Synthesis and magnetic studies of copper(II)-iron(II) heterodinuclear complexes with N,N′-bis[2-(dimethylamino)ethyl]oxamido dianion as ligand

Three new copper(II)-iron(II) heterodinuclear complexes bridged by the dianions of N,N'-bis[2-(dimethylamino)ethyl]oxamido (dmoxae) and end-capped with 2,2'-bipyridine (bpy); 1,10-phenanthroline (phen) or 5 -nitro-1,10-phenanthroline (NO(2)phen); namely [Cu(dmoxae)Fe(bpy)(2)]SO4 (1), [Cu(dmoxae)Fe(phen)(2)]SO4 (2) and [Cu(dmoxae)Fe(NO(2)phen)(2)]SO4 (3), have been synthesized and characterized. The three dinuclear complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, IR and electronic spectra studies, magnetic moments at room-temperature and molar conductivity measurements, these complexes are proposed to have an extended oxamido-bridged structure consisting of planar copper(H) and octahedral iron(II) ions. The [Cu(dmoxae)Fe(bpy)(2)]SO4 (1) and [Cu(dmoxae)Fe(phen)2]SO4 (2) complexes have been further characterized by variable temperature magnetic susceptibility (4.2similar to300 K) and the observed data were least-squares fitted to the susceptibility equation derived from the spin Hamiltonian including single-ion zero-field interaction for the iron(II) ion, (H) over cap = -2J (S) over cap (1).(S) over cap (2) - D (S) over cap (2)(Z1), giving the exchange integrals J = -20.9 cm(-1) for (1) and J = -22.7 cm(-1) for (2). These results indicated that the spin coupling between the adjacent copper(II) and iron(II) ions through the oxamido-bridge in both complexes (1) and (2) is antiferromagnetic. The influence of methyl substituents in the amine groups of the bridging ligand and the relative stability of the chelate ring arrangement around the copper(H) on magnetic interactions between the metal ions of this kind of complexes is also discussed.