Complexation and Solvent Extraction Properties of the N, N, N', N'-tetraethyl-1,10-phenanthroline-2,9-Diamide Extractant with Ln(III) and An(III)

Characterization of the coordination chemistry of the trivalent actinides (An(III)) with extractants is vital to the remediation of nuclear fuel cycle waste. The chemistry of the An(III), beyond Am(III) and Cm(III), in solvent extraction is not widely understood in terms of extraction behavior, but is essential to understanding separation schemes. Phenanthroline diamide (DAPhen) ligands have been of recent interest in the f-element separation field due to having molar acid stability, no third phase formation, a rigid backbone structure for faster complexation kinetics, tunable amide arms, and binding through both nitrogen and oxygen ((N,O)-donor) atoms. Investigating trends across the trivalent lanthanide (Ln(III)) and An(III) series can provide insight into the bonding and extraction trends with DAPhen ligands. A series of studies have been completed with the N, N, N', N'-tetraethyl-1,10-phenanthroline-2,9-diamide (TEtDAPhen) extractant to elucidate the bonding and extraction trends of the An(III) and Ln(III). Solvent extraction results have revealed higher affinity for An(III). The distribution ratios from Am(III)-Cf(III) have shown that Am(III) and Bk(III) have near identical extraction followed by Cf(III) and then Cm(III), resulting in an interesting trend. This decrease in Cm(III), Bk(III), and Cf(III) distribution ratios with respect to Am(III) has not been previously observed for the DAPhen systems. The figure below shows an example of a Ln(TEtDAPhen)(NO₃)₃ complex. Interesting trends in bonding across the Ln(III) series from Pr(III)-Lu(III) have been observed, in addition to comparison to Am(III). This allows for investigation of any differences in bonding between the An(III) and Ln(III). These results will be presented