Investigations and chemical speciation of ternary complexes of bivalent metal ions with cephalexine as primary ligand and glycine and valine as secondary ligands

Department of Chemistry, University of Delhi, Delhi-110 007, India

E-mail : dubeyr@mamraonline.com Fax: 91-11-27666250

Manuscript received 22 March 2004, accepted 7 December 2005

Studies on ternary complexes or bivalent metal ions viz. Cu^ll, Pb^ll, Ni^ll, zn^ll, co^ll, Cd^ll, Mo^ll, Mg^ll and
Ca^ll, hereafter, M(II), with cephalexine (HCEX) as primary ligand and glycine (Gly) and valine (Val) as secondary ligands in 1 : 1 : 1 ratio, have been investigated by potentiometric technique at μ = 0.1 M (NaCIO₄) and temp. = 25 ± 0.5 in aqueous medium. The stability constants and S_min values or the ternary complexes M(II)-HCEX-Gly (A) and M(II)-HCEX-Val (B) have been calculated. The results have been discussed in terms of electrostatic and metal-ligand interaction. To visualize the nature of equilibrium and to evaluate the calculated stability constants of ternary complexes, species distribution diagrams have been plotted.