Structural and spectroscopy studies of complexes of the uranyl ion with 2,2′-bipyridine-N,N′-dioxide

Authors:

• Zbigniew Hnatejko,
• Stefan Lis,
• Zdzisław Stryia,
• Przemystaw Starynowicz

Abstract

2,2′-Bipyridine-N,N′-dioxide (bypO₂ = L) complexes of the composition [UO₂(bypO₂)2(NO₃) ₂]·2H₂O (UO₂-L₂-NO ₃), [UO₂(bypO₂)₂H ₂O](C1O₄)₂ (UO₂-L ₂-ClO₄) and [UO₂bypO₂(H ₂O)₂SO₄] (UO2-L-SO4) have been prepared by the reactions of the respective hydrated uranyl salts with the bypO₂ ligand in water. The structures of the complexes were elucidated using elemental and thermal analyses, IR and luminescence spectroscopy as well as luminescence lifetime measurements. The IR spectra show that the bonding between uranium and bypO₂, as well as uranium and water or a counter ion (NO ₃^- and SO₄^2-) is formed. The nitrate or sulfate groups coordinate to the central metal ions in a monodentate manner. From TG-DTA curves, the nature of the water molecules present in the complexes and the decomposition temperature of the dehydrated uranyl complexes were determined. The thermal stability of the anhydrous uranyl complexes increases in the series: (UO₂-L₂-NO₃) < (UO ₂-L₂-ClO₄) < (UO₂-L-SO ₄). All the compounds show green-yellow intense luminescence. The main fluorescence bands and the emission lifetimes in these complexes were determined. The luminescence spectra of all the prepared complexes differ from each other with respect to their peak maxima positions. The luminescence lifetimes also vary. The structure of the (UO₂-L-SO₄) complex was determined by X-ray single-crystal analysis. © 2010 Elsevier Ltd. All rights reserved.