Infrared and Raman spectroscopic study of uranyl complexes: hydroxide and acetate derivatives in aqueous solution

Infrared-attenuated total reflectance (IR-ATR) and Raman spectroscopies are used to identify the complexed species of uranyl with hydroxide and acetat e in aqueous solutions as a function of pH and metal-to-ligand ratio. Three stoichiometries (UO2CH3COO+, UO2(CH3COO)(2) and UO2(CH3COO)(3)(-)) are obs erved via irregular shifts of the uranyl stretching signals. The acetate vi brational modes nu(CO2) and nu(CC), allow the identification of two differe nt ligand structures as a function of the complex stoichiometries: UO2CH3CO O+ and one ligand of UO2(CH3COO)(2) are pseudobridging, the second acetate of UO2(CH3COO)(2) being bidentate. There is still uncertainty on the presen ce of a pseudobridging acetate in UO2(CH3COO)(3)(-). (C) 1998 Elsevier Scie nce B.V. All rights reserved.