pH-metric and spectrophotometric studies on the binary and ternary complexes of copper(II) with 2,3-pyrazinedicarboxylic acid and some aliphatic and aromatic acids

Formation and stability of binary and ternary complexes of copper(II) with 2,3-pyrazinedicarboxylic acid as a primary ligand and some biologically important aliphatic, aromatic and heteroaromatic carboxylic acids (succinic, malic, anthranilic, phthalic, salicylic, thiosalicylic and 2-hydroxynicotinic acids) as secondary ligands were determined by potentiometric and spectrophotometric techniques. The determination were performed in a 20% (v/v) ethanol-aqueous medium. Deltalog K and log X values indicate the favoured formation of ternary complexes, compared to the binary ones. The order of stability of the complexes under investigation in terms of the nature of secondary ligands is examined and discussed.