Potentiometric, spectroscopic and DFT study of the VIVO complexes formed by Di(pyridin-2-yl) ligands

Luisa Pisano, Dóra Kiss, Katalin Várnagy, Daniele Sanna, Giovanni Micera, Eugenio Garribba

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Abstract

The coordinating properties of a series of di(pyridin-2-yl) derivatives towards the VIVO2+ ion have been studied through the combined application of potentiometric and spectroscopie (electronic absorption and EPR spectroscopies) methods. In particular, di(pyridin-2-yl)amine (DPA), di(pyridin-2-yl)methane (DPM), di(pyridin-2-yl) ketone (DPK), di(pyridin-2-yl)methanol (DPMO), 2-acetylpyridine (2-AP) and 2-hy-droxymethylpyridine (2-HMP), and two amino acid derivatives of di(pyridin-2-yl)methylamine (DPMA), namely N-gly-cyl-DPMA and N-histidyl-DPMA, have been examined. The stability constants of proton and VIVO complexes (logβ) were measured at 25 °C and at a constant ionic strength of 0.2 M (KC1). The results show that the simple di(pyridin-2-yl) derivatives having only pyridine nitrogen atoms form mono-che-lated species with the (Npyr, Npyr) donor set, whereas those provided with carbonyl or hydroxy groups form mono- and bis-chelated complexes with (N pyr, CO) or (Npyr, O∼) coordination. The square pyramidal species with 2×(Npyr, O-) coordination exists in equilibrium with the octahedral isomer, which has an axially bound water molecule and is characterized by an anomalously low value of the 51V hyperfine coupling constant along the z-axis (Az). DFT calculations were used to optimize the geometry of the complexes and to predict the Az values measured in the EPR spectra for the penta- and hexacoordinate complexes formed by DPK, DPMO, 2-AP and 2-HMP and for the [VOLH-1]+ and [VOLFL-2] species formed by the amino acid derivatives of DPMA.

Original languageEnglish
Pages (from-to)2362-2374
Number of pages13
JournalEuropean Journal of Inorganic Chemistry
Issue number16
DOIs
Publication statusPublished - Jun 1 2009

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Keywords

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

ASJC Scopus subject areas

  • Inorganic Chemistry

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