Structural and Solution Characterization of Mononuclear Vanadium(IV) Complexes That Help To Elucidate the Active Site Structure of the Reduced Vanadium Haloperoxidases

Brent J. Hamstra, Andrew L P Houseman, Gerard J. Colpas, Jeff W. Kampf, Russell LoBrutto, Wayne Frasch, Vincent L. Pecoraro

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117 Scopus citations

Abstract

The complexes [VO(H2O)ada] (1), [VO(H2O)Hheida] (2), and [VO(H2O)aeida] (3) (H2ada, N-(carbamoylmethyl)-iminodiacetic acid; H3heida, N-(2-hydroxyethyl)iminodiacetic acid; H2aeida, N-(2-aminoethyl)iminodiacetic acid) were synthesized and crystallographically characterized. Crystallographic parameters for 1·2H2O: monoclinic, space group P21/c (No. 14), a = 7.327(2) Å, b = 23.386(7) Å, c = 7.258(3) Å, α = 90°, β = 110.95(2)°, γ = 90°, V = 1204.6(7) Å3, Z = 4, R1 = 0.0353, and wR2 = 0.0848. Crystallographic parameters for 2·H2O: orthorhombic, space group Pbca (No. 61), a = 10.512(2) Å, b = 11.727(2) Å, c = 16.719(5) Å, α = 90°, β = 90°, γ = 90°, V = 2060.6(8) Å3, Z = 8, R1 = 0.0297, and wR2 = 0.0758. Crystallographic parameters for 3: monoclinic, space group P21/c (No. 14), a = 6.785(1) Å, b = 9.714(2) Å, c = 14.959(2) Å, α = 90°, β = 95.12(1)°, γ = 90°, V = 982.2(3) Å3, Z = 4, R1 = 0.0298, and wR2 = 0.0762. In each structure, the tetradentate ligand is disposed so that the tertiary nitrogen is bound trans to the vanadyl oxo, and the rest of the donors occupy equatorial coordination positions. In solution, the structural integrity of these compounds is maintained as observed by UV/visible and EPR spectroscopies, and axial ligation by nitrogen is inferred on the basis of ESEEM spectroscopy. The implications of this study with respect to understanding the coordination environment of VO2+ in the reduced, inactive form of vanadium bromoperoxidase (VBrPO) are discussed, and it is proposed that significant changes in the coordination environment of vanadium in VBrPO occur upon its reduction, which may provide a plausible explanation for its irreversible inactivation.

Original languageEnglish (US)
Pages (from-to)4866-4874
Number of pages9
JournalInorganic chemistry
Volume36
Issue number21
DOIs
StatePublished - 1997

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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