Complexation of uranium(vi) with glutarimidoxioxime: thermodynamic and computational studies

Abstract

The complex formation between a cyclic ligand glutarimidoxioxime (denoted as HL(III) in this paper) and UO2(2+) is studied by potentiometry and microcalorimetry. Glutarimidoxioxime (HL(III)), together with glutarimidedioxime (H2L(I)) and glutardiamidoxime (H2L(II)), belongs to a family of amidoxime derivatives with prospective applications as binding agents for the recovery of uranium from seawater. An optimized procedure of synthesis that leads to the preparation of glutarimidoxioxime in the absence of other amidoxime byproducts is described in this paper. Speciation models based on the thermodynamic results from this study indicate that, compared with H2L(I) and H2L(II), HL(III) forms a much weaker complex with UO2(2+), UO2(L(III))(+), and cannot effectively compete with the hydrolysis equilibria of UO2(2+) under neutral or alkaline conditions. DFT computations, taking into account the solvation by including discrete hydration water molecules and bulk solvent effects, were performed to evaluate the structures and energies of the possible isomers of UO2(L(III))(+). Differing from the tridentate or η(2)-coordination modes previously found in the U(vi) complexes with amidoxime-related ligands, a bidentate mode, involving the oxygen of the oxime group and the nitrogen of the imino group, is found to be the most probable mode in UO2(L(III))(+). The bidentate coordination mode seems to be stabilized by the formation of a hydrogen bond between the carbonyl group of HL(III) and a water molecule in the hydration sphere of UO2(2+).

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

“…For instance, polyacrylonitrile polymers are easily functionalized with amidoxime groups, which makes these types of materials of particular interest for extracting U(VI) from sea water. The coordination geometry of uranium adsorbed to amidoxime have been studied using extended x-ray absorption fine structure (EXAFS) [240], X-ray absorption near-edge structure (XANES) [241], density function theory (DFT) [242,243], as well as Raman and IR spectroscopy [242,244–246]. DFT studies suggested that uranyl coordinated with amidoxime groups form tridentate or η 2 – coordination structures [243].…”

para-Aminosalicylic acid in the treatment of manganese toxicity. Complexation of Mn2+ with 4-amino-2-hydroxybenzoic acid and its N-acetylated metabolite

“…This suggests that the logβ values reported in Table 2, which show that the formation of the Mn-L complexes is more favorable following the AcPAS > SAL > PAS order, could not primarily influenced by the strength of the Mn-L interaction. Evidently this difference in stability could be due to a delicate balance of metalligand interaction and solvation properties of the reagents and products as previously observed [55][56][57].…”

Gas‐phase complexes formed between amidoxime ligands and vanadium or iron investigated using electrospray ionization mass spectrometry

“…Several research groups have examined the complexation chemistry of uranium and transition metal cations that can compete for binding sites on the amidoxime sorbent with small ligands having amidoxime functional groups in an effort to develop a more complete understanding of metal binding to the amidoxime‐functionalized sorbents . The amidoxime ligands are often modeled using cyclic 2,6‐dihydroxyiminopiperidine (DHIP) and acyclic N 1 , N 5 ‐ dihydroxypentanediimidamide (DHPD) (Fig.…”

“…The amidoxime ligands are often modeled using cyclic 2,6‐dihydroxyiminopiperidine (DHIP) and acyclic N 1 , N 5 ‐ dihydroxypentanediimidamide (DHPD) (Fig. ) . A third potential complexing group present in the sorbent has been modeled using glutarimidoxioxime …”