Complexation of uranium(VI) with aromatic acids such as hydroxamic and benzoic acid investigated by TRLFS

The complex formation of uranium(VI) with salicylhydroxamic, benzohydroxamic, and benzoic acid was investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS). We observed in all three systems a decrease in the fluorescence intensity with increasing ligand concentration. All identified complexed uranyl species are of the type M_pL_qH_r. In the uranium(VI)-salicylhydroxamate system a 1: 1 complex with a stability constant of log β ₁₁₁ = 17.34±0.06 and a 1: 2 complex with a stability constant of log β ₁₂₂ = 35.0±0.11 was identified. Also in the uranium(VI)-benzohydroxamate system the stability constants are determined to be log β ₁₁₀ = 7.92±0.11 and log β ₁₂₀ = 16.88±0.49. In the uranium(VI)-benzoate system only a 1: 1 complex is existent with a stability constant of log β ₁₁₀ = 3.56±0.05.