How Amidoximate Binds the Uranyl Cation

Abstract

This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO(2)(2+). Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO(2)(AO)(x)(OH(2))(y)](2-x) (x = 1-3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η(2) binding with the N-O bond. The theoretical results establish the η(2) motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO(2)(2+) complexes with acetamidoxime and benzamidoxime anions.

Recovery of uranyl from aqueous solutions using amidoximated polyacrylonitrile/exfoliated Na-montmorillonite composite

“…Generally, 1:1, 1:2, 1:3 and 1:4 binding motifs of uranyl with amidoxime shown in Scheme 3 were proposed or observed in the literatures [29,38,39]. For convenience, the five binding motifs are labeled as M1, M2, M3, M4 and M5 respectively.…”

Recovery of Uranium from Seawater: Preparation and Development of Polymer-Supported Extractants

“…1). 7 Consideration of the hard-soft aspect of the exchange is also consistent with the absence of significant activity by the secondary and tertiary amines: increasing the organophilicity at the nitrogen increases the softness of the ammonium ligand 8 and thus decreases their affinity for the hard carbonate complex.…”

“…However, the efficiency of amidoximes decreases with sorption-elution cycles for reasons related to the stability of the chemical structures involved but not yet fully understood. 5,7 Moreover, amidoxime synthesis involves multistep processes, thus increasing the total cost of the final extraction.…”

Extraction of uranium from seawater : design and testing of a symbiotic system

“…In the third, 2-1c, the metal ion is bound with the N -O bond of oximido. UO 2 2+ has been founded to be almost exclusively observed to bind in the third (Vukovic et al, 2012;Kelley et al, 2014). Furthermore, extremely fast kinetics in the uptake of other metal ions by the amidoxime adsorbent suggests that the major cations are not binding solely to amidoxime ligands, but rather primarily to nonspecific sites (e.g., COO -) on the adsorbent, possibly due to their very high concentration in seawater .…”