title: Mechanistic insight on the catecholase activity of dinuclear copper complexes with distant metal centers.
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, [Cu(2)(diep)(H(2)O)(4)](ClO(4))(4)·2H(2)O, 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 MeOH-H(2)O 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.
authors.affiliation: Departamento de Química Inorgánica y Nuclear, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF 04510, Mexico.
authors.forename: María Rosa
authors.initials: MR
authors.lastname: Mendoza-Quijano
authors.forename: Gerardo
authors.initials: G
authors.lastname: Ferrer-Sueta
authors.forename: Marcos
authors.initials: M
authors.lastname: Flores-Álamo
authors.forename: Núria
authors.initials: N
authors.lastname: Aliaga-Alcalde
authors.forename: Virginia
authors.initials: V
authors.lastname: Gómez-Vidales
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Ugalde-Saldívar
authors.forename: Laura
authors.initials: L
authors.lastname: Gasque
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D008280:Magnetics; D010084:Oxidation-Reduction
chemical_list: D002396:Catechols; D056831:Coordination Complexes; C054068:3,5-di-tert-butylcatechol; D003300:Copper; D004156:Catechol Oxidase