Some oxovanadium(IV) complexes, namely bis(1,1,1-trifluro-2,4-pentanedionato-$O,O'$) oxovanadium (IV), [VO(tfac)₂(H₂O)], bis(1-phenyl-2,4-pentanedionato-$O,O'$)oxovanadium(IV), [VO(phac)₂(H₂O)], bis(1,3-diphenyl-2,4-pentanedionato-$O,O'$)oxovanadium(IV), [VO(dphac)₂ (H₂O)], of the type [VO(O₄)] and bis(pyrolidineaniline)oxovanadium(IV), [VO(pyran)₂(H₂O)], bis(𝑝-hydroxypyrolidineaniline) oxovanadium(IV), [VO(𝑝-hydroxypyran)₂(H₂O)], bis(𝑝-methoxypyrolidineaniline)oxovanadium(IV), [VO(𝑝-MeOpyran)₂ (H₂O)], bis(𝑝-chloropyrolidineaniline)oxovanadium(IV), [VO(𝑝-chloropyran)₂(H₂O)], bis(𝑝-bromopyrolidineaniline)oxovanadium(IV), [VO(𝑝-bromopyran)₂(H₂O)], bis(𝑝-cyano pyrolidineaniline)oxovanadium(IV), [VO(𝑝-cyanopyran)₂(H₂O)], and bis(pyrolidinebenzylamine)oxovanadium(IV), [VO(pyrbz)₂(H₂O)], of the type [VO(N₄)] were synthesized and characterized by IR, UV-Vis, mass spectrometry, elemental analysis, magnetic moment and thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The number of steps and, in particular, the starting temperature of decomposition of these complexes depends on the equatorial ligand. Also, formation constants of the complexes have been determined by UV-Vis absorption spectroscopy through titration of the ligands with the metal ions at constant ionic strength (0.1 M NaClO₄) and at 25°C. According to the thermodynamic studies, as the steric character of the ligand increases, the complexation tendency to VO(IV) center decreases. Also, the ab initio calculations were carried out to determine the structural and the geometrical properties of the complexes.

Uranyl(VI) complexes with unsymmetrical N₂O₂ Schiff base ligands were synthesized and characterized. Their characterization was performed using UV-Vis, ¹H NMR, cyclic voltammetry, single-crystal X-ray crystallography, IR, TG and C.H.N. techniques. X-ray crystallography of the complexes show that beside coordination of the tetradentate Schiff base, one DMF molecule is also coordinated. In order to investigate the effect of the substitutional groups of the Schiff base on the oxidation and reduction potentials, we used the cyclic voltammetry method. Electrochemistry of these complexes showed that the presence of electron releasing groups accelerates oxidation of the complexes. The kinetics of thermal decomposition was studied using thermal gravimetric method (TG) and Coats-Redfern equation. According to Coats-Redfern plots, the kinetics of thermal decomposition of the studied complexes is first-order in all stages. Also the kinetics and mechanism of the exchange reaction of the coordinated solvent with tributylphosphine was carried out in solution, using spectrophotometric method. As a result, the second order rate constants at four temperatures and the activation parameters were calculated showing an associative mechanism for all corresponding complexes. It was concluded that the steric and the electronic properties of the complexes influence the reaction rate significantly.