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Oxocomplexes of U(VI) with 8-Hydroxyquinoline-5-Sulfonate in Solution: Structural Studies and Photophysical Behaviour

Abstract

Multinuclear (1H and 13C) NMR, and Raman spectroscopy, combined with DFT calculations, provide detailed information on the complexation between the U(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, U(VI) oxoions (uranyl ions) form one dominant complex with 8-HQS in water in the pH range 3-6, a mononuclear 1:2 (metal:ligand) complex, with the metal centre (UO22+) coordinated to two 8-HQS ligands, together with one or more water molecules. An additional minor, 1:1 complex, has also been detected for solutions with 1:1 metal:ligand molar ratio. A geometry of the dominant complex is proposed based on the combination of NMR and Raman results with DFT calculations. Further information on the electronic structure of the complex has been obtained from UV/visible absorption and luminescence spectra. The complex between U(VI) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states below the emitting ligand-based and uranyl based levels which quench their emission. These studies have fundamental importance and are also relevant in the context of environmental studies, and the water soluble ligand 8-HQS has been chosen for application in uranium remediation of aqueous environments.

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Publication details

The article was received on 12 Apr 2017, accepted on 08 May 2017 and first published on 08 May 2017


Article type: Paper
DOI: 10.1039/C7DT01324H
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Oxocomplexes of U(VI) with 8-Hydroxyquinoline-5-Sulfonate in Solution: Structural Studies and Photophysical Behaviour

    M. L. Ramos, L. L. G. Justino, R. Barata, T. Costa, B. A. Nogueira, R. Fausto and H. D. Burrows, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01324H

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