The Complex Chemistry of the Uranyl Ion. VII. The Complexity of Uranyl Glycolate.

Ahrland, Sten; Grahn, Margareta; Fex, H.; Högberg, B.; Linderot, T.; Rosenberg, Th.

doi:10.3891/acta.chem.scand.07-0485

Cited by 25 publications

(13 citation statements)

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“…This is with the exception of l -glycine, which uses eq , in line with experimental derivation Experimental and calculated stability constants are presented in Table . ,,− The calculated versus experimental log β values presented in Figure show a linear trend with a correlation coefficient ( R 2 ) of 0.911, similar to the correlation found by ref ( R 2 = 0.926). Equation has been obtained from the data plotted in Figure and is used to fit the calculated log β of 1:1 U VI complexes.…”

Section: Results and Discussionsupporting

confidence: 78%

Computational Tools for Calculating log β Values of Geochemically Relevant Uranium Organometallic Complexes

et al. 2018

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Uranium (U) interacts with organic ligands, subsequently controlling its aqueous chemistry. It is therefore imperative to assess the binding ability of natural organic molecules. We evidence that density functional theory (DFT) can be used as a practical protocol for predicting the stability of U organic ligand complexes, allowing for the development of a relative stability series for organic complexes with limited experimental data. Solvation methods and DFT settings were benchmarked to suggest a suitable off-the-shelf solution. The results indicate that the IEFPCM solvation method should be employed. A mixed solvation approach improves the accuracy of the calculated stability constant (log β); however, the calculated log β are approximately five times more favorable than experimental data. Different basis sets, functionals, and effective core potentials were tested to check that there were no major changes in molecular geometries and Δ G. The recommended method employed is the B3LYP functional, aug-cc-pVDZ basis set for ligands, MDF60 ECP and basis set for U, and the IEFPCM solvation model. Using the fitting approach employed in the literature with these updated DFT settings allows fitting of 1:1 U complexes with root-mean-square deviation of 1.38 log β units. Fitting multiple bound carboxylate ligands indicates a second, separate fitting for 1:2 and 1:3 complexes.

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Section: Results and Discussionsupporting

confidence: 78%

Computational Tools for Calculating log β Values of Geochemically Relevant Uranium Organometallic Complexes

et al. 2018

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“…The complexation of U VI with catecholate, α-hydroxycarboxylate, hydroxamate and α-aminocarboxylate have been explored using experimental techniques including potentiometry, spectrophotometry, time-resolved laser fluorescence spectroscopy (TRLFS), nuclear magnetic resonance spectrometry (NMR), and extended X-ray absorption fine structure (EXAFS). − Catecholate, hydroxamate, and α-aminocarboxylate have been explored computationally using density functional theory (DFT). ,,− However, structural and stability data have not been determined for the α-hydroxyimidazolate and hydroxy-phenyloxazolonate functional groups, leaving an incomplete understanding of their possible importance in the formation of siderophore complexes with uranyl.…”

Section: Introductionmentioning

confidence: 99%

Stability Series for the Complexation of Six Key Siderophore Functional Groups with Uranyl Using Density Functional Theory

et al. 2020

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Determining stability constants of uranyl complexes with the principal functional groups in siderophores and identifying stability series is of great importance to predict which siderophore classes preferentially bind to U VI and, hence, impact uranium speciation in the environment. It also helps to develop resins for scavenging U VI from aqueous solutions. Here, we apply a recently developed computational approach to calculate log β values for a set of geochemically relevant uranium organometallic complexes using Density Functional Theory (DFT). We determined the stability series for catecholate, hydroxamate, α-hydroxycarboxylate, α-aminocarboxylate, hydroxy-phenyloxazolonate, and α-hydroxyimidazole with the uranyl cation. In this work, the stability constants (log β 110 ) of α-hydroxyimidazolate and hydroxy-phenyloxazolonate are calculated for the first time. Our approach employed the B3LYP density functional approximation, aug-cc-pVDZ basis set for ligand atoms, MDF60 ECP for U VI , and the IEFPCM solvation model. DFT calculated log β 110 were corrected using a previously established fitting equation. We find that the siderophore functional groups stability decreases in the order: α-hydroxycarboxylate bound via the α-hydroxy and carboxylate groups (log β 110 = 17.08), α-hydroxyimidazolate (log β 110 = 16.55), catecholate (log β 110 = 16.43), hydroxamate (log β 110 = 9.00), hydroxy-phenyloxazolonate (log β 110 = 8.43), α-hydroxycarboxylate bound via the carboxylate group (log β 110 = 7.51) and α-aminocarboxylate (log β 110 = 4.73). We confirm that the stability for the binding mode of the functional groups decrease in the order: bidentate, monodentate via ligand O atoms, and monodentate via ligand N atoms. The stability series strongly suggests that α-hydroxyimidazolate is an important functional group that needs to be included when assessing uranyl mobility and removal from aqueous solutions.

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“…They also find extensive application in separation processes of various types, e.g., group and element separations of 4 f and 5 f elements. Quantitative studies of their complex formation reactions have been made in the pH range 3 to 5 mainly using potentiometry and NMR techniques [1][2][3][4][5]. The first study of the complex formation of uranium(VI) with glycolate was made using potentiometry by Ahrland [1] who identified the species MA, MA 2 , and MA 3 , where A is HOCH 2 COO − and M is UO 2 2+ .…”

Section: Introductionmentioning

confidence: 99%

“…Quantitative studies of their complex formation reactions have been made in the pH range 3 to 5 mainly using potentiometry and NMR techniques [1][2][3][4][5]. The first study of the complex formation of uranium(VI) with glycolate was made using potentiometry by Ahrland [1] who identified the species MA, MA 2 , and MA 3 , where A is HOCH 2 COO − and M is UO 2 2+ . Magon et al [2] investigated the complex formation of actinyl ions (UO 2 2+ , NpO 2 2+ , PuO 2 2+ ) with α-, β-, and γ -hydroxymonocarboxylate ligands by potentiometry and identified the same type of complexes.…”

Section: Introductionmentioning

confidence: 99%

Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

Moll¹,

Geipel²,

Reich³

et al. 2003

Radiochimica Acta

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The complex formation in the binary uranium(VI)-glycolate, -α-hydoxyisobutyrate, -α-aminoisobutyrate systems in 1.0 M NaClO 4 medium was studied by means of UV-vis, TRLFS, and EXAFS. An increase in absorption and a red shift of the spectra, 5 nm compared to the free UO 2 2+ , indicate a complex formation between UO 2 2+ and α-substituted carboxylic acids already at pH 2. 1 : 1 complexes dominate the uranyl speciation in the glycolate, α-hydoxyisobutyrate, and α-aminoisobutyrate system at pH 2 and 3, respectively. At higher ligand concentrations a 1 : 2 complex between UO 2 2+ and α-aminoisobutyric acid was observed.There is a very strong quenching of the U(VI) fluorescence in the uranyl-α-hydroxycarboxylate systems that can be quantitatively described by the Stern-Volmer equation. As a result of the strong quenching it is not possible to detect fluorescence spectra for these complexes using TRLFS. The UO 2 2+ (aq) concentration calculated from the Stern-Volmer equation was used to determine equilibrium constants which are in good agreement with those obtained by potentiometry and NMR spectroscopy. No quenching was observed in the α-aminoisobutyrate system and their fluorescence spectra could be deconvoluted into components for the different species present. The following stability constants result from our TRLFS experiments: a) for the glycolate system log β UO 2 (HOCH 2 COO) + = 2.52 ± 0.20, b) for the α-hydroxyisobutyrate system log β UO 2 [HOC(CH 3 ) 2 COO] + = 3.40 ± 0.21, and c) for the α-aminoisobutyrate system log β UO 2 [NH 3 C(CH 3 ) 2 COO] 2+ = 1.30 ± 0.10 and log β UO 2 [NH 3 C(CH 3 ) 2 COO] 2 2+ = 2.07 ± 0.25. An increase of the fluorescence intensity connected with a red shift of the fluorescence emission spectra was observed in the system uranyl-α-aminoisobutyric acid. Fluorescence lifetimes and spectra were obtained for UO 2 2+ , UO 2 [NH 3 C(CH 3 ) 2 COO] 2+ , and UO 2 [NH 3 C(CH 3 ) 2 COO] 2 2+ . Uranium L III -edge EXAFS measurements yielded an U−O eq distance of 2.40 to 2.43 Å in the pH range from 2 to 4 in the α-hydroxyisobutyrate system showing a dominant bidentate coordination via the oxygens of the carboxylic group. Slightly shorter U−O eq distances of 2.40 to 2.38 Å and no evidence for U−C distances around 2.90 Å in the glycolate system in this pH range may indicate a monodentate coordinated ligand via one oxygen from the carboxylic group. The decrease in the U−O eq distance of the equatorial oxygens in both systems to pH values ≥ 5 is a strong indication for the formation of a chelate complex due to the deprotonation of the α-OH-group of the ligand. In the glycolate system in the pH range 5.5 to 11, the EXAFS spectrum showed evidence of U−U interaction at 3.81 Å indicating the formation of dimeric species.

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The Complex Chemistry of the Uranyl Ion. VII. The Complexity of Uranyl Glycolate.

Cited by 25 publications

References 0 publications

Computational Tools for Calculating log β Values of Geochemically Relevant Uranium Organometallic Complexes

Computational Tools for Calculating log β Values of Geochemically Relevant Uranium Organometallic Complexes

Stability Series for the Complexation of Six Key Siderophore Functional Groups with Uranyl Using Density Functional Theory

Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

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