Institut für Energie- und Klimaforschung-Nukleare Entsorgung, und Reaktorsicherheit- (IEK-6), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Strasse 1, 52428, Jülich, Germany.
JARA High-Performance Computing, Schinkelstrasse 2, 52062, Aachen, Germany.
Chemistry. 2019 Apr 11;25(21):5507-5513. doi: 10.1002/chem.201806161. Epub 2019 Mar 20.
When considering f elements, solvent extraction is primarily used for the removal of lanthanides from ore and their recycling, as well as for the separation of actinides from used nuclear fuel. Understanding the complexation mechanism of metal ions with organic extractants, particularly the influence of their molecular structure on complex formation is of fundamental importance. Herein, we report an extraordinary (up to two orders of magnitude) change in the extraction efficiency of f elements with two diastereomers of dimethyl tetraoctyl diglycolamide (Me -TODGA), which only differ in the orientation of a single methyl group. Solvent extraction techniques, extended X-ray absorption fine structure (EXAFS) measurements, and density functional theory (DFT) based ab initio calculations were used to understand their complex structures and to explain their complexation mechanism. We show that the huge differences observed in extraction selectivity results from a small change in the complexation of nitrate counter-ions caused by the different orientation of one methyl group in the backbone of the extractant. The obtained results give a significant new insight into metal-ligand complexation mechanisms, which will promote the development of more efficient separation techniques.
在考虑 f 元素时，溶剂萃取主要用于从矿石中去除镧系元素并进行回收，以及从乏核燃料中分离锕系元素。了解金属离子与有机萃取剂的络合机制，特别是其分子结构对络合形成的影响，具有重要的基础意义。在此，我们报告了两种（R，R）-和（S，S）-二甲基四辛基二甘酰胺（Me-TODGA）的非对映异构体在萃取 f 元素时效率的显著变化（高达两个数量级），这两种异构体仅在单个甲基的取向上有所不同。我们使用溶剂萃取技术、扩展 X 射线吸收精细结构（EXAFS）测量和基于密度泛函理论（DFT）的从头算计算来了解它们的络合结构，并解释它们的络合机制。我们表明，观察到的萃取选择性的巨大差异源于在萃取剂主链中一个甲基的取向不同导致的硝酸盐反离子络合的微小变化。所得结果为金属-配体络合机制提供了重要的新见解，这将促进更有效的分离技术的发展。
