Sahil Sha Tamanna, McCardle Kaitlin M, Le Magueres Pierre, Panetier Julien A, Jurss Jonah W
Department of Chemistry and Biochemistry, University of Mississippi, University, Mississippi 38677, United States.
Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902, United States.
ACS Omega. 2024 Jul 31;9(32):34555-34566. doi: 10.1021/acsomega.4c02520. eCollection 2024 Aug 13.
A copper complex supported by a redox-active bipyridyl--heterocyclic carbene based ligand framework is reported. From X-ray crystallography, the tetradentate macrocycle provides a distorted square planar geometry around the copper metal center. The complex was investigated for the electrocatalytic CO reduction reaction (CORR) in acetonitrile solutions. Electronic structure calculations were performed on the complex and associated intermediates to provide a fundamental understanding of the metal-ligand redox chemistry and are compared to the previously reported nickel and cobalt analogues. Unlike its predecessors, which are active catalysts for the CORR, the copper complex decomposes under reducing conditions in the presence of CO. A novel decomposition route involving coordination of CO to an -heterocyclic carbene (NHC) donor of the macrocyclic ligand is proposed based on density functional theory (DFT) calculations, which is supported by isolation of a putative ligand-CO adduct from the electrolyzed solution and its characterization by H NMR spectroscopy and mass spectrometry. The noninnocent behavior of the NHC donors presented here may have important implications for the stability and reactivity of other complexes supported by -heterocyclic carbenes, and further suggests that cooperative and productive pathways involving metal-bound NHCs could be exploited for CO reduction.
报道了一种由氧化还原活性联吡啶-杂环卡宾基配体框架支撑的铜配合物。通过X射线晶体学研究发现，四齿大环在铜金属中心周围提供了一种扭曲的平面正方形几何结构。对该配合物在乙腈溶液中的电催化CO还原反应（CORR）进行了研究。对该配合物及相关中间体进行了电子结构计算，以深入了解金属-配体氧化还原化学，并与先前报道的镍和钴类似物进行了比较。与其作为CORR活性催化剂的前体不同，该铜配合物在CO存在的还原条件下会分解。基于密度泛函理论（DFT）计算，提出了一种涉及CO与大环配体的-杂环卡宾（NHC）供体配位的新型分解途径，从电解溶液中分离出假定的配体-CO加合物并通过1H NMR光谱和质谱对其进行表征，为该途径提供了支持。本文中NHC供体的非单纯行为可能对其他由-杂环卡宾支撑的配合物的稳定性和反应性具有重要意义，并进一步表明涉及金属结合NHC的协同和有效途径可用于CO还原。
