Ferromagnetic exchange coupling in a new bis(μ-chloro)-bridged copper(II) Schiff base complex: Synthesis, structure, magnetic properties and catalytic oxidation of cycloalkanes

A new (mu-chloro)-bridged complex [Cu(HL)Cl](2) center dot H2O (1) with the Schiff base ligand H2L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV-Vis and EPR spectroscopic studies. X-ray diffraction studies show that 1 is a binuclear Cu-II complex with a pair of chlorine atoms bridging the copper atoms in a central Cu2Cl2 core. Each copper atom in I adopts a distorted square-pyramidal geometry with the imine nitrogen atom, alkoxy and phenoxy oxygen atoms from the Schiff base ligand and a bridging chlorine atom constructing the basal plane, while the apical position of the pyramid is occupied by the other bridging chlorine atom. Variable temperature susceptibility measurements show that complex I presents the highest ferromagnetic coupling [J = +43.2(5) cm(-1)] reported till date in any doubly chloro-bridged Cu-II dimer, and a weak interdimer antiferromagnetic coupling [J' = -0.276(8) cm(-1)]. The complex also exhibits high catalytic activity towards the oxidation of hydrocarbons using H2O2 as terminal oxidant. (C) 2009 Elsevier Ltd. All rights reserved.