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

Three new triply bridged dinuclear copper(II) compounds containing carboxylato bridges, [Cu2(μ-CH3COO-κ-O1,O2)2(μ-CH3COO-κ-O1)(dpyam)2](BF4) (1), [Cu2(μ-CH2CH3COO-κ-O1,O2)(μ-OH)(μ-OH2)(bpy)2](ClO4)2 (2) and [Cu2(μ-CH3COO-κ-O1,O2)(μ-OH)(μ-OH2)(phen)2](ClO4)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 CuN2O3 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.