Thermodynamics of complex formation of rare earth metal ions with schiff bases in mixed solvent media

Abstract

Proton-ligand stability constants of N-phenyl-2-hydroxy- 5- chioroacetophenoneimine(I) and N-ɑ-naphthyl- 2-hydroxy- 5-chioroacetophenoneimine(II) and metal-ligand stability constants of their complexes with La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(I1I), Dy(III) and Yb(III) have been determined at 25°, 35° and 50°C (± 0.02°C) and and μ =0.l <em>M</em>(NaClO₄) in 60% ethanol-water medium. The thermodynamic parameters for the formation of 1:1 and 1:2 complexes have been calculated. The metal complexes of the ligand(I) are observed to be enthalpy- and entropy-stabilized. However, the positive values of enthalpy and entropy changes in the case of the 1:2 complexes of ligand(II) show the predominance of the entropy effect.