Visible‐Light‐Induced Homolysis of Earth‐Abundant Metal‐Substrate Complexes: A Complementary Activation Strategy in Photoredox Catalysis

The mainstream applications of visible‐light photoredox catalysis predominately involve outer‐sphere single‐electron transfer (SET) or energy transfer (EnT) processes of precious metal RuII or IrIII complexes or of organic dyes with low photostability. Earth‐abundant metal‐based MnLn‐type (M=metal, Ln=polydentate ligands) complexes are rapidly evolving as alternative photocatalysts as they offer not only economic and ecological advantages but also access to the complementary inner‐sphere mechanistic modes, thereby transcending their inherent limitations of ultrashort excited‐state lifetimes for use as effective photocatalysts. The generic process, termed visible‐light‐induced homolysis (VLIH), entails the formation of suitable light‐absorbing ligated metal–substrate complexes (MnLn‐Z; Z=substrate) that can undergo homolytic cleavage to generate Mn−1Ln and Z. for further transformations. The use of earth‐abundant metal complexes in photoredox catalysis offers a complementary mode of activation for organic substrates through visible‐light‐induced homolysis (VLIH) of metal–substrate bonds. This Minireview describes different electronic transitions that occur in photoexcited metal–substrate complexes as well as recent advancements and future prospects in this area.