Theoretical study of the ability of symmetric and asymmetric N-donor ligands to separate Am(III) and Eu(III) and the bonding nature

Separation properties of asymmetric N-donor ligands with Am(III)/Eu(III) complexes have been investigated by DFT methods. [Display omitted] •Chosen the theoretical method of PBE0/6-311 g*&RECP to Carry out full-text calculation.•Using Visual Molecular Dynamics software package to visualise the interaction between complexes, especially the natural bond orbital.•Comparing the thermodynamic properties of different reactions, the choice of solvent is crucial.•The f orbital occupies the major contribution in metal–ligand bonds.•Ligands with o-phenanthroline backbone have excellent extraction properties, and ligands with asymmetric side chains have good separation effects. In the reprocessing of spent nuclear fuel, nitrogen-donor extractants are more effective in separating actinides and lanthanides. In this article, a series of heterocyclic N-donor ligands with different backbones and different side chain substituents are systematically investigated to analyze their extraction selectivity and complexation abilities for Am(Ⅲ) and Eu(Ⅲ) by using scalar relativistic density functional theory (DFT). Through the analysis of geometric structures and bond properties of the complexes by means of the NBO and QTAIM methods, it was observed that the coordination ability of the N-donor ligand with Am(Ⅲ) was stronger than with Eu(Ⅲ). Thermodynamic analysis showed that these ligands have good extraction ability and separation performance for Am(III) and Eu(III), the backbone and side chain substituents of the ligands and also the organic solvents have significant influences on the extraction selectivity of the ligands for Am(III) and Eu(III) ions. This work provides some theoretical insights for the design of N-donor extractants with good separation performance for lanthanides and actinides.