THERMODYNAMICS OF 2,2',2''-TERPYRIDINECOPPER(II) COMPLEXES IN AQUEOUS-SOLUTION

The thermodynamic quantities relative to the protonation and the complexation of 2,2′,2′'-terpyridine with copper(II) ion have been determined at 25° and I=0.1 mol dm-3 (NaNO3). The ΔG{ring operator} data was obtained by potentiometric measurements; a copper selective electrode was employed for the study of the complexation equilibria. The ΔH{ring operator} values have been determined by direct calorimetry. The hydrolytic species, existing at pH>6 and their relative ΔG{ring operator} and ΔH{ring operator} values have also been obtained. From the thermodynamic data the importance of enthalpy and entropy terms in stabilizing the complexes is assessed. Moreover some considerations on the chelating effect are reported. © 1979 Verlag Chemie, GmbH.