Influence of a Pre-organized N-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by an Aminopolycarboxylate Complexant

CR Heathman and TS Grimes and S Jansone-Popova and S Roy and VS Bryantsev and PR Zalupski, CHEMISTRY-A EUROPEAN JOURNAL, 25, 2545-2555 (2019).

DOI: 10.1002/chem.201804723

The thermodynamic influence of a pre-organized N-donor group on the coordination of trivalent actinides and lanthanides by an aqueous aminopolycarboxylate complexant has been investigated. The synthesized reagent, N-2-methylpicolinate-ethylenediamine-N,N',N'-triacetic acid (EDTA-Mpic), resembles ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) with a single acetate pendant arm replaced by a 6-carboxypyridin-2-ylmethyl group. The rigid N-donor picolinate functionality has a profound impact on ligand protonation and trivalent f element complexation equilibria, as demonstrated by potentiometric, spectroscopic, and liquid/liquid metal-partitioning studies as well as by molecular dynamics calculations. Relative to diethylenetriamine-N,N,N',N",N"-pentaacetic acid (DTPA), the ability to preferentially bind trivalent actinides over trivalent lanthanides was moderately lowered due to the presence of the N-(6-carboxypyridin-2-ylmethyl) substituent. The structural modification substantially amplifies the total ligand acidity of EDTA-Mpic. As a result the complexant sustains the metal complexation and efficient An(3+)/Ln(3+) differentiation in aqueous mixtures of unprecedented acidity for this class of reagents.

Return to Publications page