Photoactive four-coordinate copper(I) complexes based on chelating diimine, diphosphine, and diisocyanide ligands...

Tetrahedral complexes of copper(I), a more abundant metal than the precious metals traditionally used, have emerged as a suitable alternative in photochemistry and photophysics. While many ligand designs focus on chelating α-diimine and diphosphine ligands, here we report the effect of chelating diisocyanide ligands on photoactive copper(I) complexes. Three new heteroleptic copper(I) complexes are exhibiting photoluminescence at room temperature from a ³MLCT excited state, and a homoleptic isocyanide copper(I) complex luminesces from a ligand-centered state. Among the three new heteroleptic complexes, the one that combines a diphosphine and diisocyanide ligand led to a nearly ideal tetrahedral geometry and an unusually high ³MLCT excited-state energy. This high triplet energy was used in a proof-of-principle upconversion process and triplet-triplet energy transfer photocatalysis. Our findings demonstrate how diisocyanide chelate ligands can be used to tune the photophysical and photochemical properties of photoactive copper(I) complexes with four-coordinate coordination environments.