Heptanuclear and Decanuclear Manganese Complexes with the Anion of 2-Hydroxymethylpyridine

The synthesis and magnetic properties are reported of two new clusters [Mn10O4(OH)2(O2CMe)8(hmp)8](ClO4)4 (1)
and [Mn7(OH)3(hmp)9Cl3](Cl)(ClO4) (2). Complex 1 was prepared by treatment of [Mn3O(O2CMe)6(py)3](ClO4) with
2-(hydroxymethyl)pyridine (hmpH) in CH2Cl2, whereas 2 was obtained from the reaction of MnCl2·4H2O, hmpH,
and NBun4MnO4 in MeCN followed by recrystallization in the presence of NBun4ClO4. Complex 1·2py·10CH2Cl2·2H2O crystallizes in the triclinic space group P1̄. The cation consists of 10 MnIII ions, 8 μ3-O2- ions, 2 μ3-OH-
ions, 8 bridging acetates, and 8 bridging and chelating hmp- ligands. The hmp- ligands bridge through their O
atoms in two ways:  two with μ3-O atoms and six with μ2-O atoms. Complex 2·3CH2Cl2·H2O crystallizes in the
triclinic space group P1̄. The cation consists of four MnII and three MnIII ions, arranged as a Mn6 hexagon of
alternating MnII and MnIII ions surrounding a central MnII ion. The remaining ligation is by three μ3-OH- ions, three
terminal chloride ions, and nine bridging and chelating hmp- ligands. Six hmp- ligands contain μ2-O atoms and
three contain μ3-O atoms. The Cl- anion is hydrogen-bonded to the three μ3-OH- ions. Variable-temperature
direct current (dc) magnetic susceptibility data were collected for complex 1 in the 5.00−300 K range in a 5 kG
applied field. The χMT value gradually decreases from 17.87 cm3 mol-1 K at 300 K to 1.14 cm3 mol-1 K at 5.00
K, indicating an S = 0 ground state. The ground-state spin of complex 2 was established by magnetization
measurements in the 0.5−3.0 T and 1.80−4.00 K ranges. Fitting of the data by matrix diagonalization, incorporating
only axial anisotropy (DŜz2), gave equally good fits with S = 10, g = 2.13, D = −0.14 cm-1 and S = 11, g =
1.94, D = −0.11 cm-1. Magnetization versus dc field scans down to 0.04 K reveal no hysteresis attributable to
single-molecule magnetism behavior, only weak intermolecular interactions.