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Title: Quantifying the binding strength of salicylaldoxime–uranyl complexes relative to competing salicylaldoxime–transition metal ion complexes in aqueous solution: a combined experimental and computational study

Abstract

Here, the design of new ligands and investigation of UO 2 2+ complexations are an essential aspect of reducing the cost of extracting uranium from seawater, improving the sorption efficiency for uranium and the selectivity for uranium over competing ions (such as the transition metal cations). The binding strengths of salicylaldoxime–UO 2 2+ complexes were quantified for the first time and compared with the binding strengths of salicylic acid–UO 2 2+ and representative amidoxime–UO 2 2+ complexes. We found that the binding strengths of salicylaldoxime–UO 2 2+ complexes are ~2–4 log β 2 units greater in magnitude than their corresponding salicylic acid–UO 2 2+ and representative amidoxime–UO 2 2+ complexes; moreover, the selectivity of salicylaldoxime towards the UO 2 2+ cation over competing Cu 2+ and Fe 3+ cations is far greater than those reported for salicylic acid and glutarimidedioxime in the literature. The higher UO 2 2+ selectivity can likely be attributed to the different coordination modes observed for salicylaldoxime–UO 2 2+ and salicylaldoxime–transition metal complexes. Density functional theory calculations indicate that salicylaldoxime can coordinate with UO 2 2+ as a dianion species formed by η 2 coordination of the aldoximate and monodentate binding of the phenolate group. Inmore » contrast, salicylaldoxime coordinates with transition metal cations as a monoanion species via a chelate formed between phenolate and the oxime N; the complexes are stabilized via hydrogen bonding interactions between the oxime OH group and phenolate. By coupling the experimentally determined thermodynamic constants and the results of theoretical computations, we are able to derive a number of ligand design principles to further improve the UO 2 2+ cation affinity, and thus further increase the selectivity of salicylaldoxime derivatives.« less

Authors:
 [1];  [2]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [2];  [4]; ORCiD logo [3]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Univ. of North Carolina, Wilmington, NC (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1462912
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Dalton Transactions
Additional Journal Information:
Journal Volume: 45; Journal Issue: 22; Journal ID: ISSN 1477-9226
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Mehio, Nada, Ivanov, Alexander S., Williams, Neil J., Mayes, Richard T., Bryantsev, Vyacheslav S., Hancock, Robert D., and Dai, Sheng. Quantifying the binding strength of salicylaldoxime–uranyl complexes relative to competing salicylaldoxime–transition metal ion complexes in aqueous solution: a combined experimental and computational study. United States: N. p., 2016. Web. doi:10.1039/c6dt00116e.
Mehio, Nada, Ivanov, Alexander S., Williams, Neil J., Mayes, Richard T., Bryantsev, Vyacheslav S., Hancock, Robert D., & Dai, Sheng. Quantifying the binding strength of salicylaldoxime–uranyl complexes relative to competing salicylaldoxime–transition metal ion complexes in aqueous solution: a combined experimental and computational study. United States. doi:10.1039/c6dt00116e.
Mehio, Nada, Ivanov, Alexander S., Williams, Neil J., Mayes, Richard T., Bryantsev, Vyacheslav S., Hancock, Robert D., and Dai, Sheng. Mon . "Quantifying the binding strength of salicylaldoxime–uranyl complexes relative to competing salicylaldoxime–transition metal ion complexes in aqueous solution: a combined experimental and computational study". United States. doi:10.1039/c6dt00116e. https://www.osti.gov/servlets/purl/1462912.
@article{osti_1462912,
title = {Quantifying the binding strength of salicylaldoxime–uranyl complexes relative to competing salicylaldoxime–transition metal ion complexes in aqueous solution: a combined experimental and computational study},
author = {Mehio, Nada and Ivanov, Alexander S. and Williams, Neil J. and Mayes, Richard T. and Bryantsev, Vyacheslav S. and Hancock, Robert D. and Dai, Sheng},
abstractNote = {Here, the design of new ligands and investigation of UO22+ complexations are an essential aspect of reducing the cost of extracting uranium from seawater, improving the sorption efficiency for uranium and the selectivity for uranium over competing ions (such as the transition metal cations). The binding strengths of salicylaldoxime–UO22+ complexes were quantified for the first time and compared with the binding strengths of salicylic acid–UO22+ and representative amidoxime–UO22+ complexes. We found that the binding strengths of salicylaldoxime–UO22+ complexes are ~2–4 log β2 units greater in magnitude than their corresponding salicylic acid–UO22+ and representative amidoxime–UO22+ complexes; moreover, the selectivity of salicylaldoxime towards the UO22+ cation over competing Cu2+ and Fe3+ cations is far greater than those reported for salicylic acid and glutarimidedioxime in the literature. The higher UO22+ selectivity can likely be attributed to the different coordination modes observed for salicylaldoxime–UO22+ and salicylaldoxime–transition metal complexes. Density functional theory calculations indicate that salicylaldoxime can coordinate with UO22+ as a dianion species formed by η2 coordination of the aldoximate and monodentate binding of the phenolate group. In contrast, salicylaldoxime coordinates with transition metal cations as a monoanion species via a chelate formed between phenolate and the oxime N; the complexes are stabilized via hydrogen bonding interactions between the oxime OH group and phenolate. By coupling the experimentally determined thermodynamic constants and the results of theoretical computations, we are able to derive a number of ligand design principles to further improve the UO22+ cation affinity, and thus further increase the selectivity of salicylaldoxime derivatives.},
doi = {10.1039/c6dt00116e},
journal = {Dalton Transactions},
number = 22,
volume = 45,
place = {United States},
year = {Mon Mar 07 00:00:00 EST 2016},
month = {Mon Mar 07 00:00:00 EST 2016}
}

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