Influence of a bridging group and the substitution effect of bis(1,2,4-triazine) N-donor extractants on their interactions with a Np(V) cation.
Influence of a bridging group and the substitution effect of bis(1,2,4-triazine) N-donor extractants on their interactions with a Np(V) cation.
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DOI：
10.1021/ic500138w
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发表时间：
2014-07
影响因子：
4.6
通讯作者：
Xia Yang;Yan-Fang Liang;Songdong Ding;Shoujian Li;Z. Chai;Dongqi Wang
中科院分区：
文献类型：
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作者：
Xia Yang;Yan-Fang Liang;Songdong Ding;Shoujian Li;Z. Chai;Dongqi Wang
目前的理论研究提供了一个现实的评估平衡结构，反应模式，并与双形成的各种镎基配合物的成键特性，（三嗪基）N-供体萃取剂，其在它们的桥连基团如吡啶、联吡啶和邻菲咯啉方面不同，对应于三齿双（三嗪基）吡啶和四齿双（三嗪基）联吡啶和双（三嗪基）-1，10-菲咯啉（BTPhens）。计算结果表明，无论在气相、水相还是有机相中，[NpO_2]（+）与四齿配体的配位比与三齿配体的配位更有利。硝酸根离子的存在增强了镎基的配位能力，在热力学上稳定了中性的NpO_2L（NO_3）配合物。研究表明，在水-有机相界面上，络合反应模式为[NpO 2（H2O）n]（+）+ L + NO3（-）→ NpO 2 L（NO3）+nH 2 O。在配体交换反应中，邻二氮杂菲桥联基团的贡献相对于其吡啶对应物更为显著。水合镎基与C2-BTPhen和BTPhen在硝酸根离子辅助下的络合反应是有利的，这是由于配体的最小变形和强络合稳定性。原子在分子中的量子理论和电荷分解分析表明，电子离域和电荷转移是负责的四齿配合物的稳定性的主要原因，并揭示了一个强大的离子特征的Np-配体键。前沿分子轨道的检查揭示了一个独特的5 f轨道（NP）与配体原子的相互作用，这意味着F-共价的程度。该研究为合理设计配体，提高配体与Np（V）的结合能力，更有效地分离乏燃料中的Np提供了理论依据。
The present theoretical study provides a realistic evaluation of the equilibrium structure, reaction modes, and bonding characteristics of a variety of neptunyl complexes formed with bis(triazinyl) N-donor extractants, which differ in their bridging groups such as pyridine, bipyridines, and orthophenanthroline, corresponding to the ligands (L) of tridentate bis(triazinyl)pyridines and tetradentate bis(triazinyl)bipyridines and bis(triazinyl)-1,10-phenanthrolines (BTPhens), respectively. Our calculations show that coordination of [NpO2](+) to tetradentate ligands is more favorable than that to tridentate ones no matter in a gas, aqueous, or organic phase. The presence of nitrate ions can enhance the coordination ability of neptunyl and stabilize the neutral NpO2L(NO3) complexes in thermodynamics. Our studies indicate that the complexation reaction mode [NpO2(H2O)n](+) + L + NO3(-) → NpO2L(NO3) + nH2O is the most probable at the interface between water and the organic phase. The contribution of an orthophenanthroline bridging group is relatively more pronounced compared to its pyridine counterpart in ligand-exchange reaction. Complexation reactions of hydrated neptunyl with C2-BTPhen and BTPhen assisted by a nitrate ion are favorable thermodynamically, resulting from the least deformation of the ligand and strong complexation stability. The quantum theory of atoms-in-molecules and charge decomposition analysis suggest that electron delocalization and charge transfer are the main reasons responsible for stabilization of the tetradentate complexes and reveal a strong ionic feature of the Np-ligand bonds. Inspection of the frontier molecular orbitals reveals a distinct 5f orbital (Np) interaction with ligand atoms, implying the extent of f-based covalency. Our study may facilitate the rational design of ligands toward the improvement of their binding ability with Np(V) and more efficient separation of Np in spent nuclear fuels.