High-Spin Mn Wheels

The syntheses, structures, and magnetic properties of the complexes [MnIV4MnIII10MnII2O2(OCH3)12(tmp)8(O2CCH3)10]·3Et2O (1·3Et2O), [MnIV2MnIII18MnII2O6(OCH3)14(O2CCH3)16(tmp)8(HIm)2]·2CH3OH (2·2CH3OH), and [MnIV2MnIII18MnII2O6(OCH3)14(O2CCH3)16(Br−mp)8(HIm)2]·2C6H14·5CH3OH (3·2C6H14·5CH3OH) are reported. The unusual wheel-like
complexes were prepared by the treatment of [Mn3O(O2CCH3)6(HIm)3](O2CCH3) (HIm = imidazole) with 1,1,1-tris-(hydroxymethyl)propane (H3tmp) (1 and 2) or 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (Br−mpH3) (3) in
the presence of sodium methoxide (NaOCH3, 2, and 3) in CH3OH. Complex 1·3Et2O crystallizes in the triclinic
space group P1̄, while complexes 2·2CH3OH and 3·2C6H14·5CH3OH crystallize in the orthorhombic space
group Pbca. Direct current magnetic susceptibility data, collected for 1−3 in the respective 1.8−300 K and 0.1−7
T temperature and magnetic-field ranges, afford spin ground-state values of S = 14 ± 1 for complex 1 and S =
9 ± 1 for complexes 2 and 3. Alternating current susceptibility measurements performed on all three complexes in
the 1.8−10 K temperature range in a 3.5 G oscillating field at frequencies between 50 and 1000 Hz reveal out-of-phase χ‘ ‘M signals below approximately 3 K. Single-crystal hysteresis loop and relaxation measurements confirm
single-molecule magnetism behavior.