Further insights into the spectroscopic properties, electronic structure, and kinetics of formation of the heme-peroxo-copper complex [(F 8TPP)FeIII-(O22-)-Cu II(TMPA)]+

Reza A. Ghiladi, Eduardo E. Chufán, Diego Del Río, Edward I. Solomon, Carsten Krebs, Hanh Huynh Boi, Hong Wei Huang, Pierre Moënne-Loccoz, Susan Kaderli, Marcus Honecker, Andreas D. Zuberbühler, Lisa Marzilli, Robert J. Cotter, Kenneth D. Karlin

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Abstract

In the further development and understanding of heme-copper O 2-reduction chemistry inspired by the active-site chemistry in cytochrome c oxidase, we describe a dioxygen adduct, [(F8TPP)Fe III-(O22-)-CuII(TMPA)](ClO 4) (3), formed by addition of O2 to a 1:1 mixture of the porphyrinate-iron(II) complex (F8TPP)FeII (1a) {F 8TPP = tetrakis(2,6-difluorophenyl)porphyrinate dianion} and the copper(I) complex [(TMPA)CuI(MeCN)](ClO4) (1b) {TMPA = tris(2-pyridylmethyl)amine}. Complex 3 forms in preference to heme-only or copper-only binuclear products, is remarkably stable {t1/2 (RT; MeCN) ≈ 20 min; λmax = 412 (Soret), 558 nm; EPR silent}, and is formulated as a peroxo complex on the basis of manometry {1a/1b/O2 = 1:1:1}, MALDI-TOF mass spectrometry {16O2, m/z 1239 [(3 + MeCN)+]; 18O2, m/z 1243}, and resonance Raman spectroscopy {ν(O-O) = 808 cm-1; Δ 16O2/18O2 = 46 cm-1; Δ16O2/16/18O2 = 23 cm -1}. Consistent with a μ-η21 bridging peroxide ligand, two metal-O stretching frequencies are observed {ν(Fe-O) = 533 cm-1, ν(Fe-O-Cu) = 511 cm-1}, and supporting normal coordinate analysis is presented. 2H and 19F NMR spectroscopies reveal that 3 is high-spin {also μB = 5.1 ± 0.2, Evans method} with downfield-shifted pyrrole and upfield-shifted TMPA resonances, similar to the pattern observed for the structurally characterized μ-oxo complex [(F8TPP)Fe III-O-CuII(TMPA)]+ (4) (known S = 2 system, antiferromagnetically coupled high-spin FeIII and CuII). Mössbauer spectroscopy exhibits a sharp quadrupole doublet (zero field; δ = 0.57 mm/s, |ΔEQ| = 1.14 mm/s) for 3, with isomer shift and magnetic field dependence data indicative of a peroxide ligand and S = 2 formulation. Both UV-visible-monitored stopped-flow kinetics and Mössbauer spectroscopic studies reveal the formation of heme-only superoxide complex (S)(F8TPP)FeIII-(O2 -) (2a) (S = solvent molecule) prior to 3. Thermal decomposition of μ-peroxo complex 3 yields μ-oxo complex 4 with concomitant release of ∼0.5 mol O2 per mol 3. Characterization of the reaction 1a/1b + O2 → 2 → 3 → 4, presented here, advances our understanding and provides new insights to heme/Cu dioxygen-binding and reduction.

Original languageEnglish (US)
Pages (from-to)3889-3902
Number of pages14
JournalInorganic chemistry
Volume46
Issue number10
DOIs
StatePublished - May 14 2007

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All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Ghiladi, R. A., Chufán, E. E., Del Río, D., Solomon, E. I., Krebs, C., Boi, H. H., Huang, H. W., Moënne-Loccoz, P., Kaderli, S., Honecker, M., Zuberbühler, A. D., Marzilli, L., Cotter, R. J., & Karlin, K. D. (2007). Further insights into the spectroscopic properties, electronic structure, and kinetics of formation of the heme-peroxo-copper complex [(F 8TPP)FeIII-(O22-)-Cu II(TMPA)]+. Inorganic chemistry, 46(10), 3889-3902. https://doi.org/10.1021/ic061726k