Syntheses and Magnetism of μ-4-Nitrophthalato Manganese(II) Binuclear Complexes

Abstract

Three new manganese(II) binuclear complexes, namely [Mn₂(NPTA)(Phen)₄](ClO₄)₂.2H₂O (complex 1), [Mn₂(NPTA)(Nphen)₄]-(ClO₄)₂.4H₂O(complex 2) and [Mn₂(NPTA)(Bpy)₄](ClO₄)₂ (complex 3) (NPTA = 4-nitrophthalate, Phen = 1,10-phenanthroline, Nphen = 5-nitro-1,10-phenanthroline, Bpy = 2,2′-bipyridyl), have been synthesized with 4-nitrophthalato as bridging ligand. The complexes were characterized by elemental analyses, IR, molar conductance, electronic reflection spectra and ESR spectra. These complexes are proposed to have extended 4-nitrophthalato-bridged structures and to consist of two manganese(II) atoms in a distorted octahedral environment. The temperature dependent magnetic susceptibility of complex 1 was measured over the temperature range 4.2–300 K. The magnetic coupling parameter is consistent with antiferromagnetic exchange between the two manganese(II) centers and fits the data of a binuclear magnetic exchange model based on the Hamiltonian operator (H =-2JS₁S₂), giving the antiferromagnetic coupling parameter of 2J = −0.7 cm⁻¹. This means that there is a very weak antiferromagnetic spin-exchange interaction between the bridged manganese(II) ions.