Syntheses, crystal structures and magnetic properties of two halogen bridged dinuclear copper(II) complexes [(4,4′-diethylester-2,2′-biquinoline)2Cu2(μ-X)2X2] (X− = Cl−, Br−)

Abstract

Two dinuclear Cu2+ complexes, [(deebq)2Cu2(μ-X)2X2] (deebq=4,4′-diethylester-2,2′-biquinoline, X−=Cl− for 1 and Br− for 2), were prepared and structurally characterized. The isostructural 1 and 2 crystallize in monoclinic space group P21/c, with quite similar unit cell parameters and packing structures. Two Cu2+ ions related to each other via an inversion center are connected by two halogen anions in a μ2-bridge mode, and each Cu2+ ion is coordinated by two N atoms form one deebq ligand and three X− anions to form distorted trigonal bipyramidal coordination geometry in dinuclear Cu2+ complex. The neighboring dinuclear units are held together through intermolecular van der Waals forces. Two complexes show antiferromagnetic (AFM) coupling nature with J/kB=−73.4K for 1 and −83.7K for 2 within the dinuclear unit. The theoretical analyses utilizing broken-symmetry approach disclosed that the AFM coupling is achieved via orbital overlap in the dinuclear unit for two complexes.