Abstract

Three Keggin polyoxotungstate inorganic–organic hybrid compounds have been synthesized under hydrothermal conditions by using H₄SiW₁₂O₄₀ as starting materials: [{Cu^II(2,2′-bipy)₂}₂SiW₁₂O₄₀]·2H₂O (1), [{Cu^II(phen)₂}₂SiW₁₂O₄₀] (2) and [{Cu^I(2,2′-bipy)₂}₄SiW₁₂O₄₀] (3) (2,2′-bipy = 2,2′-bipyridine, phen = 1,10′-phenanthroline) and structurally characterized by elemental analysis, IR spectra, TG analysis and X-ray single-crystal diffraction. Three compounds are all based on [SiW₁₂O₄₀]⁴⁻ α-Keggin type building block and synthesized under the same reaction condition, only different compound 1 and 2 ligand, 1 and 3 pH value. Compound 1 displays a novel example of two-dimensional framework with tetra-supporting α-Keggin polyanions which are linked by four same fragments and it becomes 3D structure due to the existence of hydrogen bonds. Compound 2 shows that the bi-supporting polyoxotungstate molecule consists of a α-Keggin polyoxoanion [SiW₁₂O₄₀]⁴⁻ and a pair of transition metal complex fragments which are covalently linked to opposite sides of the surface terminal oxygen atoms of WO₆ octahedra. Compound 3 consists of α-[SiW₁₂O₄₀]⁴⁻ polyoxoanions, counter cations [Cu(2,2′-bipy)₂]⁺. The crystal packing is stabilized by H-bonds and weak π–π interactions, leads to a 3D supramolecular architecture. The results show that the pH value of the reaction system plays a crucial role in structural control of self-assembled processes. The thermal stabilities of the compounds are discussed.

Graphical Abstract

Three Keggin polyoxotungstate inorganic–organic hybrid compounds have been synthesized under hydrothermal conditions by using H₄SiW₁₂O₄₀ as starting materials: [{Cu^II(2,2′-bipy)₂}₂SiW₁₂O₄₀]·2H₂O (1), [{Cu^II(phen)₂}₂SiW₁₂O₄₀] (2) and [{Cu^I(2,2′-bipy)₂}₄SiW₁₂O₄₀] (3) (2,2′-bipy = 2,2′-bipyridine, phen = 1,10′-phenanthroline) and structurally characterized by elemental analysis, IR spectra, TG analysis and X-ray single-crystal diffraction. Three compounds are all based on [SiW₁₂O₄₀]⁴⁻ α-Keggin type building block and synthesized under the same reaction condition, only different compound 1 and 2 ligand, 1 and 3 pH value.

中文翻译：

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刚性有机配体和pH值控制的三种Keggin型多聚钨酸盐衍生物：合成，晶体结构

摘要

以H ₄ SiW ₁₂ O ₄₀为起始原料，在水热条件下合成了三种Keggin聚氧钨酸盐无机-有机杂化化合物：[{Cu ^II（2,2'-bipy）₂ } ₂ SiW ₁₂ O ₄₀ ]·2H ₂ O （1），[{Cu ^II（phen）₂ } ₂ SiW ₁₂ O ₄₀ ]（2）和[{Cu ^I（2,2'-bipy）₂ } ₄ SiW ₁₂ O ₄₀ ]（3）（2,2'-bipy = 2,2'-bipyridine，phen = 1,10'-phenothroline），并通过元素分析，红外光谱，TG分析和X射线单晶衍射进行结构表征。三种化合物均基于[SiW ₁₂ O ₄₀ ] ⁴ -α-Keggin型结构单元，并且在相同的反应条件下合成，只有化合物1和2的配体不同，pH值分别为1和3。化合物1显示了具有四个相同片段相连的四支撑α-Keggin聚阴离子的二维骨架的新实例，由于存在氢键，该化合物变为3D结构。化合物2结果表明，双支撑聚氧钨酸分子由一个α-Keggin聚氧阴离子[SiW ₁₂ O ₄₀ ] ^4-和一对过渡金属络合物片段组成，这些片段共价连接到WO ₆八面体的表面末端氧原子的相对侧。化合物3由α-[SiW ₁₂ O ₄₀ ] ^4-聚氧阴离子，抗衡阳离子[Cu（2,2'-bipy）₂ ] ^+组成。晶体堆积通过H键和弱的π-π相互作用而稳定，从而导致3D超分子体系结构。结果表明，反应体系的pH值在自组装过程的结构控制中起着至关重要的作用。讨论了化合物的热稳定性。

图形概要

以H ₄ SiW ₁₂ O ₄₀为起始原料，在水热条件下合成了三种Keggin聚氧钨酸盐无机-有机杂化化合物：[{Cu ^II（2,2'-bipy）₂ } ₂ SiW ₁₂ O ₄₀ ]·2H ₂ O （1），[{Cu ^II（phen）₂ } ₂ SiW ₁₂ O ₄₀ ]（2）和[{Cu ^I（2,2'-bipy）₂ } ₄ SiW ₁₂ O ₄₀ ]（3）（2,2'-bipy = 2,2'-bipyridine，phen = 1,10'-phenothroline），并通过元素分析，红外光谱，TG分析和X射线单晶衍射进行结构表征。三种化合物均基于[SiW ₁₂ O ₄₀ ] ⁴ -α-Keggin型结构单元，并且在相同的反应条件下合成，只有化合物1和2的配体不同，pH值分别为1和3。