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

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.