Synthesis and magnetic analysis of μ-oxamido-bridged copper(II)-iron(II) heterodinuclear complexes

Five new copper(II)-iron(II) heterodinuclear complexes bridged by the dianion of N,N'-bis[3-(dimethylamino)propyl]oxamido (dmoxpn) and end-capped with 2,2'-bipyridine (bpy); 1,10-phenanthroline (phen); 5 -nitro- 1, 10-phenanthroline (NO2-phen); 5-chloro-1,10-phenanthroline (Cl-phen) or 5-bromo-1,10-phenanthroline (Br-phen); namely [Cu(dmoxpn)FeL2](ClO4)(2) (L = bpy, phen, NO2-phen, Cl-phen, Br-phen), have been synthesized and characterized. Based on elemental analyses, magnetic moments (at room temperature), molar conductivity measurements, and spectroscopic studies, extended oxamido-bridged structures consisting of a copper(II) ion and an iron(II) ion, which have a square-planar environment and an octahedral environment, respectively, are proposed for these complexes. The [Cu(dmoxpn)Fe(bpy)(2)](ClO4)(2) (1) and [Cu(dmoxpn)Fe(phen)(2)](ClO4)(2) (2) complexes have been further characterized by variable temperature magnetic susceptibility (4.2 similar to 300 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)(Z), giving the exchange integrals J = -15.9 cm(-1) for (1) and J = -17.5 cm(-1) for (2). These results indicated that the spin coupling between the adjacent copper(II) and iron(II) ions through oxamido-bridge in both complexes (1) and (2) is antiferromagnetic. The influence of methyl (-CH3) substituents in the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.