Mahmood Payehghadr - Department of Chemistry, Payame Noor University, PO Box ۱۹۳۹۵-۴۶۹۷, Tehran, Iran
Seied Ebrahim Hashemi - Department of Chemistry, Payame Noor University, PO Box ۱۹۳۹۵-۴۶۹۷, Tehran, Iran
Zarin Eshaghi - Department of Chemistry, Payame Noor University, PO Box ۱۹۳۹۵-۴۶۹۷, Tehran, Iran
Hadi Kargar - Department of Chemical Engineering, Ardakan University, P. O. Box: ۱۸۴, Ardakan, Yazd, Iran

The complexation reactions between N-N′-Bis(۵-bromo-۲-hydroxybenzylidene)-۲,۲-dimethylpropane-۱,۳-diamine Schiff base ligand and Ag+, Cd۲+, Co۲+, Cu۲+, Hg۲+, Ni۲+, and Zn۲+ ions were studied conductometrically in acetonitrile, dimethylformamide, ethanol, and methanol solvents at ۵, ۱۰, ۱۵, and ۲۵ºC. The formation constants of the resulting ML and M۲L 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 ۲۵ºC in acetonitrile solvent, the stability of the resulting complexes varied in the order Hg۲+ > Ag+ > Cd۲+ > Cu۲+ > Co۲+ > Zn۲+ > Ni۲+. 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.

complexation, Conductometric, Formation constants, Schiff bases, thermodynamic parameters