The water/ZnCl₂ phase diagram in the vicinity of the 75 mol % water composition is reported, demonstrating the existence of a congruently melting phase. Single crystals of this 3-equiv hydrate were grown, and the crystal structure of [Zn(OH₂)₆][ZnCl₄] was determined. Synchrotron X-ray and neutron diffraction and IR and Raman spectroscopy along with reverse Monte Carlo modeling demonstrate that a CsCl-type packing of the molecular ions persists into the liquid state. Consistent with the crystalline and liquid structural data, IR spectroscopy demonstrates that the O–H bonds of coordinated water do not exhibit strong intermolecular hydrogen ion bonding but are significantly weakened because of the water’s coordination to Lewis acidic zinc ions. The O–H bond weakening makes this system a very strong hydrogen-bond donor, whereas the ionic packing along with the nonpolar geometry of the molecular ions makes this system a novel nonpolar, hydrogen-bonding, ionic liquid solvent.

中文翻译：

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三水合氯化锌的结晶和液体结构：一种独特的离子液体

报告了水组成为75 mol％附近的水/ ZnCl ₂相图，表明存在完全熔融的相。生长该3当量水合物的单晶，并且[Zn（OH ₂）₆ ] [ZnCl ₄确定。同步加速器的X射线和中子衍射，IR和拉曼光谱以及反向蒙特卡洛模型表明，分子离子的CsCl型堆积一直保持为液态。与晶体和液体结构数据一致，IR光谱表明配位水的O–H键没有显示出强大的分子间氢离子键，但由于水与路易斯酸性锌离子的配位而被显着削弱。OH键的弱化使该系统成为非常牢固的氢键供体，而离子堆积以及分子离子的非极性几何结构使该系统成为一种新型的非极性，氢键结合的离子液体溶剂。