Studies of an Enneanuclear Manganese Single-Molecule Magnet
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- 作者：Stergios Piligkos ; Gopalan Rajaraman ; Monica Soler ; Nadeschda Kirchner ; Joris van Slageren ; Roland Bircher ; Simon Parsons ; Hans-Ulrich Gü ; del ; Jens Kortus ; Wolfgang Wernsdorfer ; George Christou ; a
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：April 20, 2005
- 年：2005
- 卷：127
- 期：15
- 页码：5572 - 5580
- 全文大小：352K
- 年卷期：v.127,no.15(April 20, 2005)
- ISSN：1520-5126
文摘
The reaction of [Mn3O(O2CMe)6(py)3] with the tripodal ligand H3thme (1,1,1-tris(hydroxymethyl)ethane) affords the enneanuclear complex [Mn9O7(O2CCH3)11(thme)(py)3(H2O)2] 1·1MeCN·1Et2O. Themetallic skeleton of complex 1 comprises a series of 10 edge-sharing triangles that describes part of anidealized icosahedron. Variable temperature direct current (dc) magnetic susceptibility data collected inthe 1.8-300 K temperature range and in fields up to 5.5 T were fitted to give a spin ground state of S =17/2 with an axial zero-field splitting parameter D = -0.29 cm-1. Ac susceptibility studies indicate frequency-dependent out-of-phase signals below 4 K and an effective barrier for the relaxation of the magnetizationof Ueff = 27 K. Magnetic measurements of single crystals of 1 at low temperature show time- andtemperature-dependent hysteresis loops which contain steps at regular intervals of field. Inelastic neutronscattering (INS) studies on complex 1 confirm the S = 17/2 ground state and analysis of the INS transitionswithin the zero-field split ground state leads to determination of the axial anisotropy, D = -0.249 cm-1,and the crystal field parameter, B40 = 7(4) × 10-6 cm-1. Frequency domain magnetic resonancespectroscopy (FDMRS) determined the same parameters as D = -0.247 cm-1 and B40 = 4.6 × 10-6cm-1. DFT calculations are fully consistent with the experimental findings of two Mn(II) and four Mn(III)ions "spin up" and three Mn(IV) ions "spin down" resulting in the S = 17/2 spin ground state of the molecule,with D = -0.23 cm-1 and U = 26.2 K.