Synthesis, crystal structures, and magnetic properties of methoxido-bridged dinuclear Mn^III complexes derived from tri-dentate chelating ligands

Two new doubly methoxido-bridged Mn^III dinuclear complexes, [Mn^III(mphp)(μ-OCH₃)(CH₃OH)]₂·2CH₃OH (1) and ([Mn^III(ahbz)(μ-OCH₃)(CH₃OH)]₂·2CH₃OH (2), have been synthesized by using the tridentate ligands H₂mphp (H₂mphp = 2-methyl-6-(pyrimidin-2-yl-hydrazonomethyl)-phenol) and H₂ahbz (H₂ahbz = N-(2-amino-propyl)-2-hydroxy-benzamide). The complexes have been characterized by single-crystal X-ray diffraction analysis and magnetic measurements. Complexes 1 and 2 have a similar dimeric molecular structure. Two [Mn(L)(CH₃OH)]⁺ moieties (L²⁻ = mphp²⁻ or ahbz²⁻) are bridged by two μ-OCH₃⁻ groups in the axial-equatorial asymmetric manner. The coordination geometry of Mn^III is an axially elongated octahedron with two oxygens of a methanol ligand and a methoxido ligand situated at the axial positions. Magnetic measurements indicate that 1 and 2 exhibit antiferromagnetic behavior with the fitting parameter of J = −1.49(3) cm⁻¹, D = −1.3(1) cm⁻¹, g = 1.98(1) and zJ′ = −0.18(4) cm⁻¹ for 1, and J = −1.6(2) cm⁻¹, D = 4.5(3) cm⁻¹, g = 2.06(1) and zJ′ = 1.4(1) cm⁻¹ for 2 on the basis of the spin Hamiltonian Ĥ = −2JŜ_Mn1Ŝ_Mn2.