Gao Yang, Jennifer G Abigail, Varathan Elumalai, Schreckenbach Georg
Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China.
National Health Commission Key Laboratory of Nuclear Technology Medical Transformation, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang 621000, China.
Inorg Chem. 2023 Feb 20;62(7):3229-3237. doi: 10.1021/acs.inorgchem.2c04235. Epub 2023 Feb 6.
The minor actinides Am/Cm show multiple possibilities for coordination, providing great opportunities for their extraction and adsorption separation. Herein, we report complexation in an aqueous medium of Am/Cm in the DOTA (HDOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) cavity with axial ligands (OH, F, and HO), based on the energetics and electronic structure properties using density functional theory (DFT). The formation and substitution reactions of OH-capped complexes are more likely to occur due to their enhanced hydration Gibbs free energies, followed by F, and then HO. Both the longer An-O bond lengths and the larger bite angle (∠O-An-O) in the OH-capped complexes reflect the enhanced coordination provided by the axial ligand, slightly less so for F. Energy decomposition analysis based on the electronic structure supports the preference for OH-capped complexes with a near-perfect balance between attractive and repulsive contributions toward the interaction. Furthermore, molecular orbital analysis revealed that the frontier molecular orbitals of Am and Cm complexes are substantially different; that is, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) compositions of the Am complexes are all contributed by 5f, while the HOMO and LUMO compositions of the Cm complexes are derived from 5f and 6d, respectively. Finally, the metal-exchange reactions demonstrate competitive complexation of DOTA toward Am over Cm for the OH-capped system. These results imply the importance of coordination chemistry in actinide chemistry in general and specifically in Am/Cm solution chemistry.
次锕系元素镅/锔显示出多种配位可能性，为其萃取和吸附分离提供了巨大机遇。在此，我们基于密度泛函理论（DFT）的能量学和电子结构性质，报道了在DOTA（HDOTA = 1,4,7,10 - 四氮杂环十二烷 - 1,4,7,10 - 四乙酸）空腔中镅/锔与轴向配体（OH、F和HO）在水介质中的络合情况。由于其增强的水合吉布斯自由能，OH封端络合物的形成和取代反应更易发生，其次是F，然后是HO。OH封端络合物中较长的An - O键长和较大的咬角（∠O - An - O）都反映了轴向配体提供的增强配位，F的情况稍弱。基于电子结构的能量分解分析支持了对OH封端络合物的偏好，其对相互作用的吸引和排斥贡献之间近乎完美平衡。此外，分子轨道分析表明镅和锔络合物的前沿分子轨道有很大不同；也就是说，镅络合物的最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）组成均由5f贡献，而锔络合物的HOMO和LUMO组成分别来自5f和6d。最后，金属交换反应表明在OH封端体系中，DOTA对镅的络合竞争能力强于锔。这些结果表明配位化学在一般锕系元素化学中，特别是在镅/锔溶液化学中的重要性。
