Haddad Andrew Z, Cronin Steve P, Mashuta Mark S, Buchanan Robert M, Grapperhaus Craig A
Department of Chemistry, University of Louisville , 2320 South Brook Street, Louisville, Kentucky 40292, United States.
Inorg Chem. 2017 Sep 18;56(18):11254-11265. doi: 10.1021/acs.inorgchem.7b01608. Epub 2017 Aug 31.
In this study, we report the electrocatalytic behavior of the neutral, monomeric Cu(II) complex of diacetyl-bis(N-4-methyl-3-thiosemicarbazonato), CuL, for metal-assisted ligand-centered hydrogen evolution in acetonitrile and dimethylformamide. CuL displays a maximum turnover frequency (TOF) of 10 000 s in acetonitrile and 5100 s in dimethylformamide at an overpotential of 0.80 and 0.76 V, respectively. The rate law is first-order in catalyst and second-order in proton concentration. Gas analysis from controlled potential electrolysis confirms CuL as an electrocatalyst to produce H with a minimum Faradaic efficiency of 81% and turnover numbers as high as 73 while showing no sign of degradation over 23 h. The H evolution reaction (HER) was probed using deuterated acid, demonstrating a kinetic isotope effect of 7.54. A proton inventory study suggests one proton is involved in the rate-determining step. Catalytic intermediates were identified using H NMR, X-ray photoelectron, and UV-visible spectroscopies. All catalytic intermediates in the proposed mechanism were successfully optimized using density functional theory calculations with the B3LYP functional and the 6-311g(d,p) basis set and support the proposed mechanism.
在本研究中，我们报道了二乙酰 - 双（N - 4 - 甲基 - 3 - 硫代半卡巴腙）的中性单体铜（II）配合物CuL在乙腈和二甲基甲酰胺中用于金属辅助配体中心析氢的电催化行为。在过电位分别为0.80 V和0.76 V时，CuL在乙腈中的最大周转频率（TOF）为10000 s⁻¹，在二甲基甲酰胺中的最大周转频率为5100 s⁻¹。速率定律为催化剂一级反应和质子浓度二级反应。控制电位电解的气体分析证实CuL是一种电催化剂，产生H₂的最小法拉第效率为81%，周转数高达73，并且在23小时内没有降解迹象。使用氘代酸对析氢反应（HER）进行了探究，证明动力学同位素效应为7.54。质子丰度研究表明速率决定步骤涉及一个质子。使用¹H NMR、X射线光电子能谱和紫外 - 可见光谱对催化中间体进行了鉴定。所提出机制中的所有催化中间体均使用密度泛函理论计算（采用B3LYP泛函和6 - 311g(d,p)基组）成功优化，并支持所提出的机制。
