Thermodynamic studies on metal complexes of Cd2+, Ni2+, Cu2+ and Co2+ with pyridine-2,6-dicarboxylic acid in water, methanol and water-methanol binary solvent systems at 298.15, 308.15 and 318.15 K by conductometric method

Khushbu K. Mehta, Raviprakash S. Chandra, Dhruvi R. Mehta and M. M. Maisuria

Abstract

Stability constants are measured for complexes of Cd2+, Ni2+, Cu2+ and Co2+ with pyridine-2,6-dicarboxylic acid(PDA) in water, methanol and water-methanol binary solvent systems at 298.15, 308.15 and 318.15 K by conductometric method. The result shows that the stoichiometry of the complexes of PDA with all metals in all binary solvent systems is 1:2 [ML2]. The logKf values of PDA-M2+ complexes in H2O-MeOH binary solvent systems increase with increasing % of MeOH and temperature. The ∆H0 and ∆S0 of the complexation reaction in the different H2O-MeOH binary solvent systems were evaluated by the temperature dependence of the formation constants using a linear least square analysis according to van’t Hoff equation.