Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii Prosp. 31, 119991 Moscow, Russia.
The Casali Center of Applied Chemistry, The Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Molecules. 2020 Dec 23;26(1):26. doi: 10.3390/molecules26010026.
Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. HO always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of HO compared to water and the conformational mobility of HO. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of HO molecules, HO and water molecules, and HO and halogen anions. HO can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to HO/HO isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.
尽管尿素过氧化物（过碳酰胺）和过碳酸钠具有重要的技术意义，并且人们对过氧化物的固态形式越来越关注，但到 2000 年，已知的过氧溶剂合物还不到 45 种。然而，近年来 X 射线衍射仪的进步使过去 20 年中结构确定的过氧溶剂合物的数量增加了两倍以上，甚至可以进行能量解释，并深入了解过氧溶剂合物的稳定性。迄今为止，已经解析了 134 种结晶过氧溶剂合物，这些数据足以证明对该主题进行第一篇综述文章是合理的。在综述的第一章中，对结构数据库进行了全面分析，揭示了结晶过氧溶剂合物中共形成物的性质。在大多数情况下，共形成物可以分为三类：（1）无机和羧酸盐；（2）氨基酸、肽和相关两性离子；（3）具有孤对电子的氮和/或氧原子的分子化合物。综述的第二章专门讨论过氧溶剂合物中的氢键。数据库搜索和能量统计揭示了分子间氢键（氢键）的重要性，氢键在考虑的晶体中起着结构导向的作用。HO 总是作为质子供体形成两个氢键，其能量高于在同构结晶水合物中存在的类似氢键的能量。这种现象是由于与水相比，HO 的酸性更高，并且 HO 的构象更灵活。结晶过氧溶剂合物中的 H-O-O-H 二面角从 20 到 180°变化。结果，形成了由 HO 分子、HO 和水分子以及 HO 和卤素阴离子组成的无限氢键 1D 链簇。HO 可以作为质子受体形成多达四个氢键。综述的第三章专门讨论了能量计算，特别是具有周期性边界条件的密度泛函理论。详细考虑了这些方法，使人们能够获得晶体中的氢键能量。DFT 计算更深入地了解了过氧溶剂合物的稳定性，并解释了为什么过碳酰胺和过碳酸钠对 HO/HO 同构转化稳定。综述最后描述了结晶过氧溶剂合物合成的主要现代趋势，特别是高能化合物的过氧溶剂合物的生产和具有防腐和镇痛作用的混合药物形式。
