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 Mn-12 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 2.4CH(2)Cl(2) crystallizes in the triclinic space group P (1) over bar. The complex consists of a central [Mn-IV O-4(4)] cubane held within a nonplanar ring of eight Mn-III 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.