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-m CuOm , 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.