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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Investigation of the structure and phase transitions of the polymeric inorganic-organic hybrids: [M(Im)4V2O6]∞ M = Mn, Co, Ni, im = imidazole
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Investigation of the structure and phase transitions of the polymeric inorganic-organic hybrids: [M(Im)4V2O6]∞ M = Mn, Co, Ni, im = imidazole

机译：聚合物无机-有机杂化物的结构和相变研究：[M（Im）4V2O6]∞M = Mn，Co，Ni，im =咪唑

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摘要

The polymeric isomorphous hybrid inorganic-organic vanadium oxide compounds [M(Im)4V2O6], M = Mn, Co, Ni, Im = imidazole, were investigated at various temperatures between 100 and 295 K by single-crystal X-ray diffraction. The crystals all contain two-dimensional polymeric sheets packed perpendicular to c*and are 1:1 disordered in the space group P42 (Z = 8) at 295 K. The disordered phase is reversibly transformed to an I41/a ordered phase (Z = 32) below 281 K for the Mn compound and below 175 K for the Co compound. Within a localized region of the I41/a phase eight imidazoles are in close proximity and seven of these are hydrogen bonded to framework O atoms. The hydrogen-bond connectivity of six of these ligands is unchanged by the phase transition that allows an inversion of the local geometry using an inversion operator that is a symmetry element of P42, but not I41/a. The Mn structure has a well defined phase transition but the Co structure shows a large hysteresis and it was necessary to include stacking faults in the modelling of the Co structure at low temperatures. The Ni structure was shown to be partially twinned, but ordered in the space group P2 (Z = 8) at 100 K, with two different localized regions each containing four pairs of inversion-related imidazoles, hydrogen bonding to framework O atoms involving eight imidazoles in one region and six imidazoles in the other. Models for the phase transition mechanisms are considered.
机译：通过单晶X射线衍射研究了聚合物同构杂化无机-有机钒氧化物化合物[M（Im）4V2O6]，M = Mn，Co，Ni，Im =咪唑，并在100至295 K的不同温度下进行了研究。晶体均包含垂直于c *堆积的二维聚合物片，在295 K的空间群P42 / n（Z = 8）中是1：1无序的。无序相可逆地转化为I41 / a有序相（对于Mn化合物，Z = 32）低于281 K;对于Co化合物，Z = 32）低于175K。在I41 / a相的局部区域内，八​​个咪​​唑非常接近，其中七个与氢原子键合在骨架O原子上。这些配体中的六个的氢键连接性通过相变而没有改变，该相变允许使用作为P42 / n对称元素而不是I41 / a的对称元素的反转算子反转局部几何形状。 Mn结构具有明确定义的相变，但Co结构显示出较大的滞后现象，因此在低温下对Co结构进行建模时必须包括堆叠缺陷。 Ni结构显示为部分孪晶，但在100 K的空间群P2 / n（Z = 8）中有序，两个不同的局部区域分别包含四对与反转有关的咪唑，氢键合到骨架O原子上一个区域中有8个咪唑，另一区域中有6个咪唑。考虑相变机制的模型。

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