Ligand-to-metal charge transfer (LMCT) photocatalysis allows the activation and synthetic utilization of halides and other heteroatoms in metal complexes. Many metals are known to undergo LMCT but so far remain underutilized in the field of catalysis. A screening assay identifying LMCT activity helped us to expand this catalysis concept to the application of bismuth LMCT in organic radical coupling reactions. We demonstrate its application for the generation of two different radicals (chlorine and carboxyl) in net-oxidative as well as redox-neutral photochemical reactions. Detailed investigation of the model Giese-type coupling revealed BiCl4 – and BiCl5 2– as catalytically active bismuth species under 385 nm irradiation. Combined cyclic voltammetry and UV–vis studies gave insight into the reactivity of the highly reactive bismuth(II) catalyst fragment.

Ligand-to-metal charge transfer (LMCT) photocatalysis allows the activation and synthetic utilization of halides and other heteroatoms in metal complexes. The coordination makes photoinduced intramolecular electron transfer processes even at very short excited state lifetimes possible. A screening assay identifying LMCT activity enabled us to expand this catalysis concept to main group elements, such as bismuth. Bismuth (III) complexes generate the elusive bismuth (II) species and electrophilic carboxyl and chlorine radicals upon irradiation. The latter was utilized in C(sp3)–H bond activation and redox neutral trapping in a Giese-type coupling protocol. Combined cyclovoltammetry and UV-vis studies gave insight in the radical behavior of the highly reactive bismuth (II) catalyst fragment.