Infrared and Raman spectroscopic study of uranyl complexes: hydroxide and acetate derivatives in aqueous solution
Abstract
Infrared-attenuated total reflectance (IR-ATR) and Raman spectroscopies are used to identify the complexed species of uranyl with hydroxide and acetate in aqueous solutions as a function of pH and metal-to-ligand ratio. Three stoichiometries (UO2CH3COO+, UO2(CH3COO)2 and UO2(CH3COO)3−) are observed via irregular shifts of the uranyl stretching signals. The acetate vibrational modes ν(CO2) and ν(CC), allow the identification of two different ligand structures as a function of the complex stoichiometries: UO2CH3COO+ and one ligand of UO2(CH3COO)2 are pseudobridging, the second acetate of UO2(CH3COO)2 being bidentate. There is still uncertainty on the presence of a pseudobridging acetate in UO2(CH3COO)3−.