2015 Mary E. Kapp Lecture

Dr. James M. Mayer
Yale University

“Proton-Coupled Electron Transfer: from Hydrogen Atom Transfer Reactions to Oxide Nanoparticle Chemistry”

Research in the Mayer group spans the fields of inorganic, materials, bioinorganic, organometallic, and physical organic chemistry. Our primary focus is on redox reactions that involve bond formation and bond cleavage, in particular the coupled transfers of protons and electrons. Proton/electron transfers are central to a variety of important processes, from fuel cells and solar fuels to bioenergetics, from organic free radical reactions and reactive oxygen species to enzymatic oxidations, and from the properties of nanoscale metal oxides to interfacial charge transfer.

One aspect of our work is developing fundamental descriptions of the different classes of proton-coupled electron transfer (PCET) reactions. We have shown, for instance, that hydrogen atom transfers are typically well described by a model based on Marcus Theory. Studies of photo-induced PCET in phenol derivatives are probing reactions near the barrierless limit. Transition metal complexes are being synthesized with separated redox and acid/base sites, to probe the effect of separating the H+ and e–,as models for biological PCET processes. PCET principles are being applied to the development and study of electrocatalysts for small molecule transformations, such as O2 + 4H+ + 4e– Û 2H2O, which is key to fuel cell and solar fuel technologies. The Mayer group has recently shown that PCET is also a key concept in materials chemistry and interfacial charge transfer reactions. For instance metal oxide nanocrystals can transfer H+ and e– to organic reagents. The Figure below illustrates the similarity of this process with molecular separated PCET reactions.

PFe_ZnOH