The hydration structure of Cu2+: more tetrahedral than octahedral?
The hydration structure of Cu2+: more tetrahedral than octahedral?
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DOI：
10.1039/c3ra42400f
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发表时间：
2013-01-01
期刊：
影响因子：
3.9
通讯作者：
Diaz-Moreno, Sofia
中科院分区：
文献类型：
--
作者：
Bowron, Daniel T.;Amboage, Monica;Diaz-Moreno, Sofia
综合性的多技术方法已被用来解决 Cu2+ 水离子水化壳的首选几何形式这一有争议的问题。 H/D 同位素取代中子散射和 X 射线散射的组合已用于细化 Cu(ClO4)(2) 0.5 m 和 2.0 m 溶液的原子模型，该模型也被限制为同时再现通过 X 射线吸收光谱获得的阳离子环境的详细局部结构信息。采用经验潜在结构细化（EPSR）技术作为单一统一的分析框架，最大限度地减少了结果偏向于特定的预先设想的结果的机会。结果与每个 Cu2+ 离子 4.5 +/- 0.6 个水分子的平均配位一致，与 2.0 m 溶液中五重配位的最新图片相匹配，但有趣的是，这项综合研究强调，发现离子位点的首选局部几何形状具有四面体、三角双锥体和八面体成分的混合特征。还需要注意的一点是，这个新模型为文献中一个很大程度上被忽视的结果提供了支持，该结果与在玻璃状 Cu2+ 配合物的电子顺磁共振光谱中观察到的线性电场效应引起的 g 位移有关（Peisach 和 Mims, Chem. Phys. Lett., 1976, 37, 307-310），该结果首先强调了阳离子水合壳层结构中四面体扭曲的重要性。
A comprehensive multi-technique approach has been used to address the controversial question of the preferred geometric form of the Cu2+ aqua-ion hydration shell. A combination of H/D isotopic substitution neutron scattering and X-ray scattering has been used to refine atomistic models of 0.5 m and 2.0 m solutions of Cu(ClO4)(2), that have also been constrained to simultaneously reproduce detailed local structure information about the cation environment obtained by X-ray Absorption spectroscopy. The adoption of the Empirical Potential Structure Refinement (EPSR) technique as a single unified analytical framework minimises the chances for biasing the result in favour of a specific pre-conceived outcome. The results are consistent with an average coordination for each Cu2+ ion of 4.5 +/- 0.6 water molecules that matches the more recent picture of five-fold coordination in a 2.0 m solution, but interestingly this combined study highlights that the preferred local geometry of the ion sites is found to have a mixed character of tetrahedral, trigonal bipyramidal and octahedral components. A further point to note is that this new model adds support to a largely ignored result in the literature relating to the linear electric field effect induced g-shifts observed in the electron paramagnetic resonance spectra of glassy Cu2+ complexes (Peisach and Mims, Chem. Phys. Lett., 1976, 37, 307-310) that first highlighted the importance of tetrahedral distortions in the cation's hydration shell structure.