Functional mimic of dioxygen-activating centers in non-heme diiron enzymes

Mechanistic implications of paramagnetic intermediates in the reactions between diiron(II) complexes and dioxygen

Dongwhan Lee, Brad Pierce, Carsten Krebs, Michael P. Hendrich, Boi Hanh Huynh, Stephen J. Lippard

Research output: Contribution to journalArticle

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Abstract

Two tetracarboxylate diiron(II) complexes, [Fe2(μ-O2CArTol)2 (O2CArTol)2 (C5H5N)2] (1a) and [Fe2μ-O2CArTol)4 (4-tBuC5H4N)2] (2a), where ArTolCO2- = 2,6-di(p-tolyl)benzoate, react with 02 in CH2Cl2 at -78°C to afford dark green intermediates 1b (λmax ≅ 660 nm; ε = 1600 M-1 cm-1) and 2b λmax ≅ 670 nm; ε = 1700 M-1 cm-1), respectively. Upon warming to room temperature, the solutions turn yellow, ultimately converting to isolable diiron(III) compounds [Fe2(μ-OH)2(μ-02CArTol) 2(O2CArTol)2L2] (L = C5H5N (1c), 4-tBuC5H4N (2c)). EPR and Mössbauer spectroscopic studies revealed the presence of equimolar amounts of valence-delocalized FeIIFeIII and valence-trapped FeIIIFeIV species as major components of solution 2b. The spectroscopic and reactivity properties of the FeIIIFeIV species are similar to those of the intermediate X in the RNR-R2 catalytic cycle. EPR kinetic studies revealed that the processes leading to the formation of these two distinctive paramagnetic components are coupled to one another. A mechanism for this reaction is proposed and compared with those of other synthetic and biological systems, in which electron transfer occurs from a low-valent starting material to putative high-valent dioxygen adduct(s).

Original languageEnglish (US)
Pages (from-to)3993-4007
Number of pages15
JournalJournal of the American Chemical Society
Volume124
Issue number15
DOIs
StatePublished - Apr 17 2002

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Paramagnetic resonance
Enzymes
Oxygen
Benzoates
Biological systems
Electrons
Kinetics
Temperature

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

@article{201a82011ce64486b761591a7fb4e3ef,
title = "Functional mimic of dioxygen-activating centers in non-heme diiron enzymes: Mechanistic implications of paramagnetic intermediates in the reactions between diiron(II) complexes and dioxygen",
abstract = "Two tetracarboxylate diiron(II) complexes, [Fe2(μ-O2CArTol)2 (O2CArTol)2 (C5H5N)2] (1a) and [Fe2μ-O2CArTol)4 (4-tBuC5H4N)2] (2a), where ArTolCO2- = 2,6-di(p-tolyl)benzoate, react with 02 in CH2Cl2 at -78°C to afford dark green intermediates 1b (λmax ≅ 660 nm; ε = 1600 M-1 cm-1) and 2b λmax ≅ 670 nm; ε = 1700 M-1 cm-1), respectively. Upon warming to room temperature, the solutions turn yellow, ultimately converting to isolable diiron(III) compounds [Fe2(μ-OH)2(μ-02CArTol) 2(O2CArTol)2L2] (L = C5H5N (1c), 4-tBuC5H4N (2c)). EPR and M{\"o}ssbauer spectroscopic studies revealed the presence of equimolar amounts of valence-delocalized FeIIFeIII and valence-trapped FeIIIFeIV species as major components of solution 2b. The spectroscopic and reactivity properties of the FeIIIFeIV species are similar to those of the intermediate X in the RNR-R2 catalytic cycle. EPR kinetic studies revealed that the processes leading to the formation of these two distinctive paramagnetic components are coupled to one another. A mechanism for this reaction is proposed and compared with those of other synthetic and biological systems, in which electron transfer occurs from a low-valent starting material to putative high-valent dioxygen adduct(s).",
author = "Dongwhan Lee and Brad Pierce and Carsten Krebs and Hendrich, {Michael P.} and Huynh, {Boi Hanh} and Lippard, {Stephen J.}",
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Functional mimic of dioxygen-activating centers in non-heme diiron enzymes : Mechanistic implications of paramagnetic intermediates in the reactions between diiron(II) complexes and dioxygen. / Lee, Dongwhan; Pierce, Brad; Krebs, Carsten; Hendrich, Michael P.; Huynh, Boi Hanh; Lippard, Stephen J.

In: Journal of the American Chemical Society, Vol. 124, No. 15, 17.04.2002, p. 3993-4007.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Functional mimic of dioxygen-activating centers in non-heme diiron enzymes

T2 - Mechanistic implications of paramagnetic intermediates in the reactions between diiron(II) complexes and dioxygen

AU - Lee, Dongwhan

AU - Pierce, Brad

AU - Krebs, Carsten

AU - Hendrich, Michael P.

AU - Huynh, Boi Hanh

AU - Lippard, Stephen J.

PY - 2002/4/17

Y1 - 2002/4/17

N2 - Two tetracarboxylate diiron(II) complexes, [Fe2(μ-O2CArTol)2 (O2CArTol)2 (C5H5N)2] (1a) and [Fe2μ-O2CArTol)4 (4-tBuC5H4N)2] (2a), where ArTolCO2- = 2,6-di(p-tolyl)benzoate, react with 02 in CH2Cl2 at -78°C to afford dark green intermediates 1b (λmax ≅ 660 nm; ε = 1600 M-1 cm-1) and 2b λmax ≅ 670 nm; ε = 1700 M-1 cm-1), respectively. Upon warming to room temperature, the solutions turn yellow, ultimately converting to isolable diiron(III) compounds [Fe2(μ-OH)2(μ-02CArTol) 2(O2CArTol)2L2] (L = C5H5N (1c), 4-tBuC5H4N (2c)). EPR and Mössbauer spectroscopic studies revealed the presence of equimolar amounts of valence-delocalized FeIIFeIII and valence-trapped FeIIIFeIV species as major components of solution 2b. The spectroscopic and reactivity properties of the FeIIIFeIV species are similar to those of the intermediate X in the RNR-R2 catalytic cycle. EPR kinetic studies revealed that the processes leading to the formation of these two distinctive paramagnetic components are coupled to one another. A mechanism for this reaction is proposed and compared with those of other synthetic and biological systems, in which electron transfer occurs from a low-valent starting material to putative high-valent dioxygen adduct(s).

AB - Two tetracarboxylate diiron(II) complexes, [Fe2(μ-O2CArTol)2 (O2CArTol)2 (C5H5N)2] (1a) and [Fe2μ-O2CArTol)4 (4-tBuC5H4N)2] (2a), where ArTolCO2- = 2,6-di(p-tolyl)benzoate, react with 02 in CH2Cl2 at -78°C to afford dark green intermediates 1b (λmax ≅ 660 nm; ε = 1600 M-1 cm-1) and 2b λmax ≅ 670 nm; ε = 1700 M-1 cm-1), respectively. Upon warming to room temperature, the solutions turn yellow, ultimately converting to isolable diiron(III) compounds [Fe2(μ-OH)2(μ-02CArTol) 2(O2CArTol)2L2] (L = C5H5N (1c), 4-tBuC5H4N (2c)). EPR and Mössbauer spectroscopic studies revealed the presence of equimolar amounts of valence-delocalized FeIIFeIII and valence-trapped FeIIIFeIV species as major components of solution 2b. The spectroscopic and reactivity properties of the FeIIIFeIV species are similar to those of the intermediate X in the RNR-R2 catalytic cycle. EPR kinetic studies revealed that the processes leading to the formation of these two distinctive paramagnetic components are coupled to one another. A mechanism for this reaction is proposed and compared with those of other synthetic and biological systems, in which electron transfer occurs from a low-valent starting material to putative high-valent dioxygen adduct(s).

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