JBIC Journal of Biological Inorganic Chemistry

, Volume 10, Issue 1, pp 63–77

Heme-copper/dioxygen adduct formation relevant to cytochrome c oxidase: spectroscopic characterization of [(6L)FeIII-(O22−)-CuII]+

  • Reza A. Ghiladi
  • Hong-wei Huang
  • Pierre Moënne-Loccoz
  • Jay Stasser
  • Ninian J. Blackburn
  • Amina S. Woods
  • Robert J. Cotter
  • Christopher D. Incarvito
  • Arnold L. Rheingold
  • Kenneth D. Karlin
Original Article

DOI: 10.1007/s00775-004-0609-1

Cite this article as:
Ghiladi, R.A., Huang, H., Moënne-Loccoz, P. et al. J Biol Inorg Chem (2005) 10: 63. doi:10.1007/s00775-004-0609-1

Abstract

In the further development and understanding of heme-copper dioxygen reactivity relevant to cytochrome c oxidase O2-reduction chemistry, we describe a high-spin, five-coordinate dioxygen (peroxo) adduct of an iron(II)-copper(I) complex, [(6L)FeIICuI](BArF20) (1), where 6L is a tetraarylporphyrinate with a tethered tris(2-pyridylmethyl)amine chelate for copper. Reaction of 1 with O2 in MeCN affords a remarkably stable [t1/2 (rt; MeCN)≈60 min] adduct, [(6L)FeIII-(O22-)-CuII]+ (2) [EPR silent; λmax=418 (Soret), 561 nm], formulated as a peroxo complex based on manometry (1:O2=1:1; spectrophotometric titration, −40 °C, MeCN), mass spectrometry {MALDI-TOF-MS: 16O2, m/z 1191 ([(6L)FeIII-(16O22−)-CuII]+); 18O2, m/z 1195}, and resonance Raman spectroscopy (ν(O-O)=788 cm–1; Δ16O2/18O2=44 cm–1; Δ16O2/16/18O2=22 cm–1). 1H and 2H NMR spectroscopy (−40 °C, MeCN) reveals that 2 is the first heme-copper peroxo complex which is high-spin, with downfield-shifted pyrrole resonances (δpyrrole=75 ppm, s, br) and upfield shifted peaks at δ= −22, −35, and −40 ppm, similar to the pattern observed for the μ-oxo complex [(6L)FeIII-O-CuII](BArF) (3) (known S=2 system, antiferromagnetically coupled high-spin FeIII and CuII). The corresponding magnetic moment measurement (Evans method, CD3CN, −40 °C) also confirms the S=2 spin state, with μB=4.9. Structural insights were obtained from X-ray absorption spectroscopy, showing Fe–O (1.83 Å) and Cu–O (1.882 Å) bonds, and an Fe...Cu distance of 3.35(2) Å, suggestive of a μ-1,2-peroxo ligand present in 2. The reaction of 2 with cobaltocene gives 3, differing from the observed full reduction seen with other heme-Cu peroxo complexes. Finally, thermal decomposition of 2 yields 3, with concomitant release of 0.5 mol O2 per mol 2, as confirmed quantitatively by an alkaline pyrogallol dioxygen scavenging solution.

Keywords

Heme-copperIron(II)-copper(I) complexPeroxo complexMass spectrometryResonance Raman spectroscopyDioxygen adductModel compound

Supplementary material

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Copyright information

© SBIC 2004

Authors and Affiliations

  • Reza A. Ghiladi
    • 1
  • Hong-wei Huang
    • 2
  • Pierre Moënne-Loccoz
    • 2
  • Jay Stasser
    • 2
  • Ninian J. Blackburn
    • 2
  • Amina S. Woods
    • 3
  • Robert J. Cotter
    • 3
  • Christopher D. Incarvito
    • 4
  • Arnold L. Rheingold
    • 4
    • 5
  • Kenneth D. Karlin
    • 1
  1. 1.Department of ChemistryThe Johns Hopkins UniversityBaltimoreUSA
  2. 2.Environmental & Biomolecular Systems, OGI School of Science & EngineeringOregon Health & Science UniversityBeavertonUSA
  3. 3.Department of Pharmacology and Molecular SciencesThe Johns Hopkins School of MedicineBaltimoreUSA
  4. 4.Crystallography Laboratory, Department of ChemistryUniversity of DelawareNewarkUSA
  5. 5.Chemistry DepartmentUniversity of California, San DiegoLa JollaUSA