Photoactive four-coordinate copper(i) complexes based on chelating diimine, diphosphine, and diisocyanide ligands with high excited-state energies

Abstract

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.