Multiple equilibria involved in some nickel(II) mixed ligand complex systems containing catecholic and dipeptide ligands

Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627 012, India Manuscript received 10 February 1999, accepted 9 July 1999 Multiple equilibrium studies on NiII-dopamineklopa(A)-glycyl-L-tryosine and L-tyrosylglycine(B) systems show the formation of NiABH2, NiABH or NiAB mixed ligand complexes. The results indicate that dopa is ambidentate, i.e. in NiABH2 species it binds the metal ion in a glycine-like mode, while it coordinates in a pyrocatecholic mode in NiABH and NiAB complexes. Dopamine(A) binds in a pyrocatechol mode in its mixed ligand complexes. Both the dipeptide(B) ligands bind via N-amino and O-peptide groups in all the mixed ligand complexes