With this CAREER Award, the Chemical Structure, Dynamic and Mechanism B program is supporting the research of Professor Jillian L. Dempsey at the University of North Carolina. Professor Dempsey is studying mechanisms of excited-state proton-coupled electron transfer (PCET) reactions in a series of model systems. This work will reveal how light absorption and proton/electron transfer can be integrated and will help identify new approaches to drive energy-intensive PCET reactions directly with sunlight. New synthetic and spectroscopic approaches enable the study of PCET reactions in which both the proton transfer and electron transfer reactions can be monitored optically. In the proposed model systems, optical detection of reaction intermediates, kinetics modeling, thermochemical calculations and H/D kinetic isotope effects will all provide insight to the pathways by which light absorption is coupled to proton and electron transfer. Systematic investigations examining parameters such as driving force, electron transfer distance and proton transfer distance will help develop a fundamental understanding of PCET reactions involving reagents in electronically excited states. The model systems will incorporate biologically relevant substrates as well as complexes that were selected to reveal new mechanistic pathways by which small, inert molecules can be activated through PCET processes with excited-state reagents. Collectively, these investigations will provide an improved understanding of this little-explored class of reactions.
Professor Dempsey will also initiate a three-tier approach aimed at promoting diversity in science and ensuring future generations of well-trained scientists. First, new energy-based interactive demos will be developed. These activities, which are being utilized at the Morehead Planetarium and Science Center and a local elementary school, are introducing K-12 students-many of whom are from underrepresented groups-to the field of solar energy conversion and attracting them to STEM careers. Second, evidence-based teaching methods are being incorporated to a large chemistry course in order to improve student learning and retention. Third, the Chemistry Women Mentorship Network (ChemWMN) has been established and will help support women pursuing academic careers. In addition to the educational impacts, this work will increase knowledge of excited-state PCET processes, a class of reactions for which there have been few systematic experimental investigations, and reveal new photo-induced pathways to activate small molecules. By revealing pathways by which energy-intensive PCET reactions can be initiated by molecules in their electronic excited states, new approaches to efficiently convert solar photons into chemical energy, addressing solar energy storage challenges may ultimately be developed.
