Synthesis and magnetic properties of μ-chloranilato-bridged binuclear iron(II) complexes

Five new mu-chloranilato-bridged binuclear iron(II) complexes of the formula [Fe-2(CA)L-4](ClO4)(2) [L denotes 4,4'-dimethyl-2,2'-bipyridine (Me-2-bpy); 5-chloro-1,10-phenanthroline (Cl-phen); 5-bromo-1,10-phenanthroline (Br-phen); 1,10-phenanthroline (phen) and 5-nitro-1,10-phenanthroline (NO2-phen)], where CA represents the dianion of chloranilic acid, have been synthesized and characterized. Based on elemental analyses, molar conductivity, magnetic moment of room-temperature measurements and spectroscopic studies, it is proposed that these complexes have CA-bridged structures and consist of two iron(II) ions, each in a distorted octahedral environment. The complexes [Fe-2(CA)(phen)(4)](ClO4)(2) (1) and [Fe-2(CA)(Me-2-bpy)(4)](ClO4)(2) (2) were further characterized by variable temperature magnetic susceptibility measurements (4 similar to 300 K) and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, (H) over cap = -2J (S) over cap(1) . (S) over cap(2), giving the exchange parameter J = -7.5 cm(-1) for (1) and J = -4.6 cm(-1) for (2). This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two Fe(II) ions within each molecule.