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 P1. The cation consists of 10 MnIII ions, 8 (mu)3-O2- ions, 2 (mu)3-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 (mu)3-O atoms and six with (mu)2-O atoms. Complex 2·3CH2Cl2·H2O crystallizes in the triclinic space group P1. 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 (mu)3-OH- ions, three terminal chloride ions, and nine bridging and chelating hmp- ligands. Six hmp- ligands contain (mu)2-O atoms and three contain (mu)3-O atoms. The Cl- anion is hydrogen-bonded to the three (mu)3-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 (chi)MT value gradually decreases from 17.87 cm^3 mol^-1 K at 300 K to 1.14 cm^3 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 (DSz2), 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.