Computational investigation of the speciation of uranyl gluconate complexes in aqueous solution

Abstract

The geometries, relative energies and spectroscopic properties of a range of D-gluconate complexes of uranyl(VI) are studied computationally using density functional theory. The effect of pH is accommodated by varying the number of water and hydroxide ligands accompanying gluconate in the equatorial plane of the uranyl unit. For 1 : 1 complexes, the calculated uranyl ν(asym) stretching frequency decreases as pH increases, in agreement with previous experimental data. Three different gluconate chelating modes are studied. Their relative energies are found to be pH dependent, although the energetic differences between them are not sufficient to exclude the possibility of multiple speciation. (13)C NMR chemical shifts are calculated for the coordinated gluconate in the high pH mimics, and show good agreement with experimental data, supporting the experimental conclusion that the six-membered chelate ring is favoured at high pH. Attempts to improve the description of the aqueous environment via the addition of second solvation shell water molecules resulted in significantly worse agreement with experiment for ν(asym). The effect of increasing the gluconate concentration is modelled by calculating 1 : 2 and 1 : 3 uranyl : D-gluconate complexes.

Is gluconate a good model for isosaccharinate in uranyl(vi) chemistry? A DFT study

“…In our previous work, 14 benchmark NMR calculations were performed on the uranyl Glu complexes, using a variety of different codes, functionals, and solvation effects. For consistency, the same parameters were used for the present uranyl Isa NMR calculations, i.e.…”

“…We recently reported the results of a computational study of the complexation of D-gluconate with U(VI) (in the form of uranyl UO 2 2+ ) in which we probed the effect of pH on the structures, relative energetics and spectroscopic properties of a range of uranyl/H 2 O/OH − /D-gluconate species. 14 The linear uranyl [OvUvO] 2+ unit is a hard ion and tends to form bonds with oxygen-containing ligands in its equatorial plane. [15][16][17][18][19][20] In the case of D-gluconate and α-isosaccharinate, it is known that the carboxylate group takes part in complexation and, in our uranylgluconate study, we studied complexes in which one or more gluconate ligands binds to the uranyl via carboxylate complexation in the equatorial plane, the remaining coordination sites being occupied by H 2 O, and/or hydroxide ligands or gluconate alcohol groups.…”

Molecular dynamics simulation of the interaction of uranium (VI) with the C–S–H phase of cement in the presence of gluconate

“…Uranyl can form complexes with more than one gluconate anion under alkaline conditions (Birjkumar et al, 2011;Colàs et al, 2013). The cation will mostly coordinate with deprotonated carboxyl groups of organic ion, but at highly alkaline solutions (pH > 13.9) the gluconate hydroxyl groups can be deprotonated and can also participate To summarize, the combination of the results for U(VI) in solution with the available literature data allows us to suggest that complex formation between uranyl hydroxides and Ca 2+ cations present at aqueous C-S-H interfaces should play a significant role in the sorption process.…”

Solvation effect and binding of rhaponticin with iron: a spectroscopic and DFT/TDDFT study

“…9 Geometry optimization in the ground state was carried out using B3LYP density functional calculations, with the DZP basis sets. 10 The lowest singlet excited-states of both the isolated RH and the hydrogen-bonded RH were calculated using time-dependent density functional theory (TD-DFT) with B3LYP hybrid functional and the TZVP basis set. 11…”