锕酰冠醚配合物电子结构和化学成键理论研究进展

本文对锕系化合物的结构和性质的理论研究进行了规律性总结,并结合我们的研究成果,重点介绍了锕酰冠醚配合物的配位化学、电子结构和化学成键的基本特征。尽管近年来出现越来越多的光谱实验和晶体学数据报道,但是对锕系配合物的电子结构和化学成键的理论研究还不够系统。本文对锕酰冠醚配合物的配位结构、稳定能和光谱性质的计算结果进行了综述。大环配体(硫代)冠醚的腔体大小决定了配合物的结构特征。通过理论研究,在锕酰冠醚配合物中存在具有典型的An≡Oactinyl共价键和An-Oligand和An-Sligand离子键。对于离子键An-Oligand和An-Sligand,An和供电子配体之间通过价原子轨道的径向分布重叠形成微弱的共价相互作用。从U到Cm,配体向金属的电荷转移(LMCT)逐渐显著,导致Am和Cm的氧化态降低,金属离子与配体的作用变弱。这一成键规律和金属氧化态的变化规律,为实验上筛选合理且高效的镧锕分离配体提供重要理论指导。

Theoretical Studies on Electronic Structure and Chemical Bonding of Actinyl Crown Ether Complexes

In this mini-review, we have briefly summarized the theoretical research on geometrical structures and coordination chemistry of actinide complexes, the electronic structures of actinyl-crown-ether complexes, and the basic principle for chemical bonding of actinyl complexes. Although increasingly numerous spectroscopy and crystallography data had been available experimentally, there were lack of systematic investigations on theoretically electronic structure and chemical bonding of actinide complexes. Herein reviewed are our recently works from computational chemistry modeling on the coordination structures, stabilization energies and spectra properties of actinyl-crown-ether complexes. Our research has shown that the in-cavity complexes and their bonding features between(thio)-crown ethers and f-elements exhibit conventional conformations, with typical An≡Oactinyl and An-Oligand and An-Sligand distances. The typical ionic An-Oligand and An-Sligand bonds with an extent of covalent interaction between the An and ligand donor atoms primarily attributable to the overlap degree of radial distribution of valence atomic orbitals. From U to Cm, LMCT is gradually significant, resulting in the decrease of the formal oxidation state of Am and Cm, and the weakening of the interaction between metal ions and ligands. This periodicity of chemical bonding and the metal oxidation state provide fundamental guidance for the design of reasonable and efficient ligands in the application of lanthanide-actinide separation.