title: Fe(III) complexes of 1,4,8,11-tetraaza[14]annulenes as catalase mimics.
abstract: The development of enzyme mimics of catalase which decompose hydrogen peroxide to water and molecular oxygen according to the 2:1 stoichiometry of native catalase and in aqueous solution at pH 7 and at micromolar concentrations of the enzyme model and hydrogen peroxide is reported. For this purpose, iron(III) complexes of 1,4,8,11-tetraaza[14]annulenes are prepared by various procedures. Efficacious preparations utilize reaction of the [N4] macrocyles with FeII salts in the presence of triphenylamine, followed by gentle oxidation of the FeII complexes by molecular oxygen or by tris(4-bromophenyl)aminium hexachloroantimonate. The complexes are characterized by SQUID magnetometry and by Mössbauer, EPR, and UV/vis spectrometry. In the solid state, the iron(III) center of the catalytically active complexes exists in the intermediate (quartet, S = 3/2) spin state. Several of these complexes decompose hydrogen peroxide in aqueous buffer solution at pH 7.2 at room temperature with turnover numbers between 40 and 80. The apparent second-order rate constant for hydrogen peroxide decomposition is in the range of 1400-2400 M(-1) s(-1), about 3 orders of magnitude lower than the value for native catalase. Besides oxygen production, a non-oxygen releasing pathway of hydrogen peroxide decomposition is unveiled.
authors.affiliation: Institut für Organische Chemie, Universität Duisburg-Essen, 45117, Essen, Germany. reiner.sustmann@uni-duisburg-essen.de
authors.forename: Reiner
authors.initials: R
authors.lastname: Sustmann
authors.forename: Hans-Gert
authors.initials: HG
authors.lastname: Korth
authors.forename: Diana
authors.initials: D
authors.lastname: Kobus
authors.forename: Jörg
authors.initials: J
authors.lastname: Baute
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Seiffert
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Verheggen
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Michael
authors.initials: M
authors.lastname: Kirsch
authors.forename: Herbert
authors.initials: H
authors.lastname: de Groot
mesh_terms: D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism*; D004583:Electrons; D005290:Ferric Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D011083:Polycyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D001372:Aza Compounds; D005290:Ferric Compounds; D008024:Ligands; D011083:Polycyclic Compounds; D006861:Hydrogen Peroxide; D002374:Catalase; D010100:Oxygen