CAS: Next Generation Photocatalysts for Main Group Bond Formation

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Rory Waterman of the University of Vermont will study more efficient ways to form chemical bonds using metal compounds that are activated by light, a process called photocatalysis. The goal of this project is to investigate a new phenomenon in photocatalysis discovered in Prof. Waterman’s group, wherein the bonds to the metal photocatalyst are altered when exposed to light. Through a deeper understanding of this process, more efficient approaches to value-added products in the agrichemical, health, and consumer goods sectors will be developed. Specifically, photocatalytic approaches to forming bonds between the carbon and elements such as phosphorus, nitrogen, and sulfur, will be studied. By using photocatalysts, these compounds can be obtained with less waste and increased energy efficiency. Because the methodologies in the study are straightforward and many target metals are low or non-toxic, this project is an excellent way to include local high school students from underserved populations in Vermont as well as providing training for undergraduate and graduate students. The explosive popularity of photocatalysis has been driven by catalysts featuring rarified metals that engage in redox or radical reactions. In this study, the photocatalysts are excited in a charge transfer process that does not result in redox reactions and instead accelerates closed-shell, or non-radical, reactivity. Through spectroscopic analysis and computational modeling of known catalysts, the common features that determine activity and predictive power in discovering new catalysts can be uncovered. The starting hypothesis is that this photocatalysis involves bond-elongation in the excited state, and exploration of the mechanism will afford a greater understanding of what appears to be a general photochemical phenomenon among compounds with a metal-element bond in which the element has a lone pair of electrons. In the process of catalyst discovery, candidate catalysts using metals that are more sustainable and less toxic will be targeted for testing and study. Furthermore, efforts to extend this catalysis from preliminary examples of these reactions to the broadest set of substrates will be undertaken. These aims of greater understanding, discovery of new catalysts, and exploration of new reactivities will be used to prepare targets of known value to a range of sectors. This focus will provide participating students and trainees support in their assuming roles in the 21st century chemical/STEM workforce. 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.