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

Abstract

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.

Keywords:

• Isothiosemicarbazone uranyl complexes
• spectral
• crystal structure
• TGA
• thermodynamic parameters

Acknowledgements

We thank Tulane University for support of the Tulane Crystallography Laboratory and the support of NSF-MRI Grant #1228232 for the purchase of the D8 diffractometer.