Synthesis and magnetic interaction of μ-2-chloroterephthalato binuclear iron(II) complexes

Four mu-2-chloroterephthalato binuclear iron(II) complexes, namely [Fe-2(CTPHA)L-4](ClO4)(2), where L stands for 4,4'-dimethyl-2,2'-bipyridine (Me-2-bpy); 2,9-dimethyl-1, 10-phenanthroline (Me-2-phen); 5-chloro-1, 10-phenanthroline (Cl-phen); 4, 7-diphenyl-1, 10-phenanthroline (Ph-2-phen), respectively, and CTPHA represents 2-chloroterephthalate dianion, have been synthesized and characterized. Based on the elemental analyses, molar conductance measurements and spectroscopic stud ies, extended CTPHA-bridged structures consisting of two iron(II) ions, each in a distorted octahedral environment, are proposed for these complexes. [Fe-2(CTPHA)-(Me-2-bpy)(4)] (ClO4)(2) (1) and [Fe-2(CTPHA).(Me-2-phen)(4)]( ClO4)(2) (2) complexes were characterized by variable temperature magnetic susceptibility (4-300 K) measurements 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 integrals J = - 1.28 cm(-1) for 1 and J = -1.85 cm(-1) for 2. These results indicate the presence of a weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule.