Planar Cu2(ppz)2 Dimers as SBUs for Diverse Polyoxometalate-Based Metal Organic Frameworks

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• 作者：Zhi-Kai Qi ; Jun-Liang Liu ; Juan-Juan Hou ; Min-Min Liu ; Xian-Ming Zhang
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：November 5, 2014
• 年：2014
• 卷：14
• 期：11
• 页码：5773-5783
• 全文大小：864K
• ISSN：1528-7505

文摘

Five new polyoxometalate-based metal organic frameworks, [Cu₄(ppz)₄(PO₄)]路[CuBr₂] (1), [Cu₄(ppz)₄(MoO₄)₂(H₂O)]路2H₂O (2), [Cu(Hppz)(Mo₂O₇)] (3), [Cu₂(ppz)₂(Mo₃O₁₀)] (4), and [Cu₆(ppz)₆(PMo₃^VMo₉^VIO₄₀)] (5) (Hppz = 2-(1H-pyrazol-3-yl)pyrazine), have been hydrothermally synthesized and fully characterized, in which a planar Cu₂(ppz)₂ dimer acts as a secondary building unit (SBU) and provides up to six potential binding sites. In virtue of the strong Jahn鈥揟eller (JT) effect of Cu(II) ions, the potential binding sites in the Cu₂(ppz)₂ SBU can facilely be occupied by auxiliary oxygen-donor anions and/or outward pyrazine nitrogen atoms of neighboring SBUs. The auxiliary oxygen-donor anions in compounds 1鈥?b>5 range from simple phosphate and molybdate, zonal Mo₂O₇^{2鈥?/sup> and Mo₃O₁₀2鈥?/sup> to a spherical three-electron reduced Keggin anion [PMo₁₂O₄₀]6鈥?/sup>, respectively. Compound 1 contains an unprecedented 3D (4,6)-connected cationic open framework [Cu₄(ppz)₄(PO₄)]+ with 1D channels filled by linear CuBr₂鈥?/sup> anions, where the Cu₂(ppz)₂ SBUs and PO₄ groups act as nodes and the outward Cu鈥揘 bonds and oxo bridges act as linkers. 2 possesses a complicated trinodal (3,4)-connected topological framework, in which 渭₃-MoO₄ and Cu₂(ppz)₂ groups act as 3- and 4-connected nodes and the outward Cu鈥揘 bonds and double 渭₂-MoO₄ groups act as linkers. Differing from 1 and 2, compound 3 shows a 2D organic鈥搃norganic hybrid sheet constructed by a [Mo₂O₇]2鈥?/sup> ribbon of cyclic hexameric edge-shared [MoO₆]-octahedra and Cu₂(ppz)₂ SBUs. Similar to 3, compound 4 also shows 2D organic鈥搃norganic hybrid sheets constructed by zigzag [Mo₃O₁₀]2鈥?/sup> ribbons and Cu₂(ppz)₂ SBUs, and adjacent sheets are extended by weak Mo鈥揘 bonds into the 3D network. 5 has a 3D 6-connected pcu topological framework constructed by Cu₂(ppz)₂ SBUs and [PMo₁₂O₄₀]6鈥?/sup> anions, which also can be viewed as cationic of the NbO topological [Cu₆(ppz)₆]6+ network with cavities filled by [PMo₁₂O₄₀]6鈥?/sup> anions. Magnetic measurements show that there is strong antiferromagnetic coupling within the Cu₂(ppz)₂ dimer and only one unpaired electron within the three-electron reduced Keggin anion.}