Unimolecular cooperative metallaphotocatalysis with conjugately bridged Ir–Ni complexes and its applications in organic coupling reactions

Abstract

Recent advances successfully upgraded the unique cooperative partnership between two distinct metals in photocatalysis. Herein we report the design, synthesis and comprehensive study of a series of heteroleptic Ir(III) complexes with a pendant binding site for nickel. The neutral Ir·L^pytz complexes are apt to generate a novel unimolecular Ir–Ni bimetallic system in situ during photocatalytic organic transformations where the pyridyl triazole ligand (L^pytz) acts as the conjugated bridge between Ir and Ni metal centers. A comparative study revealed that the bimetallic unimolecular system with a conjugated linker is a convenient alternative to a bimolecular system. UV-visible and photoluminescence quenching studies showed the importance of the conjugated bridging ligand to vectorial transfer of electrons from the photosensitizer unit to the reaction site. All novel Ir·L^pytz complexes were evaluated in three challenging, mechanistically distinct photoinduced cross-coupling reactions (C–O, C–S and C–N) to demonstrate the enormous potential of a conjugately bridged Ir–Ni catalytic system, thus representing an alternative unimolecular bimetallic strategy for photocatalytic Ni mediated cross-coupling reactions.