2020 Theses Doctoral

Harnessing Photophysical Processes to Improve Photoredox Catalysis

Ravetz, Benjamin

Photoredox catalysis has revolutionized organic chemistry, and beyond, over the past 10 years. As a field, we’ve explored the scope of this methodology in synthesis, materials chemistry, and photoenzymatic catalysis. Even with these impressive advances in reactivity, photocatalysts carry flaws within their photophysics which remain largely unaddressed. We target specific photophysical processes to improve scalability, selectivity, and robustness in synthetic photoredox catalysis. Additionally, leveraging unique photophysical transitions uncovers hidden reactivity in organic synthesis. We begin by using photoredox catalyst as mild reductant of Co(II) for [2+2+2] cycloadditions to make benzenes and pyridines. Then, we apply this methodology to a temporally controlled polymerization. During these studies, we uncover ligand-to-metal charge transfer (LMCT) as a new mode of Co(II) activation. Later, we manipulate triplet fusion upconversion systems to address fundamental challenges in photoredox catalysis. Along that vein, we work towards using singlet fission to achieve multi-electron photoredox. Finally, we investigate the advantages of spin-forbidden excitations in scaling photoredox catalysis, achieving mole-scale photoredox.