DETERMINATION OF STABILITY CONSTANT OF CU (II)-NICOTINATE COMPLEX BY pH-METRIC STUDIES

Abstract

Nicotinic acid (pyridine-3-carboxylic acid), Niacin forms complexes with many metals. It may behave as mono, bi and tri dentate ligand but mostly co-ordinates as monodentate ligand.

Complex formation of Niacin with different metals is a pH dependent reaction. In this study potentiometric results were used for the calculation of stability constant. These results show that complexes of Nicotinic acid and Cu, forms (like ML, ML₂) at different pH. The stability constant was also calculated at different temperature (35 ?C, 40 ?C, 45 ?C, 50 ?C). pH-metric titration was also done by different mole ratios and results shows that best ratio is 1:2. Thermodynamic values ?H, ?S and ?G were determined by stability constant (at different temperature), these values suggests that ML₂ of Cu (II)-Nicotinate complexes are more stable than ML₁ Cu (II)-Nicotinate complex.