X-ray investigation of the coordination and complex formation of lanthanoid ions in aqueous perchlorate and selenate solutions
X-ray investigation of the coordination and complex formation of lanthanoid ions in aqueous perchlorate and selenate solutions
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X 射线研究高氯酸盐和硒酸盐水溶液中镧系离子的配位和络合物形成
DOI：
10.1021/ic00213a035
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发表时间：
1985
影响因子：
4.6
通讯作者：
H. Wakita
中科院分区：
文献类型：
--
作者：
G. Johansson;H. Wakita
本文用X射线散射法测定了某些三价镧系元素（Er，Tb，Sm，La）在高氯酸盐和硒酸盐水溶液中的配位和配合物的形成。用钇作取代基的同晶取代法分析了离子半径与Y ~（3+）相近的Er ~（3+）和Tb ~（3+）的数据。内球复合物与硒酸根离子形成。Ln-O-Se的夹角约为140 °，这对应于单齿键合。在高氯酸盐溶液中没有发现内球络合物形成的迹象。数据与溶液中的配位数8一致。高氯酸盐和硒酸盐溶液中相应的Ln-H2O距离的均方根变化（与计算峰比较确定）分别为0.09和0.11 μ m。第二个配位球在RDFs中被清楚地指出。溶液中镧系元素离子的配位一直是大量研究的主题，但结果往往是矛盾的。在水溶液中得到的水合数的值似乎取决于所用的方法，1· 2和研究的复杂的形成热力学和运输性质和光谱方法往往导致不同的结果，形成的内部或外部的球复合物。3.衍射法能直接给出溶液中原子间距离及其频率的信息，已用于水化数的研究，但几乎不用于络合物形成的研究。在早期的氯化铒和碘化铒溶液的X射线衍射研究中，Brady 4估计Er 3+的水合数约为6。Wertz和同事5 6 - 7在浓缩的氯化物和溴化物溶液中发现整个系列的值为8.0。Ha-benschuss和Spedding 8在3 M氯化物溶液中用X射线散射法测定了La ~（3+）~ Nd ~（3+）为九配位，Tb ~（3+）~ Lu ~（3+）为八配位，而Nd ~（3+）~ Tb ~（3+）为中间配位。中子衍射研究的neo-Cl 2氯化物溶液与使用同位素取代导致8.5±0.2水分子在第一配位球。9这些研究中的X射线数据是通过使用第一个峰从径向分布函数分析的，用于估计水合数，假设没有内球。
The coordination and complex formation of some three-valent lanthanoids (Er, Tb, Sm, La) in aqueous perchlorate and selenate solutions have been determined from X-ray scattering measurements. Isomorphous substitution withyttrium as the substituent was used for the analysis of the data for Er3+ and Tb3+, which have ionic radii close tothat of Y3+. Inner-sphere complexes are formed with the selenate ion. The Ln-O-Se angle is about 140, which corresponds to monodentate bonding. No indication of inner-sphere complex formation is found in the perchlorate solutions. The data are consistent with a coordination number of 8 in the solutions. The root-mean-square variations in the corresponding Ln-H20 distances, as determined from comparisons with calculated peaks, are 0.09 and 0.11 Á for the perchlorate and the selenate solutions, respectively. A second coordination sphere is clearly indicated in the RDFs.The coordination of the lanthanoid ions in solution has been the subject of a large number of investigations, but the results have often been contradictory. Values obtained for hydration numbers in aqueous solution seem to depend on the method used, 1· 2 and studies of complex formation by thermodynamic and transport properties and by spectroscopic methods often lead to different results as to the formation of inner-or outer^ sphere complexes. 3 Diffraction methods, which can give direct information on in-teratomic distances and their frequencies in solution, have been used in some investigations of the hydration numbers but hardly at all for the study of complex formation. In an early X-ray diffractionstudy of erbium chloride and iodide solutions Brady4 estimated the hydration number for Er3+ to be about 6. Wertz and co-workers5 6" 7 found a value of 8.0 throughout the series in concentrated chloride and bromide solutions. Ha-benschuss and Spedding8 determined fromX-ray scattering measurements in 3 M chloride solutions that the ionsLa3+ through Nd3+ are nine-coordinated and those from Tb3+ to Lu3+ are eight-coordinated, while those between Nd3+ and Tb3+ have intermediate values. A neutron diffraction investigation of neo-dymium chloride solutions with use of isotopic substitution led to 8.5±0.2 water molecules in the first coordination sphere. 9 The X-ray data in these investigations were analyzed from the radial distribution functions by using the first peak for an estimation of the hydration number, assuming that no inner-sphere