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The Conversion of Cyclohexane to Adipic Acid catalyzed by an Iron-Porphirin Complex. A theoretical study
Stockholm University, Faculty of Science, Department of Physics. (Theoretical Biochemistry)
Stockholm University, Faculty of Science, Department of Physics. (Theoretical Biochemistry)
Department fur Chemie, Universität in Aachen.
Stockholm University, Faculty of Science, Department of Physics. (Theoretical Biochemistry)
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(English)Manuscript (preprint) (Other academic)
Keyword [en]
biomimetic complexes, adipic acid, heme, density functional calculations, spin transition, catalysis
National Category
Natural Sciences
Research subject
URN: urn:nbn:se:su:diva-30782OAI: diva2:274030
Available from: 2009-10-26 Created: 2009-10-26 Last updated: 2010-04-01Bibliographically approved
In thesis
1. Reaction Mechanisms of Metalloenzymes and Synthetic Model Complexes Activating Dioxygen: A Computational study
Open this publication in new window or tab >>Reaction Mechanisms of Metalloenzymes and Synthetic Model Complexes Activating Dioxygen: A Computational study
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantum chemistry has nowadays become a powerful and efficient tool that can be successfully used for studies of biosystems. It is therefore possibleto model the enzyme active-site and the reactions undergoing into it, as well as obtaining quite accurate energetic profiles. Important conclusions can be drawn from such profiles about the  plausibility of different putative mechanisms.

Density Functional Theory is used in the present thesis for investigation of the catalytic mechanism of dioxygenase metallo-enzymes and synthetic model complexes. Three enzymes were studied – Homoprotocatechuate 2,3-dioxygenase isolated from Brevibacterium fuscum (Bf 2,3-HPCD), Manganese-Dependent Homoprotocatechuate 2,3-Dioxygenase (MndD) and Homogentisate Dioxygenase (HGD). Models consisting of 55 to 208 atoms have been built from X-ray crystal structures and used in the calculations. The computed energies were put in energy curves and were used for estimation of the feasibility of the suggested reaction mechanisms. A non-heme [(L4Me4)Fe(III)]+3 complex that mimics the reactivity of intradiol dioxygenases, and a heme [T(o-Cl)PPFe] complex catalyzing the stepwise oxidation of cyclohexane to adipic acid, were also studied.

For the enzymes and the non-heme biomimetic complex the reaction was found to follow a mechanism that was previously suggested for extradiol and intradiol dioxygenases – ordered substrates binding and formation of peroxo species, which further undergoes homolytic O-O bond cleavage. Different reaction steps appear to be rate limiting in the particular cases: proton transfer from the substrate to the peroxide in Bf 2,3-HPCD, the formation of the peroxo bridge in HGD and the biomimetic complex, and notably, spin transition in MndD.

The catalytic oxidation of cyclohexane to adipic acid in the presence of molecular oxygen as oxidant was studied, a reaction of great importance for the chemical industry. Reaction mechanism is suggested, involving several consecutive oxidative steps. The highest calculated enthalpy of activation is 17.8 kcal/mol for the second oxidative step.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2009. 104 p.
catalysis, density functional theory, extradiol, intradiol, dioxygenases, oxygen, biomimetic complexes, heme, spin transition, adipic acid
National Category
Atom and Molecular Physics and Optics
Research subject
Quantum Chemistry
urn:nbn:se:su:diva-30706 (URN)978-91-7155-965-4 (ISBN)
Public defence
2009-11-20, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, Sweden, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In progress, Paper 5: In progressAvailable from: 2009-10-28 Created: 2009-10-23 Last updated: 2010-04-09Bibliographically approved

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Noack, HolgerGeorgiev, ValentinBlomberg, Margareta R.A.Siegbahn, Per E.M.
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