POTENTIOMETRIC AND SPECTROSCOPIC STUDIES OF TRANSITION-METAL COMPLEXES OF BIS(IMIDAZOLYL) AND BIS(PYRIDYL) DERIVATIVES OF AMINO-ACIDS

Copper(II) and zinc(II) complexes of H-Gly-BIMA (glycinamido-bis(imida zol-2-yl)methane) and copper(II), nickel(II), cobalt(II) and zinc (II) complexes of Prodipa ( prolineamido-bis (pyridin-2-yl) methane) were studied by potentiometry, electron paramagnetic resonance and visible spectroscopy. The data revealed that both ligands are ambidentate. Imi dazole and pyridine nitrogens of H-Gly-BIMA and Prodipa, respectively, are the exclusive binding sites in acidic media, but the metal bindin g ability of the bis(imidazolyl) residue is much higher than that of t he bis(pyridyl) ligand. The coordination of the amino, amide and imida zole/pyridine nitrogens was concluded around physiological pH, which r esulted in the formation of an imidazole bridged dimeric species in th e case of H-Gly-BIMA. (C) 1998 Elsevier Science S.A. All rights reserv ed.