Project Summary Organic Photoredox Catalysts for Synthetic Method Development Garret M. Miyake, Colorado State University, Department of Chemistry Catalysis is arguably the most important chemical contribution to society as it enables the synthesis of medicines and materials that are critical to enhancing human lives. To address current and future health needs, the development of catalyst systems that accelerate the discovery and manufacturing of medicines through new and more efficient chemical reactions are necessary. However, many classic catalytic methodologies employ precious metals, hazardous reagents, or forcing conditions. By contrast, photoredox catalysis has emerged as a powerful approach to access unique reaction pathways and drive chemical reactions using light. Advantages of photoredox catalysis include the ability to perform reactions under mild conditions, obviation of hazardous and non-selective reagents, achievement of new selectivity, increased functional group tolerance, increased reaction efficiencies, and access to unprecedented reaction intermediates and manifolds. Much of the work in photoredox catalysis has applied well- studied precious metal complexes or organic dyes that possess oxidizing excited states as the catalysts. As such, to address metal contamination, sustainability, and the need for expanded and novel reactivity, new organic photoredox catalysts with diverse photophysical and electrochemical properties must be developed. The long-term goal of the proposed research activities is to develop organic photoredox catalyst systems that enable novel and improved syntheses of small molecules and materials that address human health needs. This proposal describes the development of organic photoredox catalyst systems with unprecedented redox potentials that enable new chemical reactivity. We will employ a combination of experimental and computational approaches to gain a fundamental understanding into the catalysts and reaction mechanisms. Through mechanistically guided catalyst design, we seek to engineer systems that can access the extremely reducing or oxidizing chemical potentials necessary to enable challenging reactivity. Ultimately, this research will contribute to human health through the development of catalysts with unique reactivity to enable new and improved syntheses of medicines and medically important materials.