A new uranyl benzoate species characterized by different spectroscopic techniques

Lütke, Laura; Moll, Henry; Bernhard, Gert

doi:10.1524/ract.2012.1916

Cited by 12 publications

(8 citation statements)

References 23 publications

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“…Hence, in the formation of URCP2 obtained at pH 2.62, all these three components are observed in the first coordination sphere of the uranyl center (Scheme b). With the increasing of solution pH values, deprotonated BA shows stronger coordination capability (log K ≈ 4.48) than CB[6] and prefers to form a 1:2 complex with uranyl ion . This means C7BPCA is easier to coordinate with UO 2 2+ and can produce steric hindrance to prevent CB[6] from participating in meta-organic coordination (Scheme c).…”

Section: Resultsmentioning

confidence: 99%

Uranyl Compounds Involving a Weakly Bonded Pseudorotaxane Linker: Combined Effect of pH and Competing Ligands on Uranyl Coordination and Speciation

Mei

et al. 2019

Inorg. Chem.

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Pseudorotaxane-type ligands with tunable structural dynamics offer an opportunity in the exploration of new actinide hybrid materials. In this work, we utilized a weakly bonded pseudorotaxane ligand involving CB[6] and 1, 1′-(heptane-1, 7-diyl)bis(4-(ethoxycarbonyl)pyridin-1-ium) bromides ([C7BPCEt]Br 2 @CB[6]) to assemble with uranyl ion, and we systematically investigated the effect of different factors including pH and competing ligands on the hydrothermal synthesis of URCPs. Nine uranyl-rotaxane coordination polymers (URCPs) with diversity in coordination mode and topological structure were successfully prepared (two previously reported complexes, URCP1 and URCP2 are also included). The results indicate that sulfate, bromide, CB[6], and C7BPCA (the hydrolyzate of [C7BPCEt]Br 2 ) show a combined influence on the obtained URCPs. At low pH, both CB[6] and C7BPCA can bond with uranyl centers and produce interwoven structures in URCP1, URCP2, and URCP6; at high pH, C7BPCA and competing anions (sulfate and bromide) have priority to coordinate with uranyl ions in URCP3–URCP5 and URCP7–URCP9. Notably, for the first time, bromide anion with lower affinity to uranyl ions is also observed in solid-state uranyl coordination polymer (URCP7–URCP9), which has been demonstrated by both energy dispersive X-ray spectroscopy and single-crystal X-ray structure analysis. In addition, a spontaneously single-crystal-to-single-crystal transformation from URCP3 to URCP4, which is driven by thermodynamics, was observed and explained by computational study. Moreover, it reveals that sulfate with stronger coordination ability can inhibit the hydrolysis of uranyl ion to some extent with only a rarely reported pentanuclear uranyl center found in URCP5 obtained at pH 5.67. These results indicate that the combined effect of competing ligands and pH has great significance in the formation of URCPs in terms of uranyl coordination and speciation and can be an alternative way to design and synthesize uranyl coordination polymers with new topologies.

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Section: Resultsmentioning

confidence: 99%

Uranyl Compounds Involving a Weakly Bonded Pseudorotaxane Linker: Combined Effect of pH and Competing Ligands on Uranyl Coordination and Speciation

Mei

et al. 2019

Inorg. Chem.

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“…TRLFS is a powerful technique especially useful for the determination of the uranium speciation at low, environmentally relevant concentrations. [21][22][23]…”

Section: Introductionmentioning

confidence: 99%

Insights into the uranium(vi) speciation with Pseudomonas fluorescens on a molecular level

2012

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Microorganisms have great potential to bind and thus transport actinides in the environment. Thus microbes indigenous to designated nuclear waste disposal sites have to be investigated regarding their interaction mechanisms with soluble actinyl ions when assessing the safety of a planned repository. This paper presents results on the pH-dependent sorption of U(VI) onto Pseudomonas fluorescens isolated from the granitic rock aquifers at Äspö Hard Rock Laboratory, Sweden. To characterize the U(VI) interaction on a molecular level, potentiometric titration in combination with time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied. This paper as a result is one of the very few sources which provide stability constants of U(VI) complexed by cell surface functional groups. In addition the bacteria-mediated liberation of inorganic phosphate in dependence on [U(VI)] at different pHs was studied to judge the influence of phosphate release on U(VI) mobilization. The results demonstrate that in the acidic pH range U(VI) is bound by the cells mainly via protonated phosphoryl and carboxylic sites. The complexation by carboxylic groups can be observed over a wide pH range up to around pH 7. At neutral pH fully deprotonated phosphoryl groups are mainly responsible for U(VI) binding. U(VI) can be bound by P. fluorescens with relatively high thermodynamic stability.

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“…The results of factor analysis were identical with those of the previous complexation study of uranyl monobenzoate, indicating that 1:1 complexation (uranyl to ligand) predominates and the higher stoichiometries can generally be excluded from the present uranyl complexations with the substituted benzoates. Regarding the higher stoichiometric complexations of uranyl ions with the benzoate moieties, a study reported solely on the formation of 1:2 uranyl benzoate under experimental conditions with an excess of ligand rather than U(VI) (concentration ratio >10) at pH 4–5, which differ considerably from those of the present aqueous solutions. In summary, a total of four reactions such as the protonation of substituted benzoates, two uranyl hydrolyses (UO 2 OH + , (UO 2 ) 2 (OH) 2 2+ ), and 1:1 complexation of uranyl with substituted benzoates were taken into account in the reaction model of nonlinear regression analysis of the UV–vis absorption data for each ligand.…”

Section: Resultsmentioning

confidence: 68%

“…Thus far, numerous studies have been performed to investigate the thermochemical features of aqueous U(VI) complexation with benzoate, which is the simplest aromatic monocarboxylate, by miscellaneous experimental methods. − With respect to the stoichiometry of the complexes, the formation of 1:1 complexation (uranyl to benzoate) was predominantly confirmed, whereas the formation of 1:1:1 ternary uranyl hydroxide benzoate and 1:2 complexes were exclusively observed at elevated temperatures and in solutions containing an excess of benzoic acid rather than U(VI), respectively. Moreover, the reaction enthalpy and entropy of 1:1 complexation and the ion interaction coefficient of uranyl monobenzoate with a perchlorate background anion were also determined.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Study on Aqueous Uranyl(VI) Complexes with Methoxy- and Methylbenzoates: Electronic and Steric Effects of the Substituents

Choi

Yun

2020

Inorg. Chem.

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Aqueous complexation of uranyl(VI) ions with methoxy- and methylbenzoates in 0.1 M NaClO4 solutions was studied by means of UV–vis absorption and Raman spectroscopy. The predominance of 1:1 complexation (uranyl to ligand) was verified for all uranyl carboxylates under acidic conditions (−log [H+] < 3.2), and absorption spectra, stability constants, and symmetric stretching frequencies of the uranyl group of the complexes were determined for the first time. For meta- and para-substituted benzoates, a linear free energy relationship (LFER) was observed between the equilibrium constants for the protonation (log βP) and uranyl complexation (log βU) reactions, and the electronic effects of the substituents were successfully described by the Hammett equation. In the case of ortho-substituted benzoates, the stability constant of uranyl 2-methoxybenzoate is slightly lower than the LFER trend, which is generally explained by the destabilization of cross-conjugation in the uranyl complex due to the steric hindrance between the reaction center and adjacent methoxy group. On the contrary, the stability constant of uranyl 2-methylbenzoate is comparable to the LFER trend, implying that the steric effect is relatively insignificant for the smaller methyl group. The utility of such thermodynamic correlations between the uranyl-substituted benzoates is useful for the molecular understanding and predictive modeling of chemical interactions between actinyl(VI) ions and various organic carboxyl groups.

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A new uranyl benzoate species characterized by different spectroscopic techniques

Cited by 12 publications

References 23 publications

Uranyl Compounds Involving a Weakly Bonded Pseudorotaxane Linker: Combined Effect of pH and Competing Ligands on Uranyl Coordination and Speciation

Uranyl Compounds Involving a Weakly Bonded Pseudorotaxane Linker: Combined Effect of pH and Competing Ligands on Uranyl Coordination and Speciation

Insights into the uranium(vi) speciation with Pseudomonas fluorescens on a molecular level

Spectroscopic Study on Aqueous Uranyl(VI) Complexes with Methoxy- and Methylbenzoates: Electronic and Steric Effects of the Substituents

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