Air-Stable Nickel(0) Complexes with Room-Temperature Photoluminescence

Building on the isoelectronic analogy between nickel(0) and copper(I), we develop photoactive nickel(0) complexes that, for the first time, approach the photophysical performance of their copper(I) counterparts.

By creating a coordination sphere that stabilizes the zero-valent oxidation state through strong π-backbonding and shielding it from the chemical environment, we obtain two nickel(0) complexes that are inert towards oxidation by air and show luminescence from a metal-to-ligand charge-transfer (MLCT) excited state with a quantum yield of near 0.03% and a lifetime of approximately 4 ns in solution at room temperature. The more electron-rich nature of nickel(0) compared to copper(I), as well as the unique role of nickel in modern cross-coupling catalysis, open perspectives for new inner-sphere photocatalysis beyond conventional photoredox strategies relying on simple molecular collisions, in addition to luminescence-based applications.