New Structural Types of Mn16 Single-Molecule Magnets: W-Shaped Topology from Reductive Aggregation

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• 作者：Annaliese E. Thuijs ; Philippa King ; Khalil A. Abboud ; George Christou
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：September 21, 2015
• 年：2015
• 卷：54
• 期：18
• 页码：9127-9137
• 全文大小：713K
• ISSN：1520-510X

文摘

Two new Mn₁₆ clusters are reported: [Mn₁₆O₁₀(OH)₃(OMe)₈(O₂CPhBu^t)₁₇(MeOH)₅] (2) and [Mn₁₆O₁₆(OMe)₆(O₂CPh)₁₂(NO₃)₄(MeOH)₂(H₂O)₄] (3). The complexes were obtained by reductive aggregation of MnO₄^{鈥?/sup> in CH₂Cl₂/MeOH, and oxidation of MnII and preformed (NnBu₄)[Mn₄IIIO₂(O₂CPh)₉(H₂O)] with CeIV, respectively. The core of 2 has a Mn₁₆III core with an unusual 1:2:3:4:3:2:1 layer structure and a W-shaped pleated topology, whereas 3 contains a central 2 脳 3 Mn₆IV planar grid held within a nonplanar Mn₁₀III loop and is a rare example of a complex with nitrate ions bridging like carboxylate ions. Variable-temperature, solid-state dc susceptibility, and ac susceptibility studies reveal that 2 and 3 possess S = 12 and S = 8 ground states, respectively. Fits of dc magnetization data collected over a temperature range of 1.8鈥?.0 K and a magnetization range of 0.1鈥? T were fit to give S = 12, D = 鈭?.16(2) cm鈥?, g = 1.98(3) for 2 and S = 8, D = 鈭?.22(1) cm鈥?, g = 1.99(2) for 3, where D is the axial zero-field splitting parameter. The ac in-phase (蠂_M鈥?/sup>T) susceptibility below 15 K confirmed the ground-state spin values of 2 and 3, as determined from dc data, and the appearance of frequency-dependent out-of-phase (蠂_M鈥?/sup>) signals revealed that both complexes are new single-molecule magnets (SMMs). Fits of the ac data gave U_eff = 49.7(1) K and 蟿₀ = 4.32 脳 10鈥? s for 2 and U_eff 鈮?14.0 卤 2 cm鈥? and 蟿₀ 鈮?3.2 卤 0.5 脳 10鈥? s for 3, where U_eff is the effective barrier to magnetization relaxation and 蟿₀ is the pre-exponential factor. Thus, complexes 2 and 3 are two new members of a growing family of Mn₁₆ clusters, and two new examples of high-nuclearity SMMs, with the U_eff for 2 approaching the value for the prototypical SMM family, [Mn₁₂O₁₂(O₂CR)₁₆(H₂O)₄].}