Coulombic Aggregations of MnIII salen-Type Complexes and Keggin-Type Polyoxometalates: Isolation of Mn2 Single-Molecule Magnets

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• 作者：Yuki Sawada ; Wataru Kosaka ; Yoshihito Hayashi ; Hitoshi Miyasaka
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：April 16, 2012
• 年：2012
• 卷：51
• 期：8
• 页码：4824-4832
• 全文大小：541K
• 年卷期：v.51,no.8(April 16, 2012)
• ISSN：1520-510X

文摘

The reaction of Mn^III salen-type complexes with di- and tetraanionic 伪-Keggin-type polyoxometalates (POMs) was performed, and three types of Coulombic aggregations containing Mn^III out-of-plane dimeric units (abbreviated as [Mn₂]²⁺) that are potentially single-molecule magnets (SMMs) with an S_T = 4 ground state were synthesized: [Mn₂(5-MeOsaltmen)₂(acetone)₂][SW₁₂O₄₀] (1), [Mn₂(salen)₂(H₂O)₂]₂[SiW₁₂O₄₀] (2), and [Mn(5-Brsaltmen)(H₂O)(acetone)]₂[{Mn₂(5-Brsaltmen)₂}(SiW₁₂O₄₀)] (3), where 5-Rsaltmen^{2鈥?/sup> = N,N鈥?(1,1,2,2-tetramethylethylene)bis(5-R-salicylideneiminate) with R = MeO (methoxy), Br (bromo) and salen2鈥?/sup> = N,N鈥?ethylenebis(salicylideneiminate). Compound 1 with a dianionic POM, [SW₁₂O₄₀]2鈥?/sup>, is composed of a 1:1 aggregating set of [Mn₂]2+/POM, and 2, with a tetraanionic POM, [SiW₁₂O₄₀]4鈥?/sup>, is a 2:1 set. Compound 3 with [SiW₁₂O₄₀]4鈥?/sup> forms a unique 1D coordinating chain with a [鈭抺Mn₂}鈥揚OM鈭抅2鈥?/sup> repeating unit, for which a hydrogen-bonded dimeric unit ([Mn(5-Brsaltmen)(H₂O)(acetone)]₂2+) is present as a countercation. Independent of the formula ratio of [Mn₂]2+/POM, MnIII dimers and POM units in 1鈥?b>3 form respective segregated columns along a direction of the unit cell, which make an alternate packing to separate evenly identical species in a crystal. The nearest intermolecular Mn路路路Mn distance is found in the order 2 < 3 < 1. The segregation of the [Mn₂]2+ dimer resulted in interdimer distances long enough to effectively reduce the intermolecular magnetic interaction, in particular in 1 and 3. Consequently, an intrinsic property, SMM behavior, of MnIII dimers has been characterized in this system, even though the interdimer interactions are still crucial in the case of 2, where a long-range magnetic order competitively affects slow relaxation of the magnetization at low ac frequencies.}