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Study on interactions in divalent ion complexes with L-tartaric acid and Cu(II) binary and ternary complexes

S.A.A.Sajadi, A.A.Alamolhoda, A.R.Nazari

The acidity and stability constants ofM(TA) (TA:tartarate) and Cu(Phen)(TA) (Phen:1,10-phenanthroline) complexes, were determined by potentiometric pH titration. It is shown that the stability of the binary Cu(TA) and complexes is determined solely by the basicity of the carboxylate group. It is demonstrated that the equilibrium, Cu(Phen)2+ + Cu(TA) Cu(Phen)(TA) + Cu2+, is displacement due to the well known experience that mixed ligand complexes formed by a divalent 3d ion, a heteroaromatic N base and an O donor ligand possess increased stability. The other part of this displacement, which amount on average to an increased stability of the mixed ligand Cu(Phen)(TA) complexes of about 0.27 log unit. The stability constants of the 1:1 complexes formed between Cu2+ or Cu(Phen)2+ and TA2-, were determined by potentiometric pH titration in aqueous solution (I = 0.1M, NaNO3, 25°C). The order of the stability constants was reported.