Abstract A set of imidazolium-based ionic liquids (ILs), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), has been synthesized and their structural and thermal behavior studied. Organic halides are well-known IL formers with imidazolium halides being the most prominent ones. Functionalization of the imidazolium cation by enhancing its hydrogen bonding capacity, i.e. through introduction of –OH groups or by diminishing it, i.e. through substitution of the ring hydrogen atoms by methyl groups is expected to change the inter-ionic interactions. Consequently, the solid-state structures of 1–3 have been characterized with means of single X-ray diffraction to shed light on preferential inter-ionic interactions for obtaining valuable information on anti-crystal engineering, i.e. designing ion combinations that favor a low melting point and exhibit a low tendency for crystallization. The study reveals that endowing IL forming ions with an enhanced hydrogen bonding capacity leads to a depression in melting points and kinetically hinders crystallization. This study provides hints towards new design concepts for IL design, similar to the common strategy of employing conformationally flexible ions.

中文翻译：

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阐明基于咪唑鎓的卤化物离子液体的结构-性能关系：晶体结构和热行为

摘要 一组基于咪唑鎓的离子液体 (IL)、1-(2-羟乙基)-3-甲基咪唑氯化物 (1)、1,3-双-(2-羟乙基)-咪唑氯化物 (2) 和 1-丁基-2,3,4,5-四甲基咪唑溴化物 (3) 已被合成并研究了它们的结构和热行为。有机卤化物是众所周知的 IL 形成剂，其中最突出的是咪唑鎓卤化物。通过增强其氢键能力，即通过引入-OH 基团或通过减少它，即通过甲基取代环氢原子，咪唑鎓阳离子的官能化有望改变离子间相互作用。最后，1-3 的固态结构已通过单次 X 射线衍射表征，以揭示优先离子间相互作用，以获得有关反晶工程的有价值信息，即设计有利于低熔点和表现出低结晶倾向。该研究表明，赋予形成离子液体的离子具有增强的氢键能力会导致熔点降低并在动力学上阻碍结晶。这项研究为 IL 设计的新设计概念提供了提示，类似于采用构象柔性离子的常见策略。该研究表明，赋予形成离子液体的离子具有增强的氢键能力会导致熔点降低并在动力学上阻碍结晶。这项研究为 IL 设计的新设计概念提供了提示，类似于采用构象柔性离子的常见策略。该研究表明，赋予形成离子液体的离子具有增强的氢键能力会导致熔点降低并在动力学上阻碍结晶。这项研究为 IL 设计的新设计概念提供了提示，类似于采用构象柔性离子的常见策略。