Synthesis, Characterization and Magnetic Analysis of Bromanilato-Bridged Binuclear Iron(II) Complexes

Five new bromanilato-bridged binuclear iron(III) complexes have been synthesized and characterized, namely [fe(BA)L4](ClO4)4 where BA represents the dianion of bromanilic acid and L denotes 2,2'-bipyrydine (bpy); 1;10-phenanthroline (phen), 5-chloro-1,10-phenanthroline (Cl-phen), 5-bromo-1,10-phenanthroline (Br-phen) or 5-nitro-1,10-phenanthroline (NO2-phen). Based on elemental analyses, molar conductivity, magnetic moment of room-temperature measurements, IR and electronic spectra studies, these complexes are proposed to have extended BA-bridged structures consisting of two iron(III) ions, each in a distorted octahedral environment. The complexes [Fe2(BA)(bpy)4](ClO4)4 (1) and [Fe2(BA)(phen)4](ClO4)4 (2) were further characterized by variable temperature (4.2-300 K) magnetic susceptibility measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H=-2jS1*S2, giving the exchange parameter J=-3.6 cm-1 for (1) and J=-7.9 cm-1 for (2). These results are comensurate with weak antiferromagnetic spin-exchange interaction between the two Fe(III) ions within each molecule. The influence of halogen substituents in the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.