Wang Shuai, Wang Cui, Yang Xiao-Fan, Yu Ji-Pan, Tao Wu-Qing, Yang Su-Liang, Ren Peng, Yuan Li-Yong, Chai Zhi-Fang, Shi Wei-Qun
Radiochemistry Laboratory, School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, P.R. China.
Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P.R. China.
Inorg Chem. 2021 Dec 20;60(24):19110-19119. doi: 10.1021/acs.inorgchem.1c02916. Epub 2021 Dec 3.
Although 1,10-phenanthroline-based ligands have recently shown vast opportunities for the separation of trivalent actinides (Ans(III)) from lanthanides (Lns(III)), the optimization and design of the extractant structure based on the phenanthroline framework remain hotspots for further improving the separation. Following the strategy of hard and soft donor atom combination, for the first time, the quinoline group was attached to the 1,10-phenanthroline skeleton, giving a lipophilic ligand, 2,9-diacyl-bis((3,4-dihydroquinoline-1((2H)-yl)-1),10-phenanthroline (QL-DAPhen)), for Am(III)/Eu(III) separation. In the presence of sodium nitrate, the ligand can effectively extract Am(III) over Eu(III) in HNO solution, with the separation factor () ranging from 29 to 44. The coordination chemistry of Eu(III) with QL-DAPhen was investigated by slope analysis, NMR titration, UV-vis titration, Fourier transform infrared spectroscopy, electrospray ionization-mass spectrometry, and theoretical calculations. The experimental results unanimously confirm that the ligand forms both 1:1 and 1:2 complexes with Eu(III), and the stability constants (log ) of each of the two complexes were obtained. Density functional theory calculations show that the Am-N bonds have more covalent characteristics than the Eu-N bonds in the complexes, which reveals the reason why the ligand preferentially bonds with Am(III). Meanwhile, the thermodynamic analysis reveals that the 1:1 complex is more thermodynamically stable than the 1:2 complex. The findings of this work have laid a solid theoretical foundation for the application of phenanthroline-based ligands in the separation of An(III) from practical systems.
尽管基于1,10 - 菲咯啉的配体最近在从镧系元素（Ln(III)）中分离三价锕系元素（An(III)）方面展现出巨大潜力，但基于菲咯啉框架的萃取剂结构优化与设计仍是进一步提升分离效果的研究热点。遵循硬软给体原子组合策略，首次将喹啉基团连接到1,10 - 菲咯啉骨架上，得到一种亲脂性配体2,9 - 二酰基 - 双((3,4 - 二氢喹啉 - 1((2H)-基)-1),10 - 菲咯啉（QL - DAPhen），用于分离Am(III)/Eu(III)。在硝酸钠存在下，该配体在硝酸溶液中能有效萃取Am(III)而不是Eu(III)，分离因子（β）范围为29至44。通过斜率分析、核磁共振滴定、紫外 - 可见滴定、傅里叶变换红外光谱、电喷雾电离 - 质谱以及理论计算等方法研究了Eu(III)与QL - DAPhen的配位化学。实验结果一致证实该配体与Eu(III)形成1:1和1:2两种配合物，并得到了这两种配合物各自的稳定常数（logβ）。密度泛函理论计算表明，配合物中Am - N键比Eu - N键具有更多共价特征，这揭示了该配体优先与Am(III)结合的原因。同时，热力学分析表明1:1配合物比1:2配合物在热力学上更稳定。本工作所得结果为基于菲咯啉的配体在从实际体系中分离An(III)的应用奠定了坚实的理论基础。
