Mixed-ligand complex formation in the copper(II)-salicylate-ammonia and in the copper(II)-salicylate-pyridine systems

Mixed ligand complexation between Cu(ll) ion, salicylate ion (sal) and a nitrogen base which acts as unidentate ligand, pyridine (py) or ammonia, is studied potentiometrically at 25 °C and in 1.0 mole dm-3 ionic media (KN03 or NH4N03 respectively). Experimental data are analysed using both Miniquad and Letagrop programs ; the performances of these programs are compared. Analysis of variance in the case of copper-ammonia complexation is performed. All the species present in solution in both systems are identified and their formation constants are evaluated. Distribution plots of the mixed complexes at several concentration ratios of their constituents are obtained. Stabilization of these mixed-ligand complexes. Cu(sal)(py)2 and Cu(sal)(NH3)2, is estimated and different stabilizing factors are discussed