Spacer-Dependent Structural and Physicochemical Diversity in Copper(II) Complexes with Salicyloyl Hydrazones: A Monomer and Soluble Polymers

Complexation of copper(II) with a series of heterodonor chelating Schiff bases (LL) of salicylic acid hydrazide and aliphatic or cycloaliphatic ketones affords soluble one-dimensional (1D) metallopolymers containing Schiff bases as bridging ligands. Single-crystal X-ray diffraction results reveal nanometer-sized metallopolymeric wires [Cu(μ-LL)2]n with off-axis linkers and a zigzag geometry. Octahedrally coordinated copper centers, exhibiting a Jahn−Teller distortion, are doubly bridged by two Schiff-base molecules in the μ2−η1,η2 coordination mode. The use of dibutylketone with long alkyl chains as a component for Schiff base formation leads to a distorted square planar monomeric copper(II) complex [Cu(LL)2], as evidenced by its X-ray crystal structure. The compounds are characterized by elemental analyses and IR and UV−vis spectroscopy, as well as magnetic susceptibility and cyclic voltammetry measurements. Electrochemical studies on the complexes reveal an existence of polymeric and monomeric forms in solution and the dependence of Cu(II)/Cu(I) reduction potentials on alkyl groups of salicyloyl hydrazone ligands. Polymeric complexes form conducting films on Pt electrodes upon multicycle potential sweeps.

将铜(II)与一系列由水杨酸酰肼（salicylic acid hydrazide）与脂肪族或脂环族酮缩合得到的杂供体螯合席夫碱（Schiff base）配体（记为LL）进行络合反应，可得到以席夫碱为桥联配体的可溶性一维（1D）金属聚合物。单晶X射线衍射结果显示，该类纳米级金属聚合物线状物的化学式为[Cu(μ-LL)₂]ₙ，其桥联配体偏离轴线且呈现锯齿形几何构型。带有姜-泰勒畸变（Jahn-Teller distortion）的八配位铜中心，通过两个以μ₂-η¹,η²配位模式结合的席夫碱分子实现双重桥联。当使用带有长烷基链的二丁基酮（dibutylketone）作为缩合组分制备席夫碱时，会得到扭曲平面正方形构型的单核铜(II)配合物[Cu(LL)₂]，该结构已通过X射线晶体衍射得到验证。所有目标化合物均通过元素分析、红外（IR）光谱、紫外-可见（UV-vis）光谱、磁化率测试以及循环伏安法完成表征。对该类配合物的电化学研究表明，溶液中同时存在聚合物与单核两种存在形式，且Cu(II)/Cu(I)的还原电位与水杨酰腙（salicyloyl hydrazone）配体的烷基取代基团密切相关。在多轮电势扫描过程中，聚合物类配合物可在铂（Pt）电极表面形成导电薄膜。