Ion Association in Lanthanide Chloride Solutions.
Ion Association in Lanthanide Chloride Solutions.
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稀土氯化物溶液中的离子缔合。
DOI：
10.1002/chem.201900945
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Finney AR
中科院分区：
文献类型：
--
作者：
Finney AR
更好地理解镧系元素（Ln）盐在水中的溶液化学将在材料加工、废物管理、元素示踪、医学和许多其他领域具有广泛的意义。鉴于政府对镧系元素供应安全的关切以及确定环境上可持续的加工路线的努力，矿物加工尤其如此。尽管做了很多努力，即使在简单的系统中，LnIII与小阴离子缔合的机制和热力学仍然不清楚。在本研究中，分子动力学（MD），使用新开发的力场，提供了新的见解LnCl 3（aq）的解决方案。力场准确地再现了Nd 3+，Gd 3+和Er 3+在水中的结构和动力学相比，使用密度泛函理论（DFT）的计算。自适应偏置分子动力学模拟表明，离子配对的机制从解离到缔合交换的变化取决于阳离子的大小。缔合热力学表明，虽然离子配对是有利的，但在低浓度下物种的平衡分布由弱结合的溶剂共享和溶剂分离的离子对主导，而不是接触离子对，调和了文献中LnIII-Cl缔合的一些对比观察。此外，我们还证明了一系列内球和外球的热力学稳定性 配位络合物是可比较的，并且阴离子与阳离子结合的动力学可以控制离子对之外的溶液形态分布。在这项工作中采用的技术提供了一个框架，其中调查更复杂的溶液化学的阳离子在水中。
A better understanding of the solution chemistry of the lanthanide (Ln) salts in water would have wide ranging implications in materials processing, waste management, element tracing, medicine and many more fields. This is particularly true for minerals processing, given governmental concerns about lanthanide security of supply and the drive to identify environmentally sustainable processing routes. Despite much effort, even in simple systems, the mechanisms and thermodynamics of LnIIIassociation with small anions remain unclear. In the present study, molecular dynamics (MD), using a newly developed force field, provide new insights into LnCl3(aq) solutions. The force field accurately reproduces the structure and dynamics of Nd3+, Gd3+and Er3+in water when compared to calculations using density functional theory (DFT). Adaptive‐bias MD simulations show that the mechanisms for ion pairing change from dissociative to associative exchange depending upon cation size. Thermodynamics of association reveal that whereas ion pairing is favourable, the equilibrium distribution of species at low concentration is dominated by weakly bound solvent‐shared and solvent‐separated ion pairs, rather than contact ion pairs, reconciling a number of contrasting observations of LnIII–Cl association in the literature. In addition, we show that the thermodynamic stabilities of a range of inner sphere and outer sphere coordination complexes are comparable and that the kinetics of anion binding to cations may control solution speciation distributions beyond ion pairs. The techniques adopted in this work provide a framework with which to investigate more complex solution chemistries of cations in water.