Dinuclear triply bridged copper(II)-carboxylato compounds with different bischelating ligands: Synthesis, crystal structure, spectroscopic and magnetic properties

Abstract

Three new triply bridged dinuclear copper(II) compounds containing carboxylato bridges, [Cu 2(μ-CH 3COO-κ- O 1, O 2) 2(μ-CH 3COO-κ- O 1)(dpyam) 2](BF 4) ( 1), [Cu 2(μ-CH 2CH 3COO-κ- O 1, O 2)(μ-OH)(μ-OH 2)(bpy) 2](ClO 4) 2 ( 2) and [Cu 2(μ-CH 3COO-κ- O 1, O 2)(μ-OH)(μ-OH 2)(phen) 2](ClO 4) 2 ( 3) (in which dpyam = di-2-pyridylamine, bpy = 2,2-bipyridine, phen = phenanthroline), have been synthesized in order to investigate the magnetic super-exchange pathway between coupled copper(II) centres. All three compounds display a distorted square-pyramidal arrangement around each copper(II) ion with a CuN 2O 3 chromophore. Compound 1 has three acetato bridges, two of which connect each square pyramid at two equatorial sites in a triatomic bridging mode and the third acetato bridge acts at the apical site in the monoatomic bridging mode. The structures of compounds 2 and 3 are mutually similar. In each dinuclear unit, both copper(II) ions are linked at two equatorial positions through a hydroxo bridge and a triatomic carboxylato bridge and at the axial position through a water molecule. The magnetic susceptibility measurements, measured from 5 to 300 K, revealed an antiferromagnetic interaction between the Cu(II) ions in compound 1 and a ferromagnetic interaction for compounds 2 and 3 with singlet–triplet energy gaps ( J) of −56, 149 and 120 cm −1, for compounds 1, 2 and 3, respectively.