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首页> 外文期刊>Crystal growth & design >Structural diversities of cobalt(II) coordination polymers with citric acid
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Structural diversities of cobalt(II) coordination polymers with citric acid

机译：钴（II）配位聚合物与柠檬酸的结构多样性

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The reactions of cobalt(II) ion with citric acid (C6H8O7 = H(4)Cit) have been studied in an acidic aqueous solution of pH 1-4, which result in the isolations of four new polymeric cobalt(II) citrate complexes: [Co(H(2)cit)-(H2O)](n) (1), [Co(H2O)(4)](n)[Co-2(Hcit)(2)(H2O)(4)](n) - 6nH(2)O (2), [Co(H2O)(6)](n)[Co(Hcit)(H2O)](2n) - 2nH(2)O (3), and (NH4)(2n)[Co-2(Hcit)(2)-(H2O)(2)](n) (4). The complexes have been characterized by spectroscopic and single crystal X-ray diffraction studies. The Co(II) ion in each complex exists in an octahedral coordination environment. The citrate ligand binds the Co(II) ion tridentately via its α-hydroxyl, α-carboxylate, and one of the β-carboxylate groups as a basic feature. The polymeric structures are constructed by the further coordination of α-carboxylate or β-carboxylate groups. Complex 1 forms a chiral helical chain running along the a-axis of the crystal via the two bridged bonded oxygen atoms of the α-carboxylate group, leaving the P-carboxylic acid group free and forming strong hydrogen bond. The dimeric cobalt(II) citrate unit [Co-2(Hcit)(2)(H2O)(4)](2-) in the complex 2 forms a one-dimensional polymeric chain through the coupling of long-arm P-carboxylate groups with the planar [Co(H2O)(4)] and [Co-2(Hcit)(2)(H2O)4] units. The [Co(Hcit)(H2O)](-) unit in complex 3 forms an infinite chain along a 21 axis. Complex 4 forms a layered complex through the links of the new dimeric unit [Co-2(Hcit)(2)(H2O)(2)] by the oxygen atoms of the P-carboxylate groups. Interconversions between 1, 3, and 4 are found to be pH- and counterion-dependent. Heating of coordination polymer 2 results in the irreversible formation of 3. The structural diversities of these cobalt(II) citrate polymers demonstrate that pH, counterions, and reaction temperature play essential roles in the formations of such one-dimensional and two-dimensional frameworks.
机译：已在pH 1-4的酸性水溶液中研究了钴（II​​）离子与柠檬酸（C6H8O7 = H（4）Cit）的反应，这导致分离出四种新的柠檬酸钴（II）聚合复合物： [Co（H（2）cit）-（H2O）]（n）（1），[Co（H2O）（4）]（n）[Co-2（Hcit）（2）（H2O）（4）] （n）-6nH（2）O（2），[Co（H2O）（6）]（n）[Co（Hcit）（H2O）]（2n）-2nH（2）O（3）和（NH4 ）（2n）[Co-2（Hcit）（2）-（H2O）（2）]（n）（4）。配合物已通过光谱学和单晶X射线衍射研究表征。每个络合物中的Co（II）离子都存在于八面体配位环境中。柠檬酸酯配体通过其α-羟基，α-羧酸根和一个β-羧酸根基团之一作为三齿键合Co（II）离子。通过α-羧酸根或β-羧酸根基团的进一步配位来构造聚合物结构。配合物1形成α-手性螺旋链，通过α-羧酸根基团的两个桥连的键合氧原子沿着晶体的a-轴延伸，使P-羧酸基团游离并形成强氢键。配合物2中的二聚柠檬酸钴（II）单元[Co-2（Hcit）（2）（H2O）（4）]（2-）通过长臂P-羧酸酯的偶联形成一维聚合物链平面[Co（H2O）（4）]和[Co-2（Hcit）（2）（H2O）4]单元的组合。配合物3中的[Co（Hcit）（H2O）]（-）单元沿21轴形成无限链。配合物4通过新的二聚体单元[Co-2（Hcit）（2）（H2O）（2）]与P-羧酸酯基团的氧原子连接形成层状配合物。发现1、3和4之间的相互转换取决于pH和抗衡离子。加热配位聚合物2导致不可逆地形成3。这些柠檬酸钴（II）聚合物的结构多样性表明，pH，抗衡离子和反应温度在此类一维和二维骨架的形成中起着至关重要的作用。

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