Synthesis, characterization and magnetic studies of oxamido-bridged copper(II)-iron(III) heterobinuclear complexes

Two new oxamido-bridged Cu(II)-Fe(III) heterobinuclear complexes of formulae [Cu(dmoxpn)Fe(bpy)(2)](ClO4)(3) (1) and [Cu(dmoxae)Fc(bpy)(2)](ClO4)(3) (2) have been synthesized, where bpy denotes 2,2'-bipyridine; while dmoxpn and dmoxae represent N,N'-bis[3-(dimethylamino)propyl]oxamido and N,N'-bis[2-(dimethylamino)ethyl]oxamido dianions, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectral studies, it is proposed that the two complexes have oxamido-bridged structures consisting of a copper(II) and an iron(III) ions, which have a square planar environment and a distorted octahedral environment, respectively. The two heterobinuclear complexes were further characterized by variable-temperature magnetic susceptibility (4:2 similar to 300 K) measurements and the observed data were simulated by the equation based on the spin Hamiltonian operator (H) over cap = -2J (S) over cap (.)(1)(S) over cap (2), giving the exchange integral J = -18.2 cm(-1) for (1) and J = -26.5 cm(-1) for (2). The results revealed the occurrence of an intramolecular antiferromagnetic interaction between the adjacent iron(III) and copper(II) ions through the oxamido-bridge within each molecule. The influence of the chelate ring arrangement around the copper(II) in the copper(II)-iron(III) heterobinuclear complexes on magnetic interactions between the metal ions of this kind of complexes is preliminarily discussed.