Glasser Leslie
Curtin Computation Group, Discipline of Chemistry, Curtin University, GPO Box U1987, Perth, West Australia 6845, Australia.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2019 Oct 1;75(Pt 5):784-787. doi: 10.1107/S2052520619010436. Epub 2019 Aug 31.
The physical properties of organic solids are altered when hydrated (and, more generally, when solvated) and this is of particular significance for pharmaceuticals in application; for instance, the solubility of a hydrate is less than that of its parent. The effective volumes of waters of crystallization for non-ionic pharmaceuticals (where the `effective' volume is the difference per water molecule between the hydrate volume and the volume of the anhydrous parent) are here examined. This investigation contrasts with our earlier study of effective volumes of waters of crystallization for ionic materials where the coulombic forces are paramount. Volumetric properties are significant since they correlate strongly with many thermodynamic properties. Twenty-nine hydrate/parent systems have been identified, and their volumetric properties are reported and analysed (apart from aspartame and ephedrine for which the structural data are inconsistent). Among these systems, the data for paracetamol are extensive and it is possible to differentiate among the volumetric properties of its three polymorphs and to quantify the effect of temperature on their volumes. The effective volumes in both ionic and non-ionic systems are similar, with a median effective volume of 22.8 Å for the non-ionic systems compared with 24.2 Å for the ionic systems, and both are smaller than the molecular volume of 30 Å of ambient liquid water - which appears to be an upper limit to the effective volumes of waters of crystallization under ambient conditions. These results will be supportive in checking and confirmation of hydrated crystal structures and in assessing their thermodynamic properties.
有机固体在水合时（更普遍地说，在溶剂化时）其物理性质会发生改变，这在药物应用中具有特别重要的意义；例如，水合物的溶解度低于其母体的溶解度。本文研究了非离子型药物结晶水的有效体积（其中“有效”体积是指水合物体积与无水母体体积之间每个水分子的差值）。这项研究与我们早期对离子材料结晶水有效体积的研究形成对比，在离子材料中库仑力起着至关重要的作用。体积性质很重要，因为它们与许多热力学性质密切相关。已确定了29个水合物/母体体系，并报告和分析了它们的体积性质（除了阿斯巴甜和麻黄碱，其结构数据不一致）。在这些体系中，对乙酰氨基酚的数据很丰富，能够区分其三种多晶型物的体积性质，并量化温度对其体积的影响。离子体系和非离子体系中的有效体积相似，非离子体系的有效体积中位数为22.8 Å，离子体系为24.2 Å，两者都小于环境液态水30 Å的分子体积——这似乎是环境条件下结晶水有效体积的上限。这些结果将有助于检验和确认水合晶体结构，并评估其热力学性质。
