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

Complex formation in solutions containing Ni2+ cations, glycine anions (Gly(-)), and beta-lactam antibiotics, namely, ampicillin (Amp), amoxicillin (Axn), and cephalexin (Cpx), is studied by pH-metric titration at 20 degrees C and an ionic strength of 0.1 (KNO3). Mixed-ligand complexes [NiGlyAmp], [NiGlyAxn], and [NiGly-Cpx], 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.