Highly Functional Dinuclear Cu-I-Complex Photosensitizers for Photocatalytic CO2 Reduction

Two dinuclear Cu-I complexes with two tetradentate ligands consisting of a diimine unit and two diphenylphosphine units connected with -C4H8- chains were synthesized. The Cu-I dimer with p-CF3 substituents worked as an outstanding redox photosensitizer for photocatalytic CO2 reduction; Fe-II(dmp)(2)(NCS)(2) (dmp = 2,9-dimethyl-1,10-phenanthroline) was used as a catalyst, and CO was produced with a quantum yield of 14.1%. This is one of the most efficient photocatalytic systems using only abundant elements. This Cu dimer was significantly durable: approximately 80% remained in the reaction solution after irradiation for 48 h, while the turnover number was TONCO = 778 based on the dinuclear CuI complex used.