Biomimetic oxidation of 3,5-di-tert-butylcatechol by dioxygen via Mn-enhanced base catalysis

Imola Cs Szigyártó, László I. Simándi, L. Párkányí, L. Korecz, G. Schlosser

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Abstract

The 6-coordinate dioximatomanganese(II) complex [Mn(HL)(CH 3OH)]+ (2, where H2L is [HON=C(CH 3)C(CH3)=NCH2-CH2]2NH), formed by instant solvolysis of [Mn2(HL)2](BPh 4)2 (1) in methanol, accelerates the triethylamine (TEA)-catalyzed oxidation of 3,5-di-tert-butylcatechol (H2dtbc) by O2 to the corresponding o-benzoquinone. Significantly, 2 alone has no catalytic effect. The observed rate increase can be explained by the interaction of 2 with the hydroperoxo intermediate HdtbcO2 - formed from Hdtbc- and O2 in the TEA-catalyzed oxidation. The kinetics of the TEA-catalyzed and Mn-enhanced reaction has been studied by gas-volumetric monitoring of the amount of O 2 consumed. The initial rate of O2 uptake (Vin) shows a first-order dependence on the concentration of 2 and O2 and saturation kinetics with respect to both H2dtbc and TEA. The observed kinetic behavior is consistent with parallel TEA-catalyzed and Mn-enhanced oxidation paths. The 3,5-di-tert-butylsemiquinone anion radical is an intermediate detectable by electron spin resonance (ESR) spectroscopy. The dimeric catalyst precursor has been characterized by X-ray diffraction and electrospray ionization mass spectrometry and the monomeric catalyst by ESR spectroscopy.

Original languageEnglish
Pages (from-to)7480-7487
Number of pages8
JournalInorganic Chemistry
Volume45
Issue number18
DOIs
Publication statusPublished - Sep 4 2006

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biomimetics
Biomimetics
Catalysis
catalysis
Oxygen
Oxidation
oxidation
electron paramagnetic resonance
Electron spin resonance spectroscopy
kinetics
methylidyne
solvolysis
catalysts
Kinetics
quinones
spectroscopy
mass spectroscopy
methyl alcohol
Electrospray ionization
Catalysts

ASJC Scopus subject areas

  • Inorganic Chemistry

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Biomimetic oxidation of 3,5-di-tert-butylcatechol by dioxygen via Mn-enhanced base catalysis. / Szigyártó, Imola Cs; Simándi, László I.; Párkányí, L.; Korecz, L.; Schlosser, G.

In: Inorganic Chemistry, Vol. 45, No. 18, 04.09.2006, p. 7480-7487.

Research output: Contribution to journalArticle

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AU - Schlosser, G.

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AB - The 6-coordinate dioximatomanganese(II) complex [Mn(HL)(CH 3OH)]+ (2, where H2L is [HON=C(CH 3)C(CH3)=NCH2-CH2]2NH), formed by instant solvolysis of [Mn2(HL)2](BPh 4)2 (1) in methanol, accelerates the triethylamine (TEA)-catalyzed oxidation of 3,5-di-tert-butylcatechol (H2dtbc) by O2 to the corresponding o-benzoquinone. Significantly, 2 alone has no catalytic effect. The observed rate increase can be explained by the interaction of 2 with the hydroperoxo intermediate HdtbcO2 - formed from Hdtbc- and O2 in the TEA-catalyzed oxidation. The kinetics of the TEA-catalyzed and Mn-enhanced reaction has been studied by gas-volumetric monitoring of the amount of O 2 consumed. The initial rate of O2 uptake (Vin) shows a first-order dependence on the concentration of 2 and O2 and saturation kinetics with respect to both H2dtbc and TEA. The observed kinetic behavior is consistent with parallel TEA-catalyzed and Mn-enhanced oxidation paths. The 3,5-di-tert-butylsemiquinone anion radical is an intermediate detectable by electron spin resonance (ESR) spectroscopy. The dimeric catalyst precursor has been characterized by X-ray diffraction and electrospray ionization mass spectrometry and the monomeric catalyst by ESR spectroscopy.

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