Complexation of trivalent Eu and Am ions with phenanthroline-derived ligands tuned by rotating thiazole/oxazole substituents

The reprocessing of spent nuclear fuels is greatly challenging, as the current separation technique of lanthanide (Ln) and actinide (An) suffers too many difficulties. In this paper, selective ligands of phenanthroline derivatives modified by thiazole/oxazole were designed by relativistic density functional theory calculations. Their complexation of Eu3+ and Am3+ and the mechanism of selective separation were comprehensively examined. The spatial rotation against the CC bond between phenanthroline and thiazole/oxazole has access to six ligands. It is shown that Looo with oxazole substituents and their oxygens being opposite is the best electron donor for metal ions. The results of WBIs and MBO unravel that Am-L bond has more covalency than respective Eu-L bond. From topological analyses, it is found that these metal–ligand bonds are dominated by electrostatic interaction and largely of ionic bond character. Thermodynamically, all ligands prefer binding Eu3+ to Am3+.