Tetrametallic Copper Complex to Nanoscale Copper: Selective and Switchable Dehydrogenation-Hydrogenation under Light

A discrete, photoactive, ultrafine copper nanocluster of fewer than hundreds of atoms with stimuli-responsive switchable redox-active states is highly desired to control two different antagonistic reactions. Herein, a mixed-valent tetrametallic copper complex ( C-1 ) of N−O-N Schiff base ligand is disclosed, in which the five different Cu−Cu interactions were used to generate photoactive nanoscale copper [LCu⁰_n, S-1 ] through the reduction of coordinated imine to the amine of C-1 . The presence of a ligand provides stability and helps to homogenize the material ( S-1 ) in the organic solvent. The cluster showed stimuli (O₂/light)-responsive switching between its reduced ( S-1 ) and oxidized [LCu⁰_n−mCuO_m, S-2 ] states that allows it to serve as a highly and poorly active (bistate, relative rate >5–12 fold) catalyst for the dehydrogenation of alcohols to aldehydes and hydrogenation of nitroaromatics to amino aromatics under the light.