Dürr KL, Macpherson BP, Warratz R, Hampel F, Tuczek F, Helmreich M, Jux N, Ivanovic-Burmazovic I (2007)
Publication Type: Journal article, Original article
Publication year: 2007
Original Authors: Dürr K., Macpherson B., Warratz R., Hampel F., Tuczek F., Helmreich M., Jux N., Ivanović-Burmazović I.
Publisher: American Chemical Society
Book Volume: 129
Pages Range: 4217-4228
Journal Issue: 14
DOI: 10.1021/ja064984p
The synthesis and characterization of the Fe(III) complex of a novel crown ether-porphyrin conjugate, 5-N-(4-aza-18-crown-6)methyl-5 ,10,15,20-tetra-tert-butyl- 5-methyl-5,10,15,20-tetraphenylporphyrin (HPorph), as well as the corresponding hydroxo, dimeric, Fe(II), and peroxo species are reported. The crystal structure of [Fe(Porph)Cl]·H O·FeCl·C H·EtOH is also reported. [Fe(Porph) (DMSO)] and K[Fe(Porph)(O)] are high-spin species (Mössbauer data: δ = 0.38 mm s, ΔE = 0.83 mm s and δ = 0.41 mm s, ΔE = 0.51 mm s, respectively), whereas in a solution of reduced [Fe(Porph)-(DMSO) ] complex the low-spin [Fe(Porph)(DMSO) ] (δ = 0.44 mm s, ΔE = 1.32 mm s) and high-spin [Fe(Porph)(DMSO)] (δ = 1.27 mm s ΔE = 3.13 mm s) iron(II) species are observed. The reaction of [Fe(Porph)(DMSO)] with KO in DMSO has been investigated. The first reaction step, involving reduction to [Fe(Porph)(DMSO) ], was not investigated in detail because of parallel formation of an Fe-(III)-hydroxo species. The kinetics and thermodynamics of the second reaction step, reversible binding of superoxide to the Fe(II) complex and formation of an Fe(III)-peroxo species, were studied in detail (by stopped-flow time-resolved UV/vis measurements in DMSO at 25°C), resulting in k = 36 500 ± 500 M s, k = 0.21 ± 0.01 s (direct measurements using an acid as a superoxide scavenger), and K = (1.7 ± 0.2) × 10 (superoxide binding constant kinetically obtained as k/k), (1.4 ± 0.1) × 10, and (9.0 ± 0.1) × 10 M (thermodynamically obtained in the absence and in the presence of 0.1 M NBuPF , respectively). Temperature-dependent kinetic measurements for k (-40 to 25°C in 3:7 DMSO/CHCN mixture) yielded the activation parameters ΔH = 61.2 ± 0.9 kJ mol and ΔS = +48 ± 3 J K mol. The observed reversible binding of superoxide to the metal center and the obtained kinetic and thermodynamic parameters are unique. The finding that fine-tuning of the proton concentration can cause the Fe(III)-peroxo species to release O and form an Fe(II) species is of biological interest, since this process might occur under very specific physiological conditions. © 2007 American Chemical Society.
APA:
Dürr, K.L., Macpherson, B.P., Warratz, R., Hampel, F., Tuczek, F., Helmreich, M.,... Ivanovic-Burmazovic, I. (2007). Iron(III) complex of a crown ether-porphyrin conjugate and reversible binding of superoxide to its iron(II) form. Journal of the American Chemical Society, 129(14), 4217-4228. https://doi.org/10.1021/ja064984p
MLA:
Dürr, Katharina L., et al. "Iron(III) complex of a crown ether-porphyrin conjugate and reversible binding of superoxide to its iron(II) form." Journal of the American Chemical Society 129.14 (2007): 4217-4228.
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