Copper(II), nickel(II) and zinc(II) complexes of Phe-BIMA and His-BIMA were studied by potentiometric, UV-Vis and EPR spectroscopic methods. The nitrogen donor atoms of the bis(imidazol-2-yl)methyl residues were described as the primary metal binding sites in all systems studied. Deprotonation and coordination of the terminal amino and amide nitrogen atoms took place in the copper(II) complexes of both ligands and resulted in the formation of dinuclear complexes containing tridentate ligands and imidazole bridging. The presence of the histidyl side chain provides a great versatility in the complex formation reactions of His-BIMA. The existence of a dinuclear species was detected in slightly acidic solution and its structure was described as a mixture of three isomeric forms. Deprotonation of the imidazole-N(1)H donor functions was detected under slightly alkaline conditions with pK values of 8.13 and 8.93. An excess of copper(II) ions shifted this reactions even into the slightly acidic pH range and resulted in the formation of a trinuclear complex.
Copper(II), nickel(II) and zinc(II) complexes of amino acids containing bis(imidazol-2-yl)methyl residues.
Sanna D;
2002
Abstract
Copper(II), nickel(II) and zinc(II) complexes of Phe-BIMA and His-BIMA were studied by potentiometric, UV-Vis and EPR spectroscopic methods. The nitrogen donor atoms of the bis(imidazol-2-yl)methyl residues were described as the primary metal binding sites in all systems studied. Deprotonation and coordination of the terminal amino and amide nitrogen atoms took place in the copper(II) complexes of both ligands and resulted in the formation of dinuclear complexes containing tridentate ligands and imidazole bridging. The presence of the histidyl side chain provides a great versatility in the complex formation reactions of His-BIMA. The existence of a dinuclear species was detected in slightly acidic solution and its structure was described as a mixture of three isomeric forms. Deprotonation of the imidazole-N(1)H donor functions was detected under slightly alkaline conditions with pK values of 8.13 and 8.93. An excess of copper(II) ions shifted this reactions even into the slightly acidic pH range and resulted in the formation of a trinuclear complex.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
