title: Spectroscopic and mechanistic studies on oxidation reactions catalyzed by the functional Model SR complex for cytochrome P450: influence of oxidant, substrate, and solvent.
abstract: Kinetic and mechanistic studies on the formation of an oxoiron(IV) porphyrin cation radical bearing a thiolate group as proximal ligand are reported. The SR complex, a functional enzyme mimic of P450, was oxidized in peroxo-shunt reactions under different experimental conditions with variation of solvent, temperature, and identity and excess of oxidant in the presence of different organic substrates. Through the application of a low-temperature rapid-scan stopped-flow technique, the reactive intermediates in the SR catalytic cycle, such as the initially formed SR acylperoxoiron(III) complex and the SR high-valent iron(IV) porphyrin cation radical complex [(SR(*+))Fe(IV)=O], were successfully identified and kinetically characterized. The oxidation of the SR complex under catalytic conditions provided direct spectroscopic information on the reactivity of [(SR(.+))Fe(IV)=O] towards the oxidation of selected organic substrates. Because the catalytically active species is a synthetic oxoiron(IV) porphyrin cation radical bearing a thiolate proximal group, the effect of the strong electron donor ligand on the formation and reactivity/stability of the SR high-valent iron species is addressed and discussed in the light of the reactivity pattern observed in substrate oxygenation reactions catalyzed by native P450 enzyme systems.
authors.affiliation: Inorganic Chemistry, Department of Chemistry and Pharmacy, Egerlandstrasse 1, 91058 Erlangen, Germany.
authors.forename: Natalya
authors.initials: N
authors.lastname: Hessenauer-Ilicheva
authors.forename: Alicja
authors.initials: A
authors.lastname: Franke
authors.forename: Maria
authors.initials: M
authors.lastname: Wolak
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Higuchi
authors.forename: Rudi
authors.initials: R
authors.lastname: van Eldik
mesh_terms: D002384:Catalysis; D002412:Cations / Q000737:chemistry*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008665:Metalloporphyrins / Q000737:chemistry*; D008956:Models, Chemical; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D012997:Solvents; D013059:Spectrum Analysis, Raman; D013379:Substrate Specificity
chemical_list: D002412:Cations; D008024:Ligands; D008665:Metalloporphyrins; D016877:Oxidants; D012997:Solvents; D003577:Cytochrome P-450 Enzyme System; D007501:Iron