Nikolaev Institute of Inorganic Chemistry , SB RAS 3, Acad. Lavrentieva avenue, Novosibirsk 630090, Russia.
J Phys Chem B. 2013 Sep 12;117(36):10677-85. doi: 10.1021/jp406082z. Epub 2013 Aug 30.
In the present work, characteristic properties of tetrabutylammonium bromide (TBAB) ionic clathrate hydrates structures were studied by single-crystal X-ray structure analysis. The structures of three different tetragonal TBAB ionic clathrate hydrates that were formed in our experiments were based on the same water lattice of tetragonal structure I (TS-I) differing in the ways of including bromide anions and arranging tetrabutylammonium cations. We demonstrated that (1) Br(-) can be included into the water lattice, replacing two water molecules, (2) the butyl group of the cation can be inserted not only in large T and P cavities but also in small D cavities of the water lattice TS-I, and (3) one of the reasons for polytypism of ionic clathrate hydrates on the basis of TS-I is the occurrence of alternative modes of arrangements of four-compartment cavities in adjacent layers of the water framework. The compositions of three TBAB ionic clathrate hydrates TBAB·38.1H2O, TBAB·32.5H2O, and TBAB·26.4H2O were determined by chemical analysis, and their enthalpies of fusion were measured by differential scanning calorimetry (DSC). From the obtained results, the enthalpies of the TBAB hydrate formation from TBAB and water were calculated thermodynamically.
在本工作中，通过单晶 X 射线结构分析研究了四丁基溴化铵（TBAB）离子包合物水合物结构的特征性质。我们实验中形成的三种不同的四方 TBAB 离子包合物水合物基于相同的四方结构 I（TS-I）的水晶格，不同之处在于溴阴离子的包含方式和四丁基铵阳离子的排列方式。我们证明了 (1) Br(-) 可以被包含在水晶格中，取代两个水分子，(2) 阳离子的丁基基团不仅可以插入大的 T 和 P 腔，还可以插入水晶格 TS-I 的小 D 腔，以及 (3) 基于 TS-I 的离子包合物水合物多型性的一个原因是水骨架相邻层中四腔的排列方式的交替模式的发生。三种 TBAB 离子包合物水合物 TBAB·38.1H2O、TBAB·32.5H2O 和 TBAB·26.4H2O 的组成通过化学分析确定，并通过差示扫描量热法（DSC）测量了它们的熔融焓。根据获得的结果，从 TBAB 和水形成 TBAB 水合物的焓从热力学上进行了计算。
