CAREER:CAS: Mechanistic Investigation of Photoredox Reactions

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In this CAREER project, funded by the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, John Swierk of the Department of Chemistry at Binghamton University (SUNY) is investigating the kinetics and mechanisms of photoredox reactions. These reactions utilize light to generate new and difficult-to-access chemical bonds that are relevant in the synthesis of pharmaceuticals and other small molecules. The goal of this research is to provide a solid mechanistic foundation for photoredox reactions that are successful but poorly understood. Results from this project have the potential to lead to faster reaction rates and product yields, as well as enable the development of new reactions. This work lies at the interface of organic, physical, and inorganic chemistry and will support the interdisciplinary training of scientists at all levels. Community college students will be integrated into the research program as trainees as part of broader outreach activities focused on facilitating successful transitions of STEM (science, technology, engineering and mathematics) students from two-year to four-year universities. Photoredox reactions rely on the generation and control of short-lived radical intermediates. While successful, the underlying reaction steps and kinetics of photoredox reactions are poorly characterized. The proposed work seeks to identify the key kinetic descriptors at a molecular level that control selectivity via different pathways (e.g., persistent radical effect, radical chain mechanism). These molecular level insights are then to be connected with information about reaction outcomes, such as product yield and quantum efficiency. In addition, the proposed work also seeks to understand how ionic media can be used to tune the rate of unproductive electron transfer pathways. Studies of photoredox reactions in deep eutectic solvents (DES) represent a new direction for both fields and the information gleaned from these studies may allow for the development of functional, rationally designed solvents that can enhance product selectivity and reaction rates. Fundamental investigations into electron and hydrogen atom transfer in DES are important with the goal of supporting the development of new photoredox methods. More broadly, investigations into the stability of long-lived radicals, H-atom transfer catalysts, radical chain mechanisms, and electron transfer have the potential to expand the impact of this proposed work beyond photoredox catalysis.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.