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 [LCu0n, 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 [LCu0n−mCuOm, 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. [ABSTRACT FROM AUTHOR]