Quantum Tunneling of Magnetization in a New [Mn18]2+ Single-Molecule Magnet with S = 13
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- 作者：Euan K. Brechin ; Colette Boskovic ; Wolfgang Wernsdorfer ; Jae Yoo ; Akira Yamaguchi ; E. Carolina Sañ ; udo ; Thomas R. Concolino ; Arnold L. Rheingold ; Hidehiko Ishimoto ; David N. Hendrickson ; and Geo
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：August 21, 2002
- 年：2002
- 卷：124
- 期：33
- 页码：9710 - 9711
- 全文大小：129K
- 年卷期：v.124,no.33(August 21, 2002)
- ISSN：1520-5126
文摘
The reaction between 2-(hydroxyethyl)pyridine (hepH) and a 2:1 molar mixture of [Mn3O(O2CMe)6(py)3](ClO4) and [Mn3O(O2CMe)6(py)3](py) in MeCN leads to isolation of [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 (1) in 10% yield. The complex is 2MnII,16MnIII and consists of a Mn4O6 central unit to either side of which is attached a Mn7O9 unit. Magnetization data collected in the 2.0-4.0 K and 20-50 kG ranges were fit to yield S = 13, g = 1.86, and D = -0.13 cm-1 = -0.19 K, where D is the axial zero-field splitting parameter. AC susceptibility studies in the 0.04-4.0 K range at frequencies up to 996 Hz display out-of-phase (
es/gifchars/chi.gif" BORDER=0 >M' ') signals, indicative of a single-molecule magnet (SMM). Magnetization vs applied DC field scans exhibit hysteresis at <1.0 K, confirming 1 to be a SMM. DC magnetization decay data were collected on both a microcrystalline sample and a single crystal, and the combined data were used to construct an Arrhenius plot. Between 3.50 and 0.50 K, the relaxation rate is temperature-dependent with an effective barrier to relaxation (Ueff) of 14.8 cm-1 = 21.3 K. Below ca. 0.25 K, the relaxation rate is temperature-independent at 1.3 × 10-8 s-1, indicative of quantum tunneling of magnetization (QTM) between the lowest energy Ms = ±13 levels of the S = 13 state. Complex 1 is both the largest spin and highest nuclearity SMM to exhibit QTM.