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Issue 8, 2010
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Studies on an iron(iii)-peroxo porphyrin. Iron(iii)-peroxo or iron(ii)-superoxo?

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We demonstrate that a one electron reduced product of the heme iron dioxygen adduct exists in solution not only as the commonly accepted iron(III)-peroxo species, but coexists with its isomeric iron(II)-superoxo form. This unusual reduced metal-superoxide adduct [M(II)-O2] is recently reported as a reactive intermediate in the case of non-heme extradiol dioxygenases and could also be generated by cryoreduction of a heme FeII-O2 adduct. The existence of iron(II)-superoxo species in solution is consistent with IR, EPR, mass and Mössbauer spectra. The equilibrium between heme iron(III)-peroxo and iron(II)-superoxo forms is supported by density functional theory and explains our previous finding that upon release of coordinated (su)peroxide a corresponding iron(II) complex remains. These results shed new light on the nature of heme iron(III)-peroxo species that are key intermediates in the metalloenzyme-catalyzed dioxygen and hydrogen peroxide activation.

Graphical abstract: Studies on an iron(iii)-peroxo porphyrin. Iron(iii)-peroxo or iron(ii)-superoxo?

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Supplementary files

Article information

29 Sep 2009
30 Nov 2009
First published
13 Jan 2010

Dalton Trans., 2010,39, 2049-2056
Article type

Studies on an iron(III)-peroxo porphyrin. Iron(III)-peroxo or iron(II)-superoxo?

K. Duerr, J. Olah, R. Davydov, M. Kleimann, J. Li, N. Lang, R. Puchta, E. Hübner, T. Drewello, J. N. Harvey, N. Jux and I. Ivanović-Burmazović, Dalton Trans., 2010, 39, 2049
DOI: 10.1039/B920237D

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