Synthesis, identification, structural and thermal stability investigations on bipyridinium uranyl acetate

Bipyridinium uranyl acetate (2,2′-bipyridinium triacetatodioxouranate(VI)) was synthesised by slow evaporation, at room temperature, of a reaction mixture of uranyl acetate and bipyridine in molar ratio 1:6 in 2 mol l−1 acetic acid. The yellow crystals were examined by elemental analysis, X-ray powder diffraction, FT-IR spectroscopy, thermogravimetric–differential thermal analysis (TG–DTA). According to the elemental, TG analysis and spectroscopy investigations, it could be concluded that the general formula of the compound is (NC5H4-C5H4NH)UO2(CH3COO)3. Thermal decomposition of the compound takes place in several steps. In the first step, the compound releases acetic acid (in molar ratio 1:1) and consequently undergoes structural changes (Anderson rearrangement). This results with bipyridine complex formation, confirmed by elemental analysis and infrared (IR) spectroscopy. In the second step, the complex decomposes to UO2, which is partially oxidised to UO3. The intermediate and the final products of thermal analysis were identified by means of TG–DTA and X-ray powder diffraction. The final product of thermal decomposition is U3O8.