pH-Dependent syntheses of copper–quinoxaline–polyoxotungatate hybrids: variable role of Keggin-type polyanion in different pH conditions
pH-Dependent syntheses of copper–quinoxaline–polyoxotungatate hybrids: variable role of Keggin-type polyanion in different pH conditions
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DOI：
10.1039/c2ce06327a
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发表时间：
2012-04
期刊：
影响因子：
3.1
通讯作者：
Yingnan Chi;Feng-Yun Cui;Ai-Rui Jia;Xiaoyue Ma;Chang-Wen Hu
中科院分区：
文献类型：
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作者：
Yingnan Chi;Feng-Yun Cui;Ai-Rui Jia;Xiaoyue Ma;Chang-Wen Hu
以keggin型多金属氧酸盐为基础，水热合成了4种新型杂化物，分别为（Hbm）3（PW12O40）·4H2O (1) （bm =苯并咪唑，由喹啉原位合成）、[Cu6(qx)9(PW12O40)2](2)、[Cu3(qx)5(PW12O40)(H2O)](3)和[Cu4(qx)4(HPCuIIW11O39)]·1.5H2O (4) （qx =喹啉）。在1中，[PW12O40]3−(PW12)簇仅作为反阴离子，并通过静电相互作用与质子化有机配体结合。在2中，以PW12为模板形成63拓扑二维层。在3中，PW12阴离子通过Cu-O弱相互作用与四个金属有机链连接，构建三维框架。在图4中，Cu(II)-取代的Keggin单元作为六齿无机配体，与来自金属有机链的四个Cu(I)离子和来自相邻pom的两个O原子配位，形成三明治状的二维层。化合物1 ~ 4的结构差异表明，自组装过程具有pH依赖性，keggin型POM在不同的pH条件下发挥不同的作用。
Four new hybrids based on the Keggin-type polyoxometalate, formulated as (Hbm)3(PW12O40)·4H2O (1) (bm = benzimidazole, which is synthesized in situ by quinoxaline), [Cu6(qx)9(PW12O40)2] (2), [Cu3(qx)5(PW12O40)(H2O)] (3) and [Cu4(qx)4(HPCuIIW11O39)]·1.5H2O (4) (qx = quinoxaline), were hydrothermally synthesized and structurally characterized by routine techniques and single-crystal X-ray diffraction. In 1, the [PW12O40]3− (PW12) clusters only act as counteranions and combine with the protonated organic ligand by electrostatic interactions. In 2, a 63 topological 2D layer is formed with the PW12 as the template. In 3, the PW12 anions link with four metal–organic chains via Cu–O weak interactions to construct a 3D framework. In 4, the Cu(II)-substituted Keggin unit as a hexadentate inorganic ligand coordinates with four Cu(I) ions from metal–organic chains and two O atoms from neighboring POMs to form a sandwich-like 2D layer. The structure difference of compounds 1–4 reveals that the self-assembly process is pH-dependent and the Keggin-type POM plays different role in different pH conditions.