ic7007528_si_005.cif (56.65 kB)

High-Spin Mn Wheels

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posted on 20.08.2007, 00:00 by Maria Manoli, Alessandro Prescimone, Rashmi Bagai, Abhudaya Mishra, Muralee Murugesu, Simon Parsons, Wolfgang Wernsdorfer, George Christou, Euan K. Brechin
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 13 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.