Dawn of photoredox catalysis

Photoredox catalysis, which facilitates organic transformations under visible-light irradiation, including sunlight, has garnered considerable attention as a cornerstone of green chemistry. Since the early days of this field around 2010, the author's group has made substantial contributions to its advancement. This review article provides a concise overview of the history and fundamental principles of photoredox catalysis, along with highlights of the achievements by the author's group. Although colorless organic compounds cannot be directly activated by visible light, photo-excited colored catalysts, with their two half-occupied frontier orbitals, play dual roles via electron transfer processes with organic substrates. The hole in the lower-energy orbital functions as a single-electron oxidant, whereas the electron in the higher-energy orbital acts as a single-electron reductant, enabling the formation of reactive radical intermediates from diverse organic compounds, including colorless ones. The discussion will focus on the key transformations developed by the author's group, including bimetallic photocatalysis, fluoroalkylation, and catalysis in aqueous media.