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首页> 外文期刊>Crystal growth & design >Synthesis, Crystal Structures, and Phase Transitions of Dabco Oxonium Triperchlorate and Tritetrafluoroborate
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Synthesis, Crystal Structures, and Phase Transitions of Dabco Oxonium Triperchlorate and Tritetrafluoroborate

机译：三氯氧化钴和三氟硼酸盐的合成，晶体结构和相转变

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摘要

Complexes of (C6H14N2)H3O(ClO4)(3) and (C6H14N2)H3O(BF4)(3) crystallize from strongly acidic water solutions of 1,4-diazabicyclo[2.2.2]octane. The crystals have been characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, dilatometry, and dielectric studies. Four crystalline phases of the perchlorate complex have been identified. Their highly symmetric cubic structures are diversified by the degree of structural disorder. The first-order transition to the highly disordered high temperature phase I at 387.8 K is associated with a huge entropy gain of 29.3 J mol(-1) K-1, and a jump-wise expansion of the crystal by 1.4%. The second-order transition at 295.8 K, between phases II and III, also has an order-disorder character and is associated with an unusual dielectric response related to the dipolar fluctuations induced be ordering of the oxonium cations. Phase III of the crystal transforms to the low-temperature phase IV through the first-order transition around 127 K. The terafluoroborate complex crystallizes in a topologically distinct structure of hexagonal symmetry. The crystal undergoes a second-order phase transition at 335 K. Although the transition entropy of 30 J mol(-1) K-1 clearly indicates an order disorder mechanism, the low-temperature phase II remains partly disordered even at 100 K. The substantial differences between the structures and properties of both compounds have been attributed to the different properties of the ClO4-/BF4- ions and of the O-H center dot center dot center dot O/O-H center dot center dot center dot F hydrogen bonds.
机译：（C6H14N2）H3O（CLO 4）（3）和（C6H14N2）H3O（BF4）（3）的复合物从1,4-二氮杂双环[2.2.2]辛烷的强酸性水溶液中结晶。晶体的特征在于热重分析，差示扫描量热法，X射线衍射，膨胀测定和介电研究。已经鉴定了四种高氯酸盐络合物的结晶相。它们高度对称的立方体结构是通过结构障碍程度的多样化。在387.8k的高度无序高温阶段I的一阶转变与巨大的熵增益为29.3J mol（-1）k-1，晶体的跃升膨胀为1.4％。在第II和III阶段之间的二阶转变为295.8k，也具有命令障碍特征，与与诱导的氧化恶阳离子排序的偶极波动有关的不寻常的介电响应相关。晶体的相III通过大约127k的一阶转变转变为低温相IV。甲氟硼酸盐复合物在椎间六边形对称的拓扑上不同的结构中结晶。晶体在335k处经历二阶相转变。尽管30J mol（-1）k-1的过渡熵显然表明了命令障碍机制，但即使在100k时，低温期II也仍保持部分无序。该两种化合物的结构和性质之间的显着差异已经归因于CLO4-/ BF4-离中的不同性质和OH中心点中心点中心点O / OH中心点中心点中心点F氢键。

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