to the University of Kansas, continuing research on the development of metal complexes and hybrid porous solids with unique structural and functional properties. In 2006, Professor Borovik and his research group moved to the University of California-Irvine, expanding his approach to include designing artificial metalloproteins. Professor Borovik has won several teaching and research awards that include a 2017 MERIT Award from the NIH, the 2018 National Cotton Award in Synthetic Inorganic Chemistry from the American Chemical Society, and the 2019 Tolman Award from the Southern California Section of the American Chemical Society. He is currently a UCI Distinguished Professor and was the 2022 Chair of the Division of Inorganic Chemistry of the American Chemical Society.
Abstract:
The oxidation of substrates via the cleavage of thermodynamically strong C–H bonds is an essential part of mammalian metabolism. These reactions are predominantly carried out by enzymes that produce high valent metal–oxido species, which are directly responsible for cleaving the C–H bonds. While much is known about the identity of these transient intermediates, the mechanistic factors that enable metal–oxido species to accomplish such difficult transformations are still incomplete. For synthetic metal–oxido species, C–H bond cleavage is often mechanistically described as synchronous proton coupled electron transfer (PCET). However, data have emerged that suggest the basicity of the M– oxido unit is the key determinant in achieving enzymatic function, thus requiring alternative mechanisms whereby proton transfer (PT) has a more dominate role than electron transfer (ET). This presentation will describe our research to gain mechanistic insights into how metal–oxido complexes activate C–H bonds. We have used a series of well-characterized Mn(III)– and M(IV)–oxido complexes to show that PT has a dominate role in the activation processes. Our experimental findings led to a proposed PCET mechanism with asynchronous transition states that is dominated by PT. To support this premise, a new semi-empirical free energy analysis was developed that can predict the relative contributions of PT and ET for a given set of substrates. These findings underscore why the basicity of M–oxido units needs to be considered in C–H functionalization.
Keywords: C-H Bond Acidities, Metal-Oxido Species, Proton-Couple Electron Transfer, Imbalanced Transition States
Faculty Host: Prof. Thomas Brunold