Single-molecule magnets. A Mn12 complex with mixed carboxylate-sulfonate ligation: [Mn12O12(O2CMe)8(O3SPh)8(H2O)4]

Abstract

The synthesis and magnetic properties of a new member of the Mn₁₂ single-molecule magnet family, [Mn₁₂O₁₂(O₂CMe)₈(O₃SPh)₈(H₂O)₄] (2), are reported. The compound was prepared by treatment of [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄] (1) with eight equivalents of PhSO₃H in MeCN. Complex 2·4CH₂Cl₂ crystallizes in the triclinic space group P. The complex consists of a central [Mn^IV₄O₄] cubane held within a nonplanar ring of eight Mn^III ions by eight μ₃-O²⁻ ions. Eight bridging acetate groups occupying equatorial sites, eight bridging benzenesulfonate groups in axial sites, and four terminal water molecules complete the peripheral ligation of the molecule. The spin of the ground state was established by magnetization measurements in the 2.00–7.00 T field range and 1.80–4.00 K temperature range. Fitting of the reduced magnetization data by full matrix diagonalization, incorporating only axial anisotropy, gave S = 10, g = 1.96 and D = −0.34 cm⁻¹. The cluster exhibits out-of-phase ac susceptibility signals and temperature-dependent hysteresis loops at temperatures below 4.00 K, establishing 2 as a new single-molecule magnet.