title: Insertion of a hydroxido bridge into a diphenoxido dinuclear copper(II) complex: drastic change of the magnetic property from strong antiferromagnetic to ferromagnetic and enhancement in the catecholase activity.
abstract: A diphenoxido-bridged dinuclear copper(II) complex, [Cu(2)L(2)(ClO(4))(2)] (1), has been synthesized using a tridentate reduced Schiff base ligand, 2-[[2-(diethylamino)ethylamino]methyl]phenol (HL). The addition of triethylamine to the methanolic solution of this complex produced a novel triple bridged (double phenoxido and single hydroxido) dinuclear copper(II) complex, [Cu(2)L(2)(OH)]ClO(4) (2). Both complexes 1 and 2 were characterized by X-ray structural analyses, variable-temperature magnetic susceptibility measurements, and spectroscopic methods. In 1, the two phenoxido bridges are equatorial-equatorial and the species shows strong antiferromagnetic coupling with J = -615.6(6.1) cm(-1). The inclusion of the equatorial-equatorial hydroxido bridge in 2 changes the Cu···Cu distance from 3.018 Å (avg.) to 2.798 Å (avg.), the positions of the phenoxido bridges to axial-equatorial, and the magnetic coupling to ferromagnetic with J = 50.1(1.4) cm(-1). Using 3,5-di-tert-butylcatechol as the substrate, the catecholase activity of the complexes has been studied in a methanol solution; compound 2 shows higher catecholase activity (k(cat) = 233.4 h(-1)) than compound 1 (k(cat) = 93.6 h(-1)). Both complexes generate identical species in solution, and they are interconvertible simply by changing the pH of their solutions. The higher catecholase activity of 2 seems to be due to the presence of the OH group, which increases the pH of its solution.
authors.affiliation: Department of Chemistry, University College of Science, University of Calcutta, 92 APC Road, Kolkata 700 009, India.
authors.forename: Apurba
authors.initials: A
authors.lastname: Biswas
authors.forename: Lakshmi Kanta
authors.initials: LK
authors.lastname: Das
authors.forename: Michael G B
authors.initials: MG
authors.lastname: Drew
authors.forename: Carmen
authors.initials: C
authors.lastname: Diaz
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Ghosh
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry* / Q000378:metabolism; D002396:Catechols / Q000378:metabolism*; D056831:Coordination Complexes / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006878:Hydroxides / Q000737:chemistry / Q000378:metabolism; D059346:Magnets / Q000737:chemistry*; D008958:Models, Molecular; D010636:Phenols / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry
chemical_list: D002396:Catechols; D056831:Coordination Complexes; D006878:Hydroxides; D010636:Phenols; D012545:Schiff Bases; C054068:3,5-di-tert-butylcatechol; D003300:Copper; D004156:Catechol Oxidase