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Mechanistic insight into formation of oxo-iron (IV) porphyrin pi -cation radicals from enzyme mimics of cytochrome P450 in organic solvents

Hessenauer-Ilicheva, Natalya and Franke, Alicja and Meyer, Dominik and Woggon, Wolf-D. and van Eldik, Rudi. (2009) Mechanistic insight into formation of oxo-iron (IV) porphyrin pi -cation radicals from enzyme mimics of cytochrome P450 in organic solvents. Chemistry, Vol. 15, H. 12. pp. 2941-2959.

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Official URL: http://edoc.unibas.ch/dok/A5260119

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Abstract

Two new models for cytochrome P 450 in which the thiolate axial ligand is replaced by a RSO3- group, form oxo-iron (IV) porphyrin pi-cation radicals as sole oxidn. products in "peroxo shunt" reactions independent of the nature of the employed solvent (polar or non-polar) and electronic nature of the porphyrin rings.  Although the properties of the solvent and push-pull effects from the porphyrin rings do not affect the mode of the O-O bond cleavage (heterolytic or homolytic) in these models, they strongly affect the rate and mechanism of each reaction step leading to the formation of the high-valent iron intermediates.  This article reports the results of mechanistic studies involving the measurements of the rate of oxo-iron (IV) porphyrin pi-cation radical formation from the enzyme mimics of P 450 for different oxidant concn., temp. and pressure in selected org. solvents.  Extn. of the appropriate rate consts. and activation parameters for the reactions studied enable a detailed discussion of the effects of solvent and electronic nature of the porphyrin rings on the position of the first pre-equil. involving formation of the acylperoxo-iron (III) porphyrin intermediate, as well as on the rate of heterolytic O-O bond cleavage leading to the formation of the high-valent iron species.  Furthermore, an unusual effect of solvent on the kinetics of oxo-iron (IV) porphyrin pi-cation radical formation in methanol is demonstrated and discussed in the present work.
Faculties and Departments:05 Faculty of Science
05 Faculty of Science > Departement Chemie > Chemie
UniBasel Contributors:Woggon, Wolf-Dietrich
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Wiley-VCH Verlag
ISSN:0947-6539
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:25
Deposited On:22 Mar 2012 13:43

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