A Stable Hybrid Bisphosphonate Polyoxometalate Single-Molecule Magnet
A Stable Hybrid Bisphosphonate Polyoxometalate Single-Molecule Magnet
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DOI：
10.1002/chem.201200140
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发表时间：
2012-03-01
影响因子：
4.3
通讯作者：
Mialane, Pierre
中科院分区：
文献类型：
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作者：
El Moll, Hani;Dolbecq, Anne;Mialane, Pierre
聚氧乙烯酸盐（POM）化学的悠久历史最初以抗磁性物质的表征为特征。[1]然而，在过去的几十年里，已经看到了几个家庭的顺磁性POM分子的发展，显示出各种各样的结构和性能。这些实体可以是纳米级的，如通式{（Mo）Mo 5} 12 M30（M= Fe III，Cr III，VIV）的自旋受抑Keplerate簇的发现所例示的。[2]虽然尺寸小于这些钼化合物，但高核性多钒酸盐混合价物种也已被表征。在这些系统中观察到的出乎意料的强磁耦合已经在实验和理论上进行了详细的研究。[3]第三个也是最广泛的磁性POM家族是多钨酸盐。已经获得了大的簇合物，其中空的多钨酸盐配体包封3d [4]或4f [5]金属，并且这些系统中的大多数是纯无机的。特别是，迄今为止，在温和条件下合成的非常少的混合多核3d磁性多钨酸盐的特征在于。[6]此外，据我们所知，没有一般的方法制备杂化，可溶性，稳定的多钨酸盐封装的磁性集群已被提出。这与抗磁性多钨酸盐的情况形成鲜明对比，已报道了许多三醇官能化的有机硅烷基和有机锡衍生物。[7]基于混合镨的POM化学也已被广泛开发，但主要是封装最多一个3d阳离子的{Mo 6} Lindqvist和Anderson型系统已被用作连接各种有机基底的平台。[7]因此，建立一种方法，允许合理的合成稳定的混合多金属氧酸盐，包括几个二价或三价的3d金属中心，仍然是一个挑战。这种材料将在各种领域中引起兴趣，因为它们将允许将含有3d簇的POM共价接枝到一系列有机基底或表面上，从而制备新的功能材料。例如，光活性有机基团与多电致变色3d取代的无机实体的共价连接可以提供具有新性质的光学材料。或者，CoII取代的多钨酸盐已被证明是有效的光催化剂，[8]这本身可能会激发对相关杂化材料的研究。显然，混合三维磁性多钨酸盐在分子磁学领域也很有趣。自2008年以来，已知3d-[9]或4f-取代的[10]多钨酸盐可以表现为单分子磁体（SMM）。此外，POM SMM在单壁碳纳米管（SWCNT）上的沉积提供了证据，表明单个POM分子呈现出缓慢的磁化弛豫，[11]这是关于这种纳米复合材料作为信息存储设备的潜在用途的关键点。[12]然而，在这样的系统中，不可能控制SWCNT/POM界面。这是由于沉积的POM的纯无机性质-迄今报道的所有3D POM SMMs物种的特征。事实上，通过共价接枝或π-π堆叠以及POM/基底距离的控制来增强两种组分之间的相互作用显然意味着混合POM SMM系统的精细化。本文报道了聚阴离子[{（B-α-PW_9 O_（34）Co_3（OH）ACHTUNGTRENNUNG（H_2 O）_2ACHTUNGTRENNUNG（O_3 PC（O）ACHTUNGTRENNUNG（C_3 H_6 NH_3）-PO_3）}_2Co]_（14）（1）的结构表征。
The long history of polyoxometalate (POM) chemistry initially featured the characterization of diamagnetic species.[1] However, the last few decades have seen the development of several families of paramagnetic POM molecules that display a diverse range of structures and properties. These entities can be of nanosize scale, as exemplified by the discovery of the spin-frustrated Keplerate clusters of general formula {(Mo) Mo5} 12M30 (M= FeIII, CrIII, VIV).[2] Although of smaller size than these molybdenum compounds, high-nuclearity polyoxovanadate mixed-valent species have also been characterized. The unexpectedly strong magnetic couplings observed in a number of these systems have been studied in detail both experimentally and theoretically.[3] The third—and most extended—magnetic POM family is that of polyoxotungstates. Large clusters in which vacant polyoxotungstate ligands encapsulate 3d [4] or 4f [5] metals have been obtained, and most of these systems are purely inorganic. In particular, very few hybrid polynuclear 3d magnetic polyoxotungstates synthesized under mild conditions have been characterized to date.[6] Moreover, to the best of our knowledge, no general method for the preparation of hybrid, soluble, and stable polyoxotungstates encapsulating magnetic clusters has been proposed. This contrasts with the case of the diamagnetic polyoxotungstates, for which numerous triol-functionalized, organosilyl and organostannic derivatives have been reported.[7] Hybrid molybdenum-based POM chemistry has also been widely developed, but mainly {Mo6} Lindqvist and Anderson-type systems encapsulating a maximum of one 3d cation have been used as a platform for connecting various organic substrates.[7] The establishment of a method allowing the rational synthesis of stable hybrid POMs incorporating several divalent or trivalent 3d metal centers thus remains a challenge. Such materials would be of interest in various fields as they would permit the covalent grafting of POMs containing 3d clusters to a range of organic substrates or surfaces, and thus the elaboration of new functional materials. For example, the covalent connection of photoactive organic groups to multi-electrochromic 3d-substituted inorganic entities may afford optical materials with new properties. Alternatively, CoII-substituted polyoxotungstates have been shown to be efficient photocatalysts,[8] which may in itself motivate the search for related hybrid materials. Clearly, hybrid 3d magnetic polyoxotungstates are also interesting in the molecular magnetism field. Since 2008, it is known that 3d-[9] or 4f-substituted [10] polyoxotungstates can behave as single molecule magnets (SMMs). Moreover, deposition of POM SMMs on single-wall carbon nanotubes (SWCNTs) has provided evidence that individual POM molecules present a slow relaxation of the magnetization,[11] a crucial point with respect to the potential use of such nanocomposites as information storage devices.[12] However, in such a system, no control of the SWCNT/POM interface is possible. This is due to the purely inorganic nature of the deposited POM—a characteristic of all the 3d POM SMMs species reported to date. Indeed, the reinforcement of the interactions between the two components via covalent grafting or π–π stacking together with the control of the POM/substrate distance obviously implies the elaboration of hybrid POM SMM systems. Herein, we report the characterization of the polyanion [{(B-α-PW9O34) Co3 (OH) ACHTUNGTRENNUNG (H2O) 2ACHTUNGTRENNUNG (O3PC (O) ACHTUNGTRENNUNG (C3H6NH3)-PO3)} 2Co] 14À (1), which is built of a heptanuclear CoII core …