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首页> 外文期刊>Zeitschrift fur Naturforschung. A, A journal of physical sciences >Structure of the Solvated Strontium and Barium Ions in Aqueous, Dimethyl Sulfoxide and Pyridine Solution, and Crystal Structure of Strontium and Barium Hydroxide Octahydrate
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Structure of the Solvated Strontium and Barium Ions in Aqueous, Dimethyl Sulfoxide and Pyridine Solution, and Crystal Structure of Strontium and Barium Hydroxide Octahydrate

机译：水溶液，二甲基亚砜和吡啶溶液中溶解的锶和钡离子的结构以及八水合锶和氢氧化钡的晶体结构

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Single crystal X-ray data, collected at 298 K, are used to redetermine the crystal structure of the non-isomorphic compounds [Sr(H_2O)_8](OH)_2 and [Ba(H_2O)_8](OH)_2. The eight water oxygen atoms form distorted Archimedean antiprisms around the octahydrated metal ions with mean metal ion-oxygen distances 2.62 and 2.79 A for strontium and barium, respectively. A second coordination shell of 24 hydrogen-bonded oxygen atoms with mean metal ion-oxygen distances M • • • O~Ⅱ 4.76 and 4.80 A, respectively, is observed. The hydroxide ions in both structures have an unusual hydrogen bond arrangement with 5 bonds accepted and one donated. The structure of the solvated strontium and barium ions in aqueous, dimethyl sulfoxide and pyridine solutions has been studied by means of large angle X-ray scattering and extended X-ray absorption fine structure spectroscopy techniques. In aqueous solution independent determinations of the first-sphere metal-oxygen coordination by the two techniques resulted in the bond lengths Sr-O 2.63 (2) and Ba-O 2.81 (3) A, and for both metal ions a hydration number of 8.1 (3). The second coordination spheres are very diffuse with only about 13 water molecules at similar M • • • O~Ⅱ distances as in the crystal structures and 2-3 water molecules closer to the metal ions. In dimethyl sulfoxide solution both ions were found to coordinate 6.0 (5) solvent molecules with the distances Sr-O 2.54 (1), Sr • • • S 3.77 (1) A, and Ba-O 2.76 (1), Ba • • • S 3.99 (1) A. For the solvated ions in pyridine solution EXAFS measurements yielded the distances Sr-N 2.57 (2) and Ba-N 2.78 (3) A, with a probable solvation number of 6. Correlations of hydration enthalpies and partial molar volumes with experimental M-O bond distances in aqueous solution are used to discuss hydration numbers and bond character for all of the alkaline earth metal ions.
机译：在298 K处收集的单晶X射线数据用于重新确定非同构化合物[Sr（H_2O）_8]（OH）_2和[Ba（H_2O）_8]（OH）_2的晶体结构。八个水氧原子在八水合金属离子周围形成扭曲的阿基米德反棱镜，锶和钡的平均金属离子-氧气距离分别为2.62和2.79A。观察到第二个由24个氢键合的氧原子构成的第二配位壳，金属离子-氧的平均距离M•••O〜Ⅱ分别为4.76和4.80A。两种结构中的氢氧根离子都有不同寻常的氢键排列，其中5个键被接受并且一个键被提供。借助大角度X射线散射和扩展X射线吸收精细结构光谱技术研究了水溶液，二甲基亚砜和吡啶溶液中锶和钡离子的结构。在水溶液中，通过两种技术独立测定第一球的金属氧配位，键长分别为Sr-O 2.63（2）和Ba-O 2.81（3）A，并且对于两种金属离子而言，其水合数均为8.1 （3）。第二配位球非常分散，只有大约13个水分子处于与晶体结构相似的M•••O〜Ⅱ距离，而2-3个水分子更接近金属离子。在二甲亚砜溶液中，发现两个离子都与6.0（5）个溶剂分子配位，其距离为Sr-O 2.54（1），Sr••S 3.77（1）A和Ba-O 2.76（1），Ba•• •S 3.99（1）A。对于吡啶溶液中的溶剂化离子，EXAFS测量得出距离Sr-N 2.57（2）和Ba-N 2.78（3）A，可能的溶剂化数为6。水合焓与在水溶液中具有实验MO键距离的部分摩尔体积用于讨论所有碱土金属离子的水合数和键特性。

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