A new copper(I)–triazenido electro-catalyst for catalyzing hydrogen evolution from acetic acid and water

• Reaction of a triazenido ligand (HL) and CuI gives a dinuclear triazenido complex {Cu2(L)2} 1.
• 1 can catalyze hydrogen evolution from acetic acid with TOF of 65 mol H2/mol catalysts/h.
• 1 can also catalyze hydrogen evolution from neutral buffer (pH 7.0) with TOF of 324 mol H2/mol catalysts/h.
• Sustained water reduction catalysis to give H2 over a 72 h electrolysis period with 97% Faradaic yield.

The reaction of 2-chloroaniline and o-anisidine afforded a new triazenido ligand, 1-[(2-methoxy) benzene]-3-[2-(chloro)benzene] triazene (HL). In the presence of Et3N, the reaction of HL and CuI gave a triazenide complex {Cu2(L)2} 1, a new molecular electrocatalyst, which has been determined by X-ray crystallography. The CuCu distance of 2.4764(8) Å is significantly shorter than the sum of the van der Waals radii of Cu (1.40 Å). Electrochemical studies indicated that the catalyst can catalyze hydrogen evolution from both acetic acid with a turnover frequency (TOF) of 65 (in DMF) moles of hydrogen per mole of catalyst per hour at an overpotential of 942 mV and neutral buffer (pH 7.0) with a TOF of 324 moles of hydrogen per mole of catalyst per hour at an overpotential of 939 mV vs SHE, respectively. Sustained proton reduction catalysis occurs at glassy carbon (GC) to give H2 over a 72 h electrolysis period with 97% Faradaic yield and no observable decomposition of the catalyst.

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