Synthesis, Characterization, and Electrocatalytic Behavior for Hydrogen Evolution of a Dinuclear Copper(II) Complex of 1‐[(2‐Carboxymethyl) benzene]‐3‐[2‐carboxybenzene] triazene

A dinuclear copper(II) complex, [Cu II 2 (L) 2 ] is afforded by the reaction of CuCl 2 · 2H 2 O with a triazenido ligand, 1‐[(2‐carboxymethyl) benzene]‐3‐[2‐carboxybenzene] triazene (H 2 L). Structural investigation shows that the copper‐copper distance [2.3985(7) Å] is significantly shorter than the sum of the van der Waals radii of Cu (1.40 Å), suggesting that there are metal‐metal bonds in [Cu II 2 (L) 2 ]. In solid, there is a strong antiferromagnetic interaction between copper(II) ions ( J = –135.6 cm –1 ). In homogeneous environment, [Cu II 2 (L) 2 ] shows electrocatalytic activities for hydrogen generation both from acetic acid with a turnover frequency (TOF) of 32 mol of hydrogen per mole of catalyst per hour [mol(H 2 ) · mol –1 (catalyst) · h –1 ] at an overpotential (OP) of 941.6 mV, and neutral buffer with a TOF of 512 mol(H 2 ) · mol –1 (catalyst) · h –1 at an OP of 836.7 mV.