Metal complexes of some peptide derivatjves. Part-XV. Mixed ligand complex formation of copper(ll) with some N-benzenesulfonyldipeptides as primary ligands and acetate, 2-methylbenzimidazole, glycinate and bipyridine as Seondary ligands

Department of Chemtstry, Untverstty of Calcutta, Umverstty College of Science, 92, A PC Road!

Kolkata-700 009, India

E-mail : gurunath@cucc er net 111   Fax : 91-33-2413222/-3519755

Bengal Chemicals and Pharmaceutical Works, Kolkata-700 009, India

Manuscript received 24 Novembe1 2000

Potentiometric Investigation on the complex fo1 mation equihbria of ( u11 with N-benzenesulfonyl derivatives of  some dipeptides, viz glycylglycine, glvcy 1-β-alanine and β-alanylglycine, hercaltur, abbreviated as NBSGG, NBSGB Jnd NBSBG (AH₂) respectively, 1n the presence of typical secondary ligands, viz acetate (ac-), 2-methylbenzimidazone (bz), glycineto (gly-) and bipyridine (bipy), hereatfter, B, provides evidencee of formation of varietiecs of binary and ternary complexes of the types Cu(AH), Cu(H ₁AH), Cu(H ₁A), Cu(H_{_1}A)(OH), Cu(B), Cu(B), Cu(B),(AH) and Cu(B)(H ₁AH) and Cu(B)(H ₁A)Stabilihty constants of the complexes Jt 25 ± 1⁰, in aqueous solution at a constant ionic strength, I= 0 1 M (NaNO₃) have been determined and the complex formation equihbria elucidated on the basis' of spectation curves the sulfonamidodipeptuide ligands ( A H₂) provide three coordinating groups -COOH, -CONH-, and -SO₂NH-, and show ambidentism in forming the binary and the ternary complexes depending upon the denticity, ᶷ-basicity and ᶮ-acidity of the B-ligands the ternary complexes are found to be Stable in the intermediate pH range (5-8) Above pH 8, the mixed ligand complexes derived from all the AH₂ and B ligands decompose to produce either the fully deprotonated binary complexes, Cu(H ₁A)^- or the ternary hydroxo complexes Cu(H ₁A)(OH) ² depending upon the nature of the B ligands.