Synthesis and Thermal Decomposition Kinetics of Uranium(VI) Complex with Unsymmetrical Schiff Base Ligand

A new unsymmetrical tetradentate Schiff base ligand N-(5-chloro-2-hydroxy-α-phenylbenzylidene)-N′-(2-hydroxy-3-methoxybenzylidene)-o-phenylenediamine (H₂L) was synthesized using 5-chloro-2-hydroxybenzophenone, o-phenylenediamine and o-vanillin. A solid UO₂(II) complex of this ligand [UO₂(HL)(NO₃)(H₂O)]·H₂O was prepared and characterized by elemental analyses, IR, UV, ¹H NMR spectra and molar conductance. The thermal decomposition kinetics of the complex for the third stage was studied under a non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as: dα/dt=A·e^−E/RT·3/2[(1−α)^−1/3−1]⁻¹. The kinetic parameters (E, A), activation entropy ΔS^≠ and activation free-energy ΔG^≠ were also gained: E=69.08 kJ/mol, ln A=20.63, r=0.9867, ΔS^≠= −79.84 J·mol⁻¹·K⁻¹ and ΔG^≠=120.6 kJ/mol.