Homogenous Bismuth LMCT Photocatalysis

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.