Bicyclic and Acyclic Diamides:  Comparison of Their Aqueous Phase Binding Constants with Nd(III), Am(III), Pu(IV), Np(V), Pu(VI), and U(VI)

Abstract

This report describes affinity measurements for two, water-soluble, methyl-alkylated diamides incorporating the malonamide functionality, N,N,N',N' tetramethylmalonamide (TMMA) and a bicyclic diamide (1a), toward actinide metal cations (An) in acidic nitrate solutions. Ligand complexation to actinides possessing oxidation states ranging from +3 to +6 was monitored through optical absorbance spectroscopy, and formation constants were obtained from the refinement of the spectrophotometric titration data sets. Species analysis gives evidence for the formation of 1, 4, 1, and 2 spectrophotometrically observable complexes by TMMA to An(III, IV, V, and VI), respectively, while for 1a, the respective numbers are 3, 4, 2, and 2. Consistent with the preorganization of 1a toward actinide binding, a significant difference is found in the magnitudes of their respective formation constants at each complexation step. It has been found that the binding affinity for TMMA follows the well-established order An(V) < An(III) < An(VI) < An(IV). However, with 1a, Np(V) forms stronger complexes than Am(III). The complexation of 1a with Np(V) and Pu(VI) at an acidity of 1.0 M is followed by reduction to Np(IV) and Pu(IV), whereas TMMA does not perturb the initial oxidation state for these dioxocations. These measurements of diamide binding affinity mark the first time single-component optical absorbance spectra have been reported for a span of actinide-diamide complexes covering all common oxidation states in aqueous solution.

Malonamide-Functionalized Gold Nanoparticles for Selective, Colorimetric Sensing of Trivalent Lanthanide Ions

“…Studies have shown malonamides to display different binding affinities for different lanthanide ions. 64 Introducing a lower malonamide density on the nanoparticles through incorporation of a mixed ligand shell on the particle surface may facilitate lanthanide selectivity and result in a distinct plasmon signature for each individual ion, as has been shown in the literature for several toxic heavy metal ions. 24 The temporal response of the sensor was measured by monitoring a region of the absorbance spectra corresponding to bicyclic malonamide.…”

Studies on the Uptake and Column Chromatographic Separation of Eu, Th, U, and Am by Tetramethylmalonamide Resin

“…This order was the same as that of the stability constants for these metal-ion TMMA complexes in HNO 3 solution. [11] In NaNO 3 media, the K d values of all of the metal ions increased with increasing [NaNO 3 ], except for the K d of Th(IV) in 7 M NaNO 3 . Because TMMA is a neutral ligand, the metal ions must be neutralized by counter-anions that are extracted onto the resin.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13] Although the chemical components and radioactivity of LLW differ from those of HLW, the selectivity and extraction ability of malonamide derivatives suggested their applicability in the analysis of An in solutions of digested LLWs. Recently, malonamide derivatives have been covalently bonded to a polymer to produce a solid extraction resin for column chromatography.…”

Design and synthesis of chelating diamide sorbents for the separation of lanthanides

“…Chelating diamides have been recognized for a number of years as being affective ligands for solvent extraction of lanthanides and actinides [41][42][43][44][45][46][47][48][49]. Tetraalkyl malonamides and succinamides have been studied in [42,43,[45][46][47].…”

“…This work was subsequently followed up by work aimed at synthesizing chelating diamide ligands specifically designed for rare earth chelation by controlling the dihedral angle between the two carbonyl groups through the use of a rigid backbone [44]. Ultimately, this led to the development of rigid bicyclic diamides, tailored for the solvent extraction of rare earth cations [41,48,49]. This precedent demonstrates that an aprotic chelating diamide ligand should have good affinity for lanthanide cations.…”