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首页> 外文期刊>Crystal growth & design >Crystal Structures and Thermodynamic Properties of Polymorphs and Hydrates of Selected 2-Pyridinecarboxaldehyde Hydrazones
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Crystal Structures and Thermodynamic Properties of Polymorphs and Hydrates of Selected 2-Pyridinecarboxaldehyde Hydrazones

机译：2-吡啶甲醛Hy的多晶型物和水合物的晶体结构和热力学性质

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摘要

Synthesis, crystal structure, and thermal, behavior studies of different solid-state forms of two new 2-pyridinecarboxaldehyde N-acylhydrazones are reported together with the corresponding computational analyses. Both compounds exist in two anhydrous polymorphic forms, and crystallize also as hydrates. All of the studied crystals were obtained via solvent evaporation from solutions. Structural features were determined using single-crystal XRD (employing the transferred aspherical atom model, TAAM) supported by solid-state NMR. The relative stability of different Crystal forms was examined experimentally using, the TGA-DSC methods and supplemented with extended lattice and interaction energy calculations and crystal entropy estimation. The results confirmed the prevalent role of strong hydrogen bonds of N-H center dot center dot center dot O and N-H center dot center dot center dot N type in stabilization of anhydrous crystals. In the case of hydrates, water molecules incorporated into the crystal network are involved in the most efficient hydrogen bonds contributing significantly to the crystal cohesive energy. The TG-DSC studies showed that the denser polymorphic forms are More thermodynamically stable at higher temperatures, and excluded any thermal events before the melting point in the case of anhydrous crystals. Energy and entropy calculations were confronted with the experimental thermodynamic results.
机译：报道了两种新型2-吡啶甲醛N-酰基hydr的不同固态形式的合成，晶体结构和热行为研究，以及相应的计算分析。两种化合物均以两种无水多晶型形式存在，并且也以水合物形式结晶。所有研究的晶体都是通过从溶液中蒸发溶剂获得的。使用由固态NMR支持的单晶XRD（采用转移的非球面原子模型，TAAM）确定结构特征。使用TGA-DSC方法对不同晶体形式的相对稳定性进行了实验检查，并补充了扩展的晶格和相互作用能计算以及晶体熵估计。结果证实了N-H中心点中心点中心点O和N-H中心点中心点中心点N型的强氢键在稳定无水晶体中的普遍作用。在水合物的情况下，掺入晶体网络的水分子会参与最有效的氢键，从而大大促进晶体的内聚能。 TG-DSC研究表明，致密的多晶型物在较高温度下具有更高的热力学稳定性，对于无水晶体，它排除了熔点之前的任何热事件。能量和熵的计算面临着实验热力学结果。

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