CAS: Forming Transition Metal Hydride Complexes via Excited-State Proton-Coupled Electron Transfer

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In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Jillian Dempsey of the Department of Chemistry at University of North Carolina (UNC) is studying pathways by which light capture and proton/electron reactivity can be directly integrated in coordination complexes. The goal of this research is to establish new photon-driven pathways for the formation of transition metal hydride complexes. Transition metal hydride complexes are key intermediates in many catalytic processes that drive the formation of fuels and commodity chemicals and thus developing approaches to promote their formation with solar photons will help improve sustainability in energy intensive catalytic reactions. The proposed research activities will help develop a globally competitive STEM workforce by providing students with training in synthesis, electrochemistry, spectroscopy, and effective science communication. Complementary activities will take a multi-faceted approach to increase diversity in science and enhance training of scientists. Interactive table-top activities deployed at the UNC Science Expo and local schools will introduce K–12 students to the science of renewable energy. Professor Dempsey co-leads the Chemistry Women Mentorship Network, which matches graduate student and postdoc women interested in academic careers with extramural faculty mentors and provides resources needed to support successful mentoring relationships. The development of coordination complexes capable of undergoing proton-coupled electron transfer in their excited states promises to reveal new photon-driven pathways to metal hydride complexes. However, little is fundamentally known about how to directly integrate light capture and proton electron reactivity in coordination complexes, especially to yield transition metal hydride complexes. This work will carry out systematic studies to address this gap in knowledge and subsequently to apply an enhanced understanding to establish unprecedented excited-state reactivity of coordination complexes. Specifically, this research will 1) Provide a deeper understanding of excited-state electronic structures that support proton-coupled electron transfer reactions and 2) Demonstrate that coordination complexes can undergo a proton-coupled electron transfer reaction in their electronic excited state to form a metal hydride complex. Ultimately, demonstration that metal hydride complexes can be formed via excited-state proton-coupled electron transfer will establish a new paradigm for light-driven fuel and chemical production.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.