Synthesis and Magnetic Properties of mi-Oxalato-Bridged Cu(II)-Fe(III)-Cu(II) Heterotrinuclear Complexes

Three new _-oxalato-bridged copper(II)-iron(III)-copper(II) heterotrinuclear complexes described by the overall formula [Cu2Fe(ox)3L2]ClO4, where ox represents the oxalato dianions and L stands for 5-phenyl-1,10-phenanthroline (Ph-phen), 4,7-diphenyl- 1,10-phenanthroline (Ph2-phen) or 5-chloro-1,10-phenanthroline (Cl-phen), have been synthesized and characterized by elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR and electronic spectral studies. It is proposed that these complexes have extended ox-bridged structures, consisting of two copper(II) and an iron(III) ions, in which the central iron(III) ion has an octahedral environment and the end capped two copper(II) ions have a square-planar environment. The variable-temperature susceptibilities of [Cu2Fe(ox)3(Ph-phen)2]ClO4 complex were measured and studied in the 4.2~300 K range. The least-squares fit of the experimental susceptibility based on the spin Hamiltonian operator, _ _ _ H = JS S 1 2 _ _ 2 , yielded J = -9.89 cm-1. The magnetic coupling parameter is consistent with an antiferromagnetic exchange interaction between the copper(II) and iron(III) ions through the oxalato-bridge in the complex.