Chemical equilibrium studies on some bivalent metal chelates of cephalexin

The stability constants of metal chelates ofcephalexin (an antibiotic drug) with Co", Ni^II, Cu^II, Zn^II ions have been evaluated pH-metrically in aqueous solutions at 25 and 30° and 0.1 M (NaCIO4) ionic strength. The ternary formation constants of metal chelates MLA, where M = bivalent ions, L ^ cephalexin and A = alpha-alanine, have also been determined potentiometrically; cephalexin behaves as primary ligand in presence of a-alaninc as the secondary ligand. Stability constants arc discussed in terms of the basicity of ligand, statistical and stereochemical phenomenon. Thermodynamic parameters have also been evaluated and discussed.