Synthesis, characterization and magnetic analysis of bromanilato-bridged binuclear iron(III) complexes

Five new bromanilato-bridged binuclear iron(III) complexes have been synthe sized and characterized, namely [Fe-2(BA)L-4](ClO4)(4), where HA represents the dianion of bromanilic acid and L denotes 2,2'-bipyridine (bpy); I,10-p henanthroline (phen), 5-chloro-1,10-phenanthroline (Cl-phen); 5-bromo-1,10- phenanthroline (Br-phen) or 5-nitro-1,10-phenanthroline (NO2-phen). Based o n elemental analyses, molar conductivity, magnetic moment of room-temperatu re measurements, IR and electronic spectra studies, these complexes are pro posed to have extended HA-bridged structures consisting of two iron(III) io ns, each in a distorted octahedral environment. The complexes [Fe-2(BA)(bpy )(4)](ClO4)(4) (1) and [Fe-2(BA)(phen)(4)](ClO4)(4) (2) were further charac terized by variable temperature (4.2 similar to 300 K) magnetic susceptibil ity measurements and the observed data were successfully simulated by the e quation based on the spin Hamiltonian operator, (H) over cap = -2J (S) over cap(1) . (S) over cap(2), giving the exchange parameter J = -3.6 cm(-1) fo r(1) and J = -7.9 cm(-1) for (2). These results are commensurate with weak antiferromagnetic spin-exchange interaction between the two Fe(III) ions wi thin each molecule. The influence of halogen substituents in the bridging l igand on magnetic interactions between the metal ions of this kind of compl exes is also discussed.