Dioxidouranium isothiosemicarbazone coordination compounds: synthesis, characterization, crystal structure, and thermal behavior

Five uranium complexes with UO2L′(solv) formula (L′: prepared by condensation reaction between 2-hydroxyacetophenon S-pentyl isothiosemicarbazone (H2L) and 5-bromosalicylaldehyde (Sal); solv: ethanol (1), 2-propanol (2), 2-butanol (3), ethylene glycol (4), 1,2-propanediol (5)) were synthesized through template reactions between H2L, Sal, and UO2(CH3COO)2∙2H2O for 1 and recrystallization of 1 in appropriate solvents for the other complexes. The compounds are characterized by melting point, elemental analyses, FT-IR, 1H NMR, 13C NMR, TGA, and X-ray crystallography. Molecular structures of the obtained crystals, determined by X-ray diffraction analysis, showed that the complexes have distorted pentagonal bipyramidal geometry. In all complexes, the bianionic tetradentate ligand (N2O2) with phenolic oxygens (O3, O4), thioamidic and azomethine nitrogen donor atoms is coordinated to the metal center in equatorial positions and the solv molecules occupied the fifth equatorial site and finally linear UO2 is located in axial position. The thermal behavior of the complexes was studied with TGA and DTG data and the results revealed three weight loss stages. The Coats–Redfern method is used for all degradation steps to determine kinetic parameters.