Equilibrium studies of ternary chelates of some divalent metal ions with cephalosporins and (alpha)-alanine

The formation of bioligand chelates of some divalent metal ions Mn, Co, Ni, Cu, Zn, Cd and Mg with cephaloridine as primary ligand (L) and (alpha)-alanine as the secondary ligand (A) has been carried out pH-metrically at 25 and 35 and at constant ionic strength, (mu) = 0.1 M (NaC104). The stability constants follow the order : Cu" > Zn" > Co" > Ni" > Cd" > Mg" > Mn". The log K values are less negative than -0.6, suggesting favoured formation of ternary complexes. Stability constants have been evaluated and discussed in terms of the basicity of the ligand, statistical and stereochemical phenomenon and compared with that of cephalexin drug.