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Issue 16, 2012
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Mechanistic insight on the catecholase activity of dinuclear copper complexes with distant metal centers

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Abstract

The catecholase activity of two dinuclear Cu(II) complexes with distant metal centers is discussed together with solid state and solution studies. The crystal structure for one of them, [Cu2(diep)(H2O)4](ClO4)4·2H2O, is described, showing the two copper ions are 7.457 Å apart and in a square pyramidal coordination. Both complexes display a weak antiferromagnetic coupling in the solid state that is manifest in the dimer EPR spectra obtained in frozen solution. The pH-potentiometric speciation performed in 1 : 1 MeOHH2O allowed the assignment of hydrolyzed copper species as those catalytically active in the oxidation of 3,5-di-tert-butylcatechol (DTBC). The kinetic measurements led us to propose behavior consistent with Michaelis–Menten plus a linear dependence of the initial rate on [DTBC]. This can be associated with the presence of more than one catalytically active species, which is consistent with the evidence of several differently hydrolyzed species shown in the predominance diagrams. Product characterization studies led to establishing the formation of hydrogen peroxide during the catalytic cycle, while semiquinone and superoxide radicals were detected by EPR spectroscopy, supporting one-electron transference at each of the copper centers.

Graphical abstract: Mechanistic insight on the catecholase activity of dinuclear copper complexes with distant metal centers

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Publication details

The article was received on 11 Nov 2011, accepted on 09 Feb 2012 and first published on 12 Mar 2012


Article type: Paper
DOI: 10.1039/C2DT12155G
Citation: Dalton Trans., 2012,41, 4985-4997
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    Mechanistic insight on the catecholase activity of dinuclear copper complexes with distant metal centers

    M. R. Mendoza-Quijano, G. Ferrer-Sueta, M. Flores-Álamo, N. Aliaga-Alcalde, V. Gómez-Vidales, V. M. Ugalde-Saldívar and L. Gasque, Dalton Trans., 2012, 41, 4985
    DOI: 10.1039/C2DT12155G

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