Volume and Pressure Effects for Solvation: The Case Study on Polymorphs of Neat Triiodoimidazole Replaced by Its Solvate

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• 作者：Jędrzej Marciniak ; Michał Kaźmierczak ; Kacper W. Rajewski ; Andrzej Katrusiak
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：3917-3923
• 全文大小：474K
• 年卷期：0
• ISSN：1528-7505

文摘

The formation of solvates in relation to the neat-crystal close-packing efficiency and the symmetry, involving the number of independent molecules (Z′), has been investigated. In the Cambridge Structural Database solvates are most frequent when the corresponding neat compounds have several independent molecules Z′ > 1. High pressure changes the energy difference between inequivalent molecules and their interactions, which can trigger phase transitions, solvation, multicomponent aggregation, and other transformations. When 2,4,5-triiodoimidazole (tIIm) polymorph α (Z′ = 3) was recrystallized above 0.2 GPa in methanol, a hemisolvate 2tIIm·CH₃OH was obtained. Later, the hemisolvate could be obtained at normal conditions and then polymorphs α and β disappeared, and new syntheses and recrystallizations at 0.1 MPa yielded exclusively a new polymorph γ (Z′ = 4); when dissolved in methanol it precipitates as the methanol hemisolvate only. In its structure, chains of NH···N and NH···OH···N bonded molecules are formed. These chains interact through halogen bonds, almost absent in much looser neat α-tIIm, but numerous in considerably more compact phases β and γ. The statistical distribution of the solvation effect for the crystal volume has been compared to the molecular volume calculated and measured in several ways for the most frequent solvates.