VIVO complexes of bis(imidazol-2-yl) derivatives: A potentiometric, spectroscopic and DFT study

Katalin Várnagy, Timea Csorba, Dóra Kiss, Eugenio Garribba, Giovanni Micera, Daniele Sanna

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Abstract

The complexation of the VIVO ion with four amino acid derivatives of bis(imidazol-2-yl)methylamine [N-glycyl-bis(imidazol-2-yl) methylamine = Gly-BIMA, N-α-aspartyl-bis(imidazol-2-yl)methylamine = α-Asp-BIMA, N-α-glutamyl-bis(imidazol-2-yl)methylamine = α-Glu-BIMA and N-histidyl-bis(imidazol-2-yl)methylamine = His-BIMA] was studied in aqueous solution through the combined application of potentiometric and spectroscopic (UV/Vis and EPR) techniques. For comparison, the complexing capability of three simple bis(imidazol-2-yl) derivatives [bis(imidazol-2-yl) methane = BIM, bis-(imidazol-2-yl)methylamine = BIMA and bis(imidazol-2-yl)- nitromethane = BINM] and two benzyloxycarbonyl (Z) derivatives (Z-Gly-BIMA and Z-Ala-BIMA) was reported. Mono-and bis-chelated species with the (N im, Nim) donor set were formed in both acid and neutral pH conditions, with the bis-chelated complexes being characterised by a cis-trans isomerism. In the basic pH range the complexation process continues with the formation of a mono-hydroxo cis-VOL2H-1 complex in systems with BIM, BIMA and BINM, and with the deprotonation and coordination of the amide nitrogen to give VOLH-1 and VOLH-2 in those with Gly-BIMA, α-Asp-BIMA, α-Glu-BIMA and His-BIMA. The results demonstrate that the bis(imidazol-2-yl)methyl residue is an anchoring group of intermediate strength, capable of avoiding extensive hydrolysis of the V IVO ion in the presence of a slight excess of ligand (L/M from 3:1 to 5:1). DFT calculations with progressively more complex basis sets were performed in order to obtain information on the structure of the VOLH -1 and VOLH-2 complexes. Finally, a discussion on the 51V anisotropic parallel hyperfine coupling constant (A ) of VOLH-1 and VOLH-2 and on the EPR properties connected to the V-N-(amide) bond in VIVO complexes is presented.

Original languageEnglish
Pages (from-to)4884-4896
Number of pages13
JournalEuropean Journal of Inorganic Chemistry
Issue number31
DOIs
Publication statusPublished - Nov 16 2007

Keywords

  • Bioinorganic chemistry
  • Density functional calculations
  • EPR spectroscopy
  • Vanadium
  • pH potentiometry

ASJC Scopus subject areas

  • Inorganic Chemistry

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