Synthesis, characterization and magnetism of heterodinuclear Cu(II)-Fe(II) complexes bridged by N,N′-oxamidobis(propionato)cuprate(II)

Six new copper(II)-iron(II) heterodinuclear complexes bridged by dianions of N,N'-oxamidobis(propionato)cuprate [Cu(obp)] and end-capped with 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen), 5-chioro-1,10-phenanthroline (Cl-phen), 5-bromo-1,10-phenanthroline (Br-phen) or 5-methyl-1,10-phenanthroline (Me-phen); namely [Cu(obp)FeL2] (L = bpy, phen, NO2-phen, Cl-phen, Br-phen, Me-phen), have been synthesized and characterized. Based on the elemental analyses, magnetic moments (at room temperature) and 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. The Cu(obp)Fe(bpy)(2) (1) and Cu(obp)Fe(phen)(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(Z1)(2), giving the exchange integrals J = -17.9 cm(-1) for (1) and J = -18.8 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.