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Structural characterization of the aqueous dimeric uranium(VI) species: (UO2)2CO3(OH)3−
Gückel, K.; Tsushima, S.; Foerstendorf, H.;
A combined theoretical and spectroscopic approach was used to refine structural data of the aqueous dimeric U(VI) species, (UO2)2CO3(OH)3−. Several isomer structures of this complex were already derived from previous X-ray absorption and NMR experiments (Szabó, Z. et al. J. Chem. Soc.-Dalton Trans., 2000, 3158-3161) but due to unequivocal results a distinct structure could not be determined and uncertainties remain. In this work, the Gibbs energies and U–U distances obtained from density functional theory (DFT) calculations predict two isomers, one with a carbonate ligand and one with two hydroxo groups as bridiging groups, as most likely structures. The experimental IR spectrum indicates a bidentate coordination of the carbonate ion and the presence of two spectroscopically specifiable uranyl moieties as it also is predicted by the spectra computed on the base of DFT. Taken together theoretical and experimental results the isomer with a carbonate ligand bridging the two uranyl units appears most likely to represent the predominat structure. Contributions to a small extent of an isomer with a non-bridging carbonate anion can not be completely ruled out.
Keywords: Speciation, ATR FT-IR, DFT calculations

Publ.-Id: 18569 - Permalink