FeIII Complexes of 1,4,8,11-Tetraaza[14]annulenes as Catalase Mimics

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• 作者：Reiner Sustmann ; Hans-Gert Korth ; Diana Kobus ; J&ouml ; rg Baute ; Karl-Heinz Seiffert ; Elisabeth Verheggen ; Eckhard Bill ; Michael Kirsch ; Herbert de Groot
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：December 24, 2007
• 年：2007
• 卷：46
• 期：26
• 页码：11416 - 11430
• 全文大小：193K
• 年卷期：v.46,no.26(December 24, 2007)
• ISSN：1520-510X

文摘

The development of enzyme mimics of catalase which decompose hydrogen peroxide to water and molecularoxygen according to the 2:1 stoichiometry of native catalase and in aqueous solution at pH 7 and at micromolarconcentrations of the enzyme model and hydrogen peroxide is reported. For this purpose, iron(III) complexes of1,4,8,11-tetraaza[14]annulenes are prepared by various procedures. Efficacious preparations utilize reaction of the[N₄] macrocyles with Fe^II salts in the presence of triphenylamine, followed by gentle oxidation of the Fe^II complexesby molecular oxygen or by tris(4-bromophenyl)aminium hexachloroantimonate. The complexes are characterizedby SQUID magnetometry and by Mössbauer, EPR, and UV/vis spectrometry. In the solid state, the iron(III) centerof the catalytically active complexes exists in the intermediate (quartet, S = ³/₂) spin state. Several of these complexesdecompose hydrogen peroxide in aqueous buffer solution at pH 7.2 at room temperature with turnover numbersbetween 40 and 80. The apparent second-order rate constant for hydrogen peroxide decomposition is in the rangeof 1400-2400 M^-1s^-1, about 3 orders of magnitude lower than the value for native catalase. Besides oxygenproduction, a non-oxygen releasing pathway of hydrogen peroxide decomposition is unveiled.