EFFECTS OF MIXED-LIGAND COMPLEX-FORMATION ON DEPROTONATION OF AMIDE GROUPS IN N-BENZOYLGLYCINE AND N-(4-AMINOBENZOYL)GLYCINE

Stability constants of the binary complexes of the N-protected amino acids, N-benzoylglycine and N-(4-aminobenzoyl)glycine (pah) with copper(II) have been determined. Also the stability constants of the ternary complexes of the above systems with the secondary (B) ligands D,L-alanine (ala), 2,3-diamino-propionic acid (dap), 1,2-dihydroxybenzene-3,5-disulphonate (Tiron), pyridine-2-carboxylic acid (pie), L-histidine (his), and 2,2'-bipyridyl (bipy) have been evaluated. Then appropriate computer simulations, based on corresponding results are used to assess the influence of the secondary ligand's nature on the deprotonation of the amide groups of the ligrands hip and pah, used as primary (A) ligands in mixed-ligand complex systems. In the binary complexes of Cu(II) with hip and pah, deprotonations and coordination of the amide group could not be detected. However, the presence of B ligands containing aromatic N-donor atoms, permits deprotonation of the amide groups in both hip and pah.