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Observed enhancement of the reactivity of a biomimetic diiron complex by the addition of water - mechanistic insights from theoretical modeling
Stockholm University, Faculty of Science, Department of Physics. (Per E.M. Siegbahn, Margareta R.A. Blomberg)
Stockholm University, Faculty of Science, Department of Physics. (Per E.M. Siegbahn, Margareta R.A. Blomberg)
2009 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 34, p. 6741-6750Article in journal (Refereed) Published
Abstract [en]

The biomimetic diiron complex [FeIIIFeIV(m-O)2(5-Me3-TPA)2](ClO4)3 (TPA = tris(2- pyridylmethyl)amine) has been found to be capable of oxidizing 9,10-dihydroanthracene in a solution of acetonitrile. Addition of water up to 1 M makes the reaction 200 times faster, suggesting that the water molecule in some way activates the catalyst for more efficient substrate oxidation. It is proposed that the enhanced reactivity results from the coordination of a water molecule to the iron(III) half of the complex, converting the bis-m-oxo structure of the diiron complex to a ring-opened form where one of the bridging oxo groups is transformed into a terminal oxo group on iron(IV). The suggested mechanism is supported by DFT (B3LYP) calculations and transition state theory. Two different computational models of the diiron complex are used to model the hydroxylation of cyclohexane to cyclohexanol. Model 1 has a bis-m-oxo diiron core (diamond core) while model 2 represents the “open core” analogue with one bridging m-oxo group, a terminal oxo ligand on iron(IV), and a water molecule coordinated to iron(III). The computational results clearly suggest that the terminal oxo group is more reactive than the bridging oxo group. The free energy of activation is 7.0 kcal mol-1 lower for the rate limiting step when the oxidant has a terminal oxo group than when both oxo groups are bridging the irons.

Place, publisher, year, edition, pages
2009. Vol. 34, p. 6741-6750
Keywords [en]
biomimetic dft diiron reactivity enhancement
National Category
Inorganic Chemistry
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-38195ISI: 000269082100012OAI: oai:DiVA.org:su-38195DiVA, id: diva2:306949
Available from: 2010-03-31 Created: 2010-03-31 Last updated: 2022-02-24Bibliographically approved
In thesis
1. Biomimetic Iron Complexes involved in Oxygenation and Chlorination: A Theoretical Study
Open this publication in new window or tab >>Biomimetic Iron Complexes involved in Oxygenation and Chlorination: A Theoretical Study
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomimetic chemistry is directed towards the simulation of enzymatic reactivity with synthetic analogues. In this thesis a quantum chemical method has been employed to study the mechanism of highly reactive iron-oxo complexes involved in oxygenation and chlorination of organic substrates. The aim of this research is to gain greater understanding for the reactivity paradigm of the iron-oxo group.

One reaction deals with the conversion of cyclohexane into adipic acid, a key chemical in industrial chemistry, catalyzed by an iron(II)-porphyrin complex in the presence of dioxygen. This process constitutes a ’green’ alternative to conventional adipic acid production, and is thus of great interest to synthetic chemistry. Another reaction investigated herein regards the selective chlorination observed for a new group of non-heme iron enzymes. With help of theoretical modeling it was possible to propose a mechanism that explains the observed selectivity. It is furthermore demonstrated how a biomimetic iron complex simulates the enzymatic reactivity by a different mechanism.

Other topics covered in this thesis regard the structure-reactivity relationship of a binuclear iron complex and the intradiol C-C bond cleavage of catechol catalyzed by an iron(III) complex.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2010. p. a-d, viii, 75
Keywords
biomimetic, iron, density functional theory, intradiol, chlorination, adpic acid, diamond core, reactivity
National Category
Inorganic Chemistry Theoretical Chemistry
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-38197 (URN)978–91–7447–013–0 (ISBN)
Public defence
2010-04-30, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Accepted. Paper 3: Submitted.Available from: 2010-04-08 Created: 2010-03-31 Last updated: 2022-02-24Bibliographically approved

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