Synthesis and Magnetic Studies of Binuclear Iron(II) Complexes Bridged by μ-2-Chloroterephthalato Groups

Abstract

Four new 2-μ-chloroterephthalato binuclear iron(II) complexes of the formula [Fe2(CTPHA)L4]SO4, where CTPHA denotes the 2-chloro-terephthalate dianion and L represents 2, 2′-bipyridine (bpy); 1, 10-phenanthroline (phen); 5-methyl-1, 10-phenanthroline (Me-phen); 5-nitro-l, 10-phenanthroline (NO2-phen), respectively, have been synthesized and characterized by elemental analyses, molar conductance and room-temperature magnetic moments measurements, and IR and electronic spectral studies. It is proposed that these complexes have extended CTPHA-bridged structures and consist of two iron(II) ions, each in an octahedral environment. The variable-temperature magnetic susceptibilities (4–300 K) of the [Fe2(CTPHA)(bpy)4]SO4 (1) and [Fe2(CTPHAXphen)4]SO4 (2) complexes have been studied. A satisfactory fit to the theoretical curve derived from the spin Hamiltonian operator, Ĥ = -2Jş, ş2 was obtained by the least squares method. The exchange integral, J, was found to be -2. 25 cm−1 for (1) and -1. 32 cm−1 for (2), indicating that weak antiferromagnetic spin-exchange interaction is present in the binuclear iron(II) complexes. The influence of the bridge ligand chlorine substituent upon the magnetic interaction between the metals of this kind of complexes is also discussed.