Wang Xiuli, Bai Xue, Lin Hongyan, Sun Junjun, Wang Xiang, Liu Guocheng
Department of Chemistry, Bohai University Jinzhou 121000 P. R. China
RSC Adv. 2018 Jun 20;8(40):22676-22686. doi: 10.1039/c8ra03277g. eCollection 2018 Jun 19.
Five new polyoxometalate (POM)-based metal-organic complexes (MOCs) with different rigid pyridyl-bis(triazole) ligands, namely, H{Co(Hpyttz-I)(HO)[CrMo(OH)O]}·8HO (1), {Co(Hpyttz-I)(HO)[TeMoO]}[Co(HO)]·3HO (2), {Co(Hpyttz-II)(HO)[γ-MoO]}·10HO (3), {Ni(Hpyttz-II)(HO)[γ-MoO]}·10HO (4), {Ni(Hpyttz-III)(HO)[γ-MoO]}·10HO (5) (Hpyttz-I = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, Hpyttz-II = 3-(pyrid-3-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, Hpyttz -III = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a two-dimensional (2D) supramolecular network based on the binuclear complex unit: [Co(Hpyttz-I)(HO) [CrMo(OH)O]]. Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex: {Co(Hpyttz-I)(HO)[TeMoO]}, the discrete [Co(HO)] units act as counter cations. Complexes 3 and 4 are isostructural with different center metals (M = Co or Ni), the adjacent γ-MoO anions are linked by the M ions to form a 1D M-γ-MoO inorganic chain. Then 1D M-γ-MoO inorganic chains are linked together by the 1D metal-organic M-(Hpyttz-II) chains to form a 3D framework. In complex 5, γ-MoO anions are bridged by the Ni ions to give a 1D Ni-γ-MoO inorganic chain, the adjacent 1D Ni-γ-MoO chains are connected through [Ni(Hpyttz-III)] units to form a 2D layer. The effect of POM type and coordination site of the ligands on the structures of the title complexes were discussed. The title complexes 1, 2 and 5 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid. In addition, the redox potentials of complexes 1, 2 and 5 are highly sensitive to pH and may be used as a kind of potential pH sensor.
成功合成了五种基于多金属氧酸盐（POM）的新型金属有机配合物（MOC），它们带有不同的刚性吡啶基 - 双（三唑）配体，即H{Co(Hpyttz - I)(H₂O)[CrMo(OH)O]}·8H₂O (1)、{Co(Hpyttz - I)(H₂O)[TeMoO]}[Co(H₂O)₆]·3H₂O (2)、{Co(Hpyttz - II)(H₂O)[γ - MoO₄]}·10H₂O (3)、{Ni(Hpyttz - II)(H₂O)[γ - MoO₄]}·10H₂O (4)、{Ni(Hpyttz - III)(H₂O)[γ - MoO₄]}·10H₂O (5)（Hpyttz - I = 3 - （吡啶 - 2 - 基） - 5 - （1H - 1,2,4 - 三唑 - 3 - 基） - 1,2,4 - 三唑基，Hpyttz - II = 3 - （吡啶 - 3 - 基） - 5 - （1H - 1,2,4 - 三唑 - 3 - 基） - 1,2,4 - 三唑基，Hpyttz - III = 3 - （吡啶 - 4 - 基） - 5 - （1H - 1,2,4 - 三唑 - 3 - 基） - 1,2,4 - 三唑基），并通过单晶X射线衍射、红外光谱、粉末X射线衍射（PXRD）和热重分析（TGA）对其进行了结构表征。配合物1是基于双核配合物单元[Co(Hpyttz - I)(H₂O) [CrMo(OH)O]]的二维（2D）超分子网络。配合物2是源自双核钴配合物{Co(Hpyttz - I)(H₂O)[TeMoO]}的一维超分子链，离散的[Co(H₂O)₆]单元充当抗衡阳离子。配合物3和4具有不同的中心金属（M = Co或Ni）但结构相同，相邻的γ - MoO₄阴离子通过M离子连接形成一维M - γ - MoO₄无机链。然后一维M - γ - MoO₄无机链通过一维金属有机M - （Hpyttz - II）链连接在一起形成三维框架。在配合物5中，γ - MoO₄阴离子由Ni离子桥连形成一维Ni - γ - MoO₄无机链，相邻的一维Ni - γ - MoO₄链通过[Ni(Hpyttz - III)]单元连接形成二维层。讨论了POM类型和配体的配位位点对标题配合物结构的影响。标题配合物1、2和5对溴酸盐/过氧化氢的还原以及抗坏血酸的氧化表现出优异的双功能电催化活性。此外，配合物1、2和5的氧化还原电位对pH高度敏感，可作为一种潜在的pH传感器。
