Fe(III) complexes of 1,4,8,11-tetraaza[14]annulenes as catalase mimics.
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.
Sustmann
Reiner
R
Institut für Organische Chemie, Universität Duisburg-Essen, 45117, Essen, Germany. reiner.sustmann@uni-duisburg-essen.de
Korth
Hans-Gert
HG
Kobus
Diana
D
Baute
Jörg
J
Seiffert
Karl-Heinz
KH
Verheggen
Elisabeth
E
Bill
Eckhard
E
Kirsch
Michael
M
de Groot
Herbert
H
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
D001372:Aza Compounds; D005290:Ferric Compounds; D008024:Ligands; D011083:Polycyclic Compounds; D006861:Hydrogen Peroxide; D002374:Catalase; D010100:Oxygen