Tamain Christelle, Dumas Thomas, Hennig Christoph, Guilbaud Philippe
CEA, Nuclear Energy Division, Research Department on Processes for Mining and Fuel Recycling, SPDS, LILA, CEA Marcoule, BP17171, 30207, Bagnols sur Cèze, France.
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstr. 400, 01328, Dresden, Germany.
Chemistry. 2017 May 17;23(28):6864-6875. doi: 10.1002/chem.201700493. Epub 2017 Apr 20.
Three tetravalent actinide (An ) hexanuclear clusters with the octahedral core [An (OH) O ] (An =U , Np , Pu ) were structurally characterized in the solid state and in aqueous solution by using single-crystal X-ray diffraction, X-ray absorption, IR, Raman, and UV/Vis spectroscopy. The observed structure, [An (OH) O (H O) (HDOTA) ]⋅HCl/HNO ⋅n H O (An=U(I), Np(II), Pu(III)), consists of a An hexanuclear pseudo-octahedral cluster stabilized by DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands. The six actinide atoms are connected through alternate μ -O and μ -OH groups. Extended X-ray absorption fine structure (EXAFS) investigations combined with UV/Vis spectroscopy provide evidence for the same local structure in moderate acidic and neutral aqueous solutions. The synthesis mechanism was partially elucidated and the main physicochemical properties (pH range stability, solubility, and protonation constant) of the cluster were determined. The results underline the importance of: 1) considering such polynuclear species in thermodynamic models, and 2) competing reactions between hydrolysis and complexation. It is interesting to note that the same synthesis route with thorium(IV) led to the formation of a dimer, Th (H O) (H DOTA) ⋅4 NO ⋅x H O (IV), which contrasts to the structure of the other An hexamers.
通过使用单晶X射线衍射、X射线吸收、红外、拉曼和紫外/可见光谱，对三种具有八面体核心[An₆(OH)₁₂O₆]（An = U、Np、Pu）的四价锕系元素（An）六核簇在固态和水溶液中的结构进行了表征。观察到的结构[An₆(OH)₁₂O₆(H₂O)₆(HDOTA)₂]⋅HCl/HNO₃⋅n H₂O（An = U(IV)、Np(IV)、Pu(IV)）由通过DOTA（1,4,7,10 - 四氮杂环十二烷 - 1,4,7,10 - 四乙酸）配体稳定的An六核伪八面体簇组成。六个锕系元素原子通过交替的μ₃ - O和μ₂ - OH基团相连。扩展X射线吸收精细结构（EXAFS）研究与紫外/可见光谱相结合，为中等酸性和中性水溶液中的相同局部结构提供了证据。部分阐明了合成机理，并测定了该簇的主要物理化学性质（pH范围稳定性、溶解度和质子化常数）。结果强调了以下几点的重要性：1）在热力学模型中考虑此类多核物种；2）水解和络合之间的竞争反应。有趣的是，钍（IV）的相同合成路线导致形成二聚体Th₂(H₂O)₈(H₂DOTA)₂⋅4 NO₃⋅x H₂O（IV），这与其他An六聚体的结构形成对比。
