A calix[4]arene 3d/4f magnetic cooler.
A calix[4]arene 3d/4f magnetic cooler.
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DOI：
10.1002/anie.200905012
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发表时间：
2009-12
影响因子：
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通讯作者：
G. Karotsis;M. Evangelisti;S. Dalgarno;E. Brechin
中科院分区：
文献类型：
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作者：
G. Karotsis;M. Evangelisti;S. Dalgarno;E. Brechin
配位化学家成功地制造出具有迷人物理性质的分子（通常是美观的），这源于对配体设计、金属同一性和加热制度对簇对称、拓扑和核性的影响的系统探索。分子纳米磁体的设计——用来研究基于自旋的固态量子比特和分子自旋电子学可能实现的模型系统——近年来一直是人们非常感兴趣的主题，因为它们的分子性质和固有的物理特性允许在经典物理学和量子物理学之间进行交叉观察。因此，新型分子纳米磁体的合成仍然是一个令人兴奋的挑战，但迄今为止所使用的有机配体的范围却令人惊讶地有限。毫无疑问，最成功的途径是在自组装中使用小而灵活的多齿配体。另一种方法是将磁性骨架完全封装在一个大的刚性有机或无机护套中，其双重作用还可以包括引入氧化还原活性、表面相容性或简单地去除/控制偶极相互作用。杯状芳烃（C4s）是典型的碗状分子，已被用于形成各种纳米尺度的超分子结构。它们的刚性构象可用于自组装，或与上边缘的功能化相结合，为组装指导金属中心提供结合位点。[10]因此，这些分子的多酚性质使它们成为分离顺磁性团簇化合物的良好配体候选者。在这方面，只有一种具有超过四种过渡金属的簇化合物已被证明与亚甲基桥接对叔丁基杯[4]芳烃1形成（图1a）。Thiacalix[4]芳烃及其氧化衍生物2-4（图1b）具有额外的供体原子，这些原子已被用于形成许多多核过渡金属或Ln簇。分子骨架周围额外的供体原子（相对于1）通过参与金属簇框架内的键合，在支持复合物形成中起关键作用。就我们的目的而言，易于接近的亚甲基桥接c4具有1)在碗形大环的下边缘形成新的簇化合物的潜力，2)容易改变上边缘的性质，从而进入包含超分子构建块的巨大新金属簇库。因此，这些特征可能允许控制簇之间的相互作用（从而调节它们在固态中的取向），或者通过改变杯状[4]芳烃的上边缘来改变簇隔离（或封装）的程度。我们最近报道了第一个锰簇的形成和第一个用亚甲基桥接C4分离的单分子磁铁（SMM）（图1c）。混合价mn2mnii复合物位于两个图1之间。a)对叔丁基杯[4]芳烃用于过渡金属簇的形成。b)在过渡和镧系金属团簇形成中使用的thacalix[4]芳烃。c)与1形成的mn2mn2smm。[14]为清楚起见，省略氢原子。
The success with which coordination chemists have produced (often aesthetically pleasing) molecules with fascinating physical properties is derived from the systematic exploration of the effects of ligand design, metal identity, and heating regime upon cluster symmetry, topology, and nuclearity. The design of molecular nanomagnets—model systems with which to investigate the possible implementation of spinbased solid-state qubits and molecular spintronics—has been the subject of much interest in recent years because their molecular nature and inherent physical properties allow the crossover between classical and quantum physics to be observed. The synthesis of new types of molecular nanomagnets therefore remains an exciting challenge, but the range of organic ligands employed thus far is surprisingly restricted. Undoubtedly the most successful route has been to employ small, flexible polydentate ligands in self-assembly. An alternative approach would be to entirely encapsulate the magnetic skeleton within a large rigid organic or inorganic sheath whose dual role could also include the introduction of redox activity, surface compatibility, or simply the removal/control of dipolar interactions. Calix[4]arenes (C4s) are typically bowl-shaped molecules which have been exploited in the formation of various nanometer-scale supramolecular architectures. Their rigid conformations can be utilized in self-assembly, or combined with functionalization at the upper rim to present binding sites for assembly-directing metal centers. 10] The polyphenolic nature of these molecules therefore renders them good ligand candidates for the isolation of paramagnetic cluster compounds. In this regard only one cluster compound, having greater than four transition metals, has been shown to form with methylene-bridged para-tert-butylcalix[4]arene 1 (Figure 1a). Thiacalix[4]arenes and their oxidized derivatives 2–4 (Figure 1b) possess additional donor atoms, and these have been used in the formation of a number of polynuclear transition-metal or Ln clusters. The additional donor atoms (relative to 1) around the molecular skeleton play a key role in supporting complex formation by taking part in the bonding within the metal-cluster framework. For our purposes, readily accessible methylene-bridged C4s present the potential to 1) form novel cluster compounds at the lower rim of the bowl-shaped macrocycles, and 2) easily alter the upper-rim properties to access a vast library of new metal clusters containing supramolecular building blocks. These features may therefore allow control of the interactions between clusters (thereby modulating their orientation in the solid state), or variation of the degree of cluster isolation (or encapsulation) through alteration of the upper rim of the calix[4]arene. We have recently reported the formation of the first Mn cluster and the first single-molecule magnet (SMM) to be isolated using any methylene-bridged C4 (Figure 1c). The mixed-valent Mn2Mn II 2 complex is housed between two Figure 1. a) para-tert-Butylcalix[4]arene sused in transition-metal cluster formation. b) Thiacalix[4]arenes used in transitionand lanthanidemetal cluster formation. c) Mn2Mn II 2 SMM formed with 1. [14] Hydrogen atoms omitted for clarity.