Thermodynamic Study of Monoligand and Protonated Complexes of Copper(II) with Triglycine in Aqueous Solutions

The thermal effects of the interaction between triglycine solutions and Cu(NO₃)₂ solutions at 298.15 K with ionic strength from 0.2 to 1.0 (KNO₃) are measured via direct calorimetry. The enthalpies of CuL⁺, CuHL²⁺, CuHL${}_2^{+}$, CuH₂L${}_2^{2+}$ complexation are determined. A complete thermodynamic description of complexation processes is obtained. Based on an analysis of the thermodynamic parameters and the results from spectrophotometric measurements, conclusions are drawn regarding the structure of the investigated complexes.