title: Synthesis, magnetostructural correlation, and catalytic promiscuity of unsymmetric dinuclear copper(II) complexes: models for catechol oxidases and hydrolases.
abstract: Herein, we report the synthesis and characterization, through elemental analysis, electronic spectroscopy, electrochemistry, potentiometric titration, electron paramagnetic resonance, and magnetochemistry, of two dinuclear copper(II) complexes, using the unsymmetrical ligands N',N',N-tris(2-pyridylmethyl)-N-(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L1) and N',N'-bis(2-pyridylmethyl)-N,N-(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L2). The structures of the complexes [Cu(2)(L1)(μ-OAc)](ClO(4))(2)·(CH(3))(2)CHOH (1) and [Cu(2)(L2)(μ-OAc)](ClO(4))·H(2)O·(CH(3))(2)CHOH (2) were determined by X-ray crystallography. The complex [Cu(2)(L3)(μ-OAc)](2+) [3; L3 = N-(2-hydroxybenzyl)-N',N',N-tris(2-pyridylmethyl)-1,3-propanediamin-2-ol] was included in this study for comparison purposes only (Neves et al. Inorg. Chim. Acta2005, 358, 1807-1822). Magnetic data show that the Cu(II) centers in 1 and 2 are antiferromagnetically coupled and that the difference in the exchange coupling J found for these complexes (J = -4.3 cm(-1) for 1 and J = -40.0 cm(-1) for 2) is a function of the Cu-O-Cu bridging angle. In addition, 1 and 2 were tested as catalysts in the oxidation of the model substrate 3,5-di-tert-butylcatechol and can be considered as functional models for catechol oxidase. Because these complexes possess labile sites in their structures and in solution they have a potential nucleophile constituted by a terminal Cu(II)-bound hydroxo group, their activity toward hydrolysis of the model substrate 2,4-bis(dinitrophenyl)phosphate and DNA was also investigated. Double electrophilic activation of the phosphodiester by monodentate coordination to the Cu(II) center that contains the phenol group with tert-butyl substituents and hydrogen bonding of the protonated phenol with the phosphate O atom are proposed to increase the hydrolase activity (K(ass.) and k(cat.)) of 1 and 2 in comparison with that found for complex 3. In fact, complexes 1 and 2 show both oxidoreductase and hydrolase/nuclease activities and can thus be regarded as man-made models for studying catalytic promiscuity.
authors.affiliation: Laboratório de Bioinorgânica e Crystalografia (LABINC), Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina, Brazil.
authors.forename: Renata E H M B
authors.initials: RE
authors.lastname: Osório
authors.forename: Rosely A
authors.initials: RA
authors.lastname: Peralta
authors.forename: Adailton J
authors.initials: AJ
authors.lastname: Bortoluzzi
authors.forename: Vicente R
authors.initials: VR
authors.lastname: de Almeida
authors.forename: Bruno
authors.initials: B
authors.lastname: Szpoganicz
authors.forename: Franciele L
authors.initials: FL
authors.lastname: Fischer
authors.forename: Hernán
authors.initials: H
authors.lastname: Terenzi
authors.forename: Antonio S
authors.initials: AS
authors.lastname: Mangrich
authors.forename: Karen Mary
authors.initials: KM
authors.lastname: Mantovani
authors.forename: Dalva E C
authors.initials: DE
authors.lastname: Ferreira
authors.forename: Willian R
authors.initials: WR
authors.lastname: Rocha
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Haase
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Tomkowicz
authors.forename: Ademir
authors.initials: A
authors.lastname: dos Anjos
authors.forename: Ademir
authors.initials: A
authors.lastname: Neves
mesh_terms: D002384:Catalysis; D004156:Catechol Oxidase / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006867:Hydrolases / Q000737:chemistry*; D008958:Models, Molecular; D013055:Spectrophotometry, Infrared
chemical_list: D003300:Copper; D004156:Catechol Oxidase; D006867:Hydrolases