Complexation and Thermodynamic Studies of a New Schiff base Ligand with Some Metallic ions in Nonaqueous Solvents by Conductometric Method

The complexation reactions between N-N′-Bis(5-bromo-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine Schiff base ligand and Ag+, Cd2+, Co2+, Cu2+, Hg2+, Ni2+, and Zn2+ ions were studied conductometrically in acetonitrile, dimethylformamide, ethanol, and methanol solvents at 5, 10, 15, and 25ºC. The formation constants of the resulting ML and M2L complexes were calculated from the computer fitting of the molar conductance-mole ratio data at different temperatures. The selectivity of the Schiff base ligand to the cations is depended the nature of the solvent. At 25ºC in acetonitrile solvent, the stability of the resulting complexes varied in the order Hg2+ > Ag+ > Cd2+ > Cu2+ > Co2+ > Zn2+ > Ni2+. It was found that the stability of the resulting complexes decreased with increasing the solvation ability of the solvent. The values of the thermodynamic parameters (ΔH°, ΔS° and ΔG°) for complexation reactions were obtained from the temperature dependence of the stability constants values (log Kf) using the Van’t Hoff plots. In most cases, the complexes were found to be an enthalpy and entropy stabilized.