First-Principles Study of the Separation of AmIII/CmIII from EuIII with Cyanex301

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• 作者：Xiaoyan Cao ; Daniel Heidelberg ; Jan Ciupka ; Michael Dolg
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：November 15, 2010
• 年：2010
• 卷：49
• 期：22
• 页码：10307-10315
• 全文大小：832K
• 年卷期：v.49,no.22(November 15, 2010)
• ISSN：1520-510X

文摘

The experimentally observed extraction complexes of trivalent lanthanide Eu^III and actinide Am^III/Cm^III cations with purified Cyanex301 [bis(2,4,4-trimethylpentyl)dithiophosphinic acid, HBTMPDTP denoted as HL], i.e., ML₃ (M = Eu, Am, Cm) as well as the postulated complexes HAmL₄ and HEuL₄(H₂O) have been studied by using energy-consistent 4f- and 5f-in-core pseudopotentials for trivalent f elements, combined with density functional theory and second-order Møller−Plesset perturbation theory. Special attention was paid to explaining the high selectivity of Cyanex301 for Am^III/Cm^III over Eu^III. It is shown that the neutral complexes ML₃, where L acts as a bidentate ligand and the metal cation is coordinated by six S atoms, are most likely the most stable extraction complexes. The calculated metal−sulfur bond distances for ML₃ do reflect the cation employed; i.e., the larger the cation, the longer the metal−sulfur bond distances. The calculated M−S and M−P bond lengths agree very well with the available experimental data. The obtained changes of the Gibbs free energies in the extraction reactions M³⁺ + 3HL → ML₃ + 3H⁺ agree with the thermodynamical priority for Am³⁺ and Cm³⁺. Moreover, the ionic metal−ligand dissociation energies of the extraction complexes ML₃ show that, although EuL₃ is the most stable complex in the gas phase, it is the least stable in aqueous solution.