Zhang Peng, Wang Ya-Xing, Zhang Ping, Wang Shu-Ao, Hu Shu-Xian
Beijing Computational Science Research Center, Beijing 100193, China.
State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
Inorg Chem. 2020 Sep 8;59(17):11953-11961. doi: 10.1021/acs.inorgchem.0c00535. Epub 2020 Aug 7.
The separation and management of nuclear waste is one of the problems that needs to be solved urgently, so finding a new radiation-proof and durable extractant to deal with nuclear waste is a difficult but desirable task. Since the successful isolation of the first pentavalent plutonium crown ether complex recently (Wang et al. , , 425-431), complexes with actinyl(V/VI) inserted into the cavity of 18-crown-6 ether (oxo-18C6), as well as their bonding character, need to be explored. Here we present a series of novel crown ether complexes containing actinyl(V/VI) and oxo-18C6 via computational prediction and analysis. On the basis of the calculations, actinyl(V/VI) are thermodynamically feasible and can be stabilized by oxo-18C6 ligand via six dative bonds between An ions and the oxo-18C6 O atoms in the "insertion" structure of [AnO(18C6)] complexes. The stability of actinyl(VI) species generally falls at minor actinides, ascribed to the reduced highest possible oxidation states of curium, which is mainly attributed to the mixing of bonding orbitals and non-bonding orbitals as well as the increase of occupation on partially 5f antibonding orbitals. It is found that the interactions between the actinyl(V/VI) and oxo-18C6 are mainly electronic interactions, with the well-known covalency contributions generally decreasing from uranium to curium due to energy degeneracy and spatial orbital contraction. This work would give a basic understanding of the coordination chemistry of actinyl(V/VI), which also provides inspirations on the design of new extractants for actinide separations.
核废料的分离与管理是亟待解决的问题之一，因此寻找一种新型的防辐射且耐用的萃取剂来处理核废料是一项艰巨但令人期待的任务。自从最近首次成功分离出五价钚冠醚配合物（Wang等人，[参考文献]，425 - 431）以来，需要探索将锕酰（V/VI）插入18 - 冠 - 6醚（氧代 - 18C6）空腔形成的配合物及其键合特性。在此，我们通过计算预测和分析，展示了一系列含有锕酰（V/VI）和氧代 - 18C6的新型冠醚配合物。基于计算结果，锕酰（V/VI）在热力学上是可行的，并且在[AnO(18C6)]配合物的“插入”结构中，锕离子与氧代 - 18C6的O原子之间通过六个配位键，锕酰（V/VI）可被氧代 - 18C6配体稳定。锕酰（VI）物种在次锕系元素中的稳定性通常较低，这归因于锔的最高可能氧化态降低，这主要是由于成键轨道和非键轨道的混合以及部分5f反键轨道上占据数的增加。研究发现，锕酰（V/VI）与氧代 - 18C6之间的相互作用主要是电子相互作用，由于能量简并和空间轨道收缩，从铀到锔，众所周知的共价贡献通常逐渐降低。这项工作将对锕酰（V/VI）的配位化学有一个基本的认识，这也为锕系元素分离新型萃取剂的设计提供了灵感。
