Complex formation in nickel(II)-glycine-β-lactam antibiotic systems

Complex formation in solutions containing Ni²⁺ cations, glycine anions (Gly^?), and β-lactam antibiotics, namely, ampicillin (Amp), amoxicillin (Axn), and cephalexin (Cpx), is studied by pH-metric titration at 20°C and an ionic strength of 0.1 (KNO₃). Mixed-ligand complexes NiGlyAmp], NiGlyAxn], and NiGlyCpx], which are in equilibrium with the NiGly]⁺ complexes, are formed in the systems studied in a weakly alkaline medium. The formation constants of the complexes are determined. The distribution diagrams of the complex Ni(II) forms at different pH values of the solutions are constructed.