Homoleptic copper( <scp>i</scp> )–bisphosphine complexes as photoredox catalysts

Copper photoredox catalysis has emerged as a practical methodology in organic synthesis, with tetracoordinate copper complexes playing a central role. Among these, homoleptic complexes bearing two bisimine ligands (CuN4) and heteroleptic complexes containing one bisimine and one bisphosphine ligand (CuN2P2) are the most utilized. In contrast, homoleptic copper-bisphosphine complexes (CuP4) have received comparatively less attention, despite their recent involvement in novel synthetic transformations. Herein, we report a systematic study of this underexplored family of copper complexes. Representative CuP4 complexes were synthesized, and their photophysical and electrochemical properties were characterized. Their photocatalytic activity was demonstrated in representative coupling reactions. The results provide insights for guiding future ligand design to develop more active copper-based photocatalysts.