Copper(II), nickel(II) and zinc(II) complexes of amino acids containing bis(imidazol-2-yl)methyl residues

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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 ([Cu2H-2L2]2+) containing [NH2, N-, N(Im)] 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 the species [Cu2L2]4+ 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 ([Cu3H-4L2]2+).

Original languageEnglish
Pages (from-to)373-382
Number of pages10
JournalInorganica Chimica Acta
Volume339
DOIs
Publication statusPublished - Nov 15 2002

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Keywords

  • Bis(imidazolyl)
  • EPR
  • Histidine
  • Potentiometry
  • Stability constants
  • Transition metal ion

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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