Tuning Co‐operative Energy Transfer in Copper(I) Complexes Using Two‐Photon Absorbing Diimine‐Based Ligand Sensitizers

Photocatalysis mediated by low energy light wavelengths has potential to enable safer, sustainable synthetic methods. A phenanthroline‐derived ligand bathocupSani, with a large two‐photon absorption (TPA) cross section was used to construct a heteroleptic complex [Cu(bathocupSani)(DPEPhos)]BF4 and a homoleptic complex [Cu(bathocupSani)2]BF4. The ligand and the respective homoleptic complex with copper exhibit two‐photon upconversion with an anti‐Stokes shift of 1.2 eV using red light. The complex [Cu(bathocupSani)2]BF4 promoted energy transfer photocatalysis enabling oxidative dimerization of benzylic amines, sulfide oxidation, phosphine oxidation, boronic acid oxidation and atom‐transfer radical addition.