Organic Photoredox Catalysts Exhibiting Long Excited-State Lifetimes

Organic photoredox catalysts with a long excited-state lifetime have emerged as promising alternatives to transition-metal-complex photocatalysts. This paper explains the effectiveness of using long-lifetime photoredox catalysts for organic transformations, focusing on the structures and photophysics that enable long excited-state lifetimes. The electrochemical potentials of the reported organic, long-lifetime photocatalysts are compiled and compared with those of the representative Ir(III)- and Ru(II)-based catalysts. This paper closes by providing recent demonstrations of the synthetic utility of the organic catalysts. 1 Introduction 2 Molecular Structure and Photophysics 3 Photoredox Catalysis Performance 4 Catalysis Mediated by Long-Lifetime Organic Photocatalysts 4.1 Photoredox Catalytic Generation of a Radical Species and its Addition to Alkenes 4.2 Photoredox Catalytic Generation of a Radical Species and its Addition to Arenes 4.3 Photoredox Catalytic Generation of a Radical Species and its Addition to Imines 4.4 Photoredox Catalytic Generation of a Radical Species and its Addition to Substrates Having C equivalent to X Bonds (X=C, N) 4.5 Photoredox Catalytic Generation of a Radical Species and its Bond Formation with Transition Metals 4.6 Miscellaneous Reactions of Radical Species Generated by Photoredox Catalysis 5 Conclusions