Thermodynamic and spectrophotometric study of copper(II) and cadmium(II) homo- and hetero-nuclear complexes with L-histidylglycine in an aqueous medium

Abstract

Homo- and hetero-nuclear complexes of copper(II) and cadmium(II) with L-histidylglycine have been investigated by potentiometry, visible spectrophotometry, and calorimetry in aqueous medium, at T= 25 °C and I= 0.1 mol dm^–3(KNO₃). Gibbs functions obtained by potentiometry, combined with calorimetric enthalpies, gave the entropies of formation of the complex species. Experimental data have been obtained for the following species (L^–= histidylglycinate anion): HL, H₂L⁺, H₃L²⁺, [CuL]⁺, [CuL₂], [CuLH]²⁺, [CuL₂H]⁺, [Cu₂LH_–1]²⁺, [Cu₂L₂H_–2], [CdL]⁺, [CdL₂], [CdLH]²⁺, [CuCdLH_–1]²⁺, [CuCdLH_–2]⁺. In general, the structures predicted on the basis of the spectrophotometric and thermodynamic results are in good agreement.