Study the thermodynamics of complex formation of Rare earth metal ions with substituted thiazole Schiff bases in mixed solvent media

Abstract

The Schiff bases derived from substituted aminothiazole i.e.2-4-Diamino thiazole and R-Substituted salicylaldehyde (R-5-CH3 and 5-Cl) or 2-hydroxy-1-naphthaldehyde i.e. (5MS)2DT, (5CS)2DT and (HN)2DT and Rare earth metal ion La III , Ce III , Pr III , Nd III , Sm III , Gd III , Tb III , Ho III , Dy III and Yb III Nitrate Salts. The stability constants of lanthanide metal ion complexes in mixed solvent media in ethanol-water 50:50 (v/v) at different ionic strength µ = 0.05, 0.1, 0.15 and 0.2 M (NaClO4) and at different temperature (35 0 C and 45 0 C) using Bjerrum pH metric technic as adopted by Irving Rossotti. The formation constants are determined by Half-Integral method. The stability constants of Rare earth metal (III) ion complexes have been to proportional to their ionic strength. The thermodynamic parameter (H, G and S) were determined. The negative free energy change (G) in each case indicates that the complexation is spontaneous. The enthalpy changes are exothermic. The positive values of S Indicates the reactions are entropically favoured.