A Tetracopper(II)-Tetraradical Cuboidal Core and Its Reactivity as a Functional Model of Phenoxazinone Synthase

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• 作者：Chandan Mukherjee ; Thomas Weyhermü ; ller ; Eberhard Bothe ; Eva Rentschler ; Phalguni Chaudhuri
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：November 12, 2007
• 年：2007
• 卷：46
• 期：23
• 页码：9895 - 9905
• 全文大小：257K
• 年卷期：v.46,no.23(November 12, 2007)
• ISSN：1520-510X

文摘

The coordination chemistry of the tridentate ligand N-(2-hydroxy-3,5-di-tert-butylphenyl)-2-aminobenzylalcohol H₃Lhas been studied with the copper(II) ion. The ligand is noninnocent in the sense that it is readily oxidized in thepresence of air to its o-iminobenzosemiquinonato [L]^2- radical form. The crystal structure of the synthesizedtetracopper(II)-tetraradical complex [Cu^II₄(L)₄] (1), has been determined by X-ray crystallography at 100 K. Variable-temperature (2-290 K) magnetic susceptibility measurements of complex 1 containing eight paramagnetic centersestablish the spin ground state to be diamagnetic (S_t = 0) arising from the antiferromagnetic interactions.Electrochemical measurements (cyclic voltammograms and square wave voltammograms) indicate four one-electronreductions of the ligand prior to the reduction of the metal center. Complex 1 is found to catalyze the aerialoxidation of 2-aminophenol to 2-amino-phenoxazine-3-one, thus modeling the catalytic function of the copper-containing enzyme phenoxazinone synthase. Kinetic measurements together with electron paramagnetic resonanceand electronic spectral studies have been used to decipher the complex six-electron oxidative coupling of2-aminophenol. An "on-off" mechanism of the radicals together with redox participation of the metal center isproposed for the catalytic oxidation processes.