2-Methylpyrrolidine derived 1,10-phenanthroline-2,9-diamides: promising extractants for Am(iii)/Ln(iii) separation

In this work we report on new examples of phenanthrolindiamides containing asymmetric centers in amide substituents. The synthesized ligands are expected to have complex thermodynamic behavior. Their structure was unambiguously confirmed by a combination of spectral analysis methods and X-ray analysis. It is shown that the obtained ligands form complexes with nitrates of rare-earth elements, and the stability constants of such complexes in acetonitrile solution were also measured. The performed solvent extraction tests revealed a significant effect of methyl groups in cyclic amide substituents on the distribution ratios and selectivity factors in the lanthanides(iii) and Am(iii) series in comparison with the previously studied ligands based on unsubstituted pyrrolidine. The observed effects are explained from the standpoint of quantum chemistry calculations taking into account possible stereoisomerism.