Thermodynamic study on the complexation of Am(III) and Eu(III) with tetradentate nitrogen ligands: a probe of complex species and reactions in aqueous solution.
Thermodynamic study on the complexation of Am(III) and Eu(III) with tetradentate nitrogen ligands: a probe of complex species and reactions in aqueous solution.
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DOI：
10.1021/jp206793f
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发表时间：
2012-01
期刊：
影响因子：
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通讯作者：
J. Lan;W. Shi;Li-yong Yuan;Yi-Xiao Feng;Yu-liang Zhao;Z. Chai
中科院分区：
文献类型：
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作者：
J. Lan;W. Shi;Li-yong Yuan;Yi-Xiao Feng;Yu-liang Zhao;Z. Chai
用相对论量子力学方法研究了三价金属离子（M = Am（III），Eu（III））与四齿配体（L），6，6 '-双（5，6-二烷基-1，2，4-三嗪-3-基）-2，2'-联吡啶（BTBPs）的配位作用.在不同的反离子如NO（3）（-）、Cl（-）和ClO（4）（-）存在下，探索了内球BTBPs复合物的结构和稳定性。根据我们的计算，Am（III）和Eu（III）最多可以螯合8或9个水分子，而更稳定的物种，如M（NO（3））（3）（H（2）O）（4），在硝酸根离子存在下倾向于形成。根据我们的计算，BTBPs复合物的内球可以容纳四个水分子或三个硝酸根离子，形成诸如[ML（H（2）O）（4）]（3+）和ML（NO（3））（3）的物种。与Eu（III）配合物相比，Am（III）配合物在气相和溶液中的结合能都明显降低。此外，溶剂效应显著降低了BTBPs复合物的结合能。结果表明，产物和反应物具有相同或相近数量的硝酸根离子的络合反应更有利于BTBPs络合物的形成。总之，M（NO（3））（3）（H（2）O）（4）→ ML（NO（3））（3）和[M（NO（3））（H（2）O）（7）]（2+）→ [ML（2）（NO（3））]（2+）可能是Am（III）/Eu（III）分离过程中的主要反应。
A thermodynamic investigation has been performed to study the complexation of trivalent metal (M) ions (M = Am(III), Eu(III)) with tetradentate ligands (L), 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs), by using relativistic quantum mechanical calculations. The structures and stabilities of the inner-sphere BTBPs complexes were explored in the presence of various counterions such as NO(3)(-), Cl(-), and ClO(4)(-). According to our calculations, Am(III) and Eu(III) can chelate eight or nine water molecules at most, whereas more stable species like M(NO(3))(3)(H(2)O)(4) tend to be formed in the presence of nitrate ions. The inner sphere of the BTBPs complexes can accommodate four water molecules or three nitrate ions based on our calculations, forming species such as [ML(H(2)O)(4)](3+) and ML(NO(3))(3). Compared with Eu(III) complexes, the Am(III) counterparts have obviously lower binding energies in both the gas phase and solution. In addition, the solvent effect significantly decreases the binding energies of the BTBPs complexes. It has been found that the complexing reactions, in which products and reactants possess the same or close number of nitrate ions, are more favorable for formation of the BTBPs complexes. In short, the reactions of M(NO(3))(3)(H(2)O)(4) → ML(NO(3))(3) and [M(NO(3))(H(2)O)(7)](2+) → [ML(2)(NO(3))](2+) are probably the dominant ones in the Am(III)/Eu(III) separation process.