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Speciation of uranyl nitrato complexes in acetonitrile and in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
Servaes K., Hennig C., Billard I., Gaillard C., Binnemans K. et al
European Journal of Inorganic Chemistry 2007/32 (2007) 5120 - 5126 - http://hal.in2p3.fr/in2p3-00203015
Chimie/Chimie inorganique
Speciation of uranyl nitrato complexes in acetonitrile and in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
K. Servaes, C. Hennig, I. Billard1, C. Gaillard1, K. Binnemans, C. Gorller-Walrand, R. Van Deun
1 :  DRS-IPHC - Département Recherches Subatomiques
CNRS : UMR7178 – IN2P3 – Université Louis Pasteur - Strasbourg I
23 rue du Loess - BP28 67037 Strasbourg cedex 2
France
Complex formation between the uranyl ion and nitrate ions in acetonitrile and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]) has been studied by absorption, magnetic circular dichroism (MCD) and uranium LIII EXAFS spectroscopy. The experimental results point to the existence of a trinitrate species [UO2(NO3)3]- with D3h symmetry in both solvents. The atomic distances in the uranium(VI) coordination sphere for the trinitrato complex in acetonitrile are U-Oax = 1.77 ± 0.01 Å and U-Oeq = 2.48 ± 0.01 Å. EXAFS data show that the uranyl ion in the ionic liquid is surrounded by six oxygen atoms in the equatorial plane at a distance of 2.49 ± 0.01 Å. The U-N distance of 2.92 ± 0.01 Å indicates a bidentate coordination of the nitrate group in both solvents. A structural comparison is made between the uranyl trinitrato complex anion [UO2(NO3)3]- and the uranyl tricarbonato complex anion [UO2(CO3)3]4-. No evidence is found for the presence of uranyl nitrato complexes in aqueous solution. The optical absorption, MCD and EXAFS spectra resemble those of the hydrated free uranyl ion. There are two axial oxygen atoms at 1.77 ± 0.01 Å and five equatorial oxygen atoms at 2.41 ± 0.01 Å. These values agree well with structural parameters obtained for the uranyl aqua ion

Articles dans des revues avec comité de lecture
2007
European Journal of Inorganic Chemistry
Publisher Wiley-VCH Verlag
ISSN 1434-1948 (eISSN : 1099-0682)
2007/32
5120 - 5126
Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007

EXAFS spectroscopy – Ionic liquids – Uranium – UV/Vis spectroscopy – X-ray absorption spectroscopy