六价Act系元素与两种二吡啶甲酸衍生物络合的结构和稳定性趋势：实验和理论研究,Inorganic Chemistry

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六价Act系元素与两种二吡啶甲酸衍生物络合的结构和稳定性趋势：实验和理论研究
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2019-08-22 00:00:00 , DOI: 10.1021/acs.inorgchem.9b01629
Pingping Wei ₁ , Ning Pu ₁ , Xue Dong ₁ , Jianhua Yuan ₁ , Youzhen Li ₁ , Lei Xu ₁ , Jing Chen ₁ , Chao Xu ₁

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揭示溶液中高价act系元素的络合行为对于更好地了解act系元素的基本化学性质以及控制核燃料循环中act系元素的分离特性具有十分重要的意义。在这项工作中，六价act离子阳离子U（VI），Np（VI）和Pu（VI）与两种二吡啶甲酸衍生物，6-（二甲基氨基甲酰基）吡啶甲酸（DMAPA，表示为HL）和N ²，N络合²，N ⁶，N ⁶通过吸收分光光度法，X射线晶体学和DFT计算研究了水溶液中的-四甲基吡啶-2,6-二甲酰胺（TMPDA）。鉴定了U（VI），Np（VI）和Pu（VI）与DMAPA形成的1/1和1/2（金属：配体）配合物，并确定了相应的稳定性常数。三种六价act系阳离子与DMAPA的结合强度在1/1/2和1/2配合物中均遵循U（VI）> Np（VI）> Pu（VI）的顺序，这表明络合的驱动力主要是静电相互作用。此外，已经建立了吸收光谱的特征与Pu（VI）和Np（VI）与DMAPA配合物的对称性之间的关系。1/2 U（VI）/ DMAPA配合物的晶体结构以及An（VI）/ DMAPA配合物的DFT优化结构为六价act系阳离子配合物的结构特征提供了更多启示。与DMAPA相比，TMPDA与水溶液中的三个六价act系阳离子没有可观察到的络合作用，这可能归因于TMPDA供体原子上的低电子密度以及二甲基氨基甲酰基的空间位阻效应，如DFT计算所证实的那样。这项工作的结果为水溶液中六价act系阳离子的络合趋势提供了新的见解。TMPDA与水溶液中的三个六价act系阳离子没有表现出可观察到的络合，这可能归因于TMPDA供体原子上的低电子密度以及DFT计算所阐明的二甲基氨基甲酰基的空间位阻效应。这项工作的结果为水溶液中六价act系阳离子的络合趋势提供了新的见解。TMPDA与水溶液中的三个六价act系阳离子没有表现出可观察到的络合，这可能归因于TMPDA供体原子上的低电子密度以及DFT计算所阐明的二甲基氨基甲酰基的空间位阻效应。这项工作的结果为水溶液中六价act系阳离子的络合趋势提供了新的见解。

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Structural and Stability Trends of the Complexation of Hexavalent Actinides with Two Dipicolinic Acid Derivatives: An Experimental and Theoretical Study

Revealing the complexation behavior of high-valent actinides in solutions is of great importance to better understand the fundamental chemistry of actinides as well as to control the separation property of actinides in nuclear fuel cycles. In this work, the complexation of hexavalent actinide cations U(VI), Np(VI), and Pu(VI) with two dipicolinic acid derivatives, 6-(dimethylcarbamoyl)picolinic acid (DMAPA, denoted as HL) and N²,N²,N⁶,N⁶-tetramethylpyridine-2,6-dicarboxamide (TMPDA), in aqueous solutions were investigated by absorption spectrophotometry, X-ray crystallography, and DFT calculations. Formation of 1/1 and 1/2 (metal:ligand) complexes of U(VI), Np(VI), and Pu(VI) with DMAPA were identified and the corresponding stability constants were determined. The binding strengths of the three hexavalent actinide cations with DMAPA follow the order of U(VI) > Np(VI) > Pu(VI) in both 1/1 and 1/2 complexes, indicating that the driving force for the complexation is mainly electrostatic interactions. In addition, the relationships between the features of the absorption spectra and the symmetry of Pu(VI) and Np(VI) complexes with DMAPA have been established. The crystal structure of the 1/2 U(VI)/DMAPA complex as well as the DFT optimized structures of An(VI)/DMAPA complexes shed additional light on the structural characters of the hexavalent actinide cation complexes. In contrast to DMAPA, TMPDA exhibits no observable complexation with the three hexavalent actinide cations in aqueous solution, which could be attributed to low electron density on the donor atoms of TMPDA as well as steric hindrance effect by dimethyl carbamoyl groups as elucidated by DFT calculations. The results from this work provide new insights into the complexation trends of hexavalent actinide cations in aqueous solutions.

更新日期：2019-08-22

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