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

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 P1. The complex consists of a central [MnIV4O4] cubane held within a nonplanar ring of eight MnIII ions by eight (mu)3-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.