Two-step spin conversion in a cyanide-bridged ferrous square.
Two-step spin conversion in a cyanide-bridged ferrous square.
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DOI：
10.1002/anie.200502216
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发表时间：
2005-10
影响因子：
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通讯作者：
M. Nihei;M. Ui;Masanobu Yokota;Lingqin Han;A. Maeda;H. Kishida;H. Okamoto;H. Oshio
中科院分区：
文献类型：
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作者：
M. Nihei;M. Ui;Masanobu Yokota;Lingqin Han;A. Maeda;H. Kishida;H. Okamoto;H. Oshio
开发先进分子器件开关的一条重要途径涉及分子水平上磁特性的变化。 [1]过渡金属配合物中的自旋交叉是由于热、压力或光照射而发生自旋态转换，是设计分子开关的关键现象。 [2]由于氰化物桥配合物相对容易合成并且具有丰富的磁性，因此成为该领域研究的重点。普鲁士蓝是一种居里温度 (TC) 为 5.6 K 的铁磁体，[3] 和一些异质金属类似物是有序温度高达 372K 的高 TC 磁体，是众所周知的氰化物桥接金属配合物的示例。 [4]氰基金属盐中的金属离子通常采用低自旋构型。然而，引入具有弱配体场强度的配体和异金属离子的组合提供了有趣的磁特性，例如自旋交叉、[5]光感磁、[6]和超顺磁性。[7]此外，具有多个自旋交叉位点的分子可用作多级分子开关。最近，报道了一些热诱导的两步自旋交叉配合物。[8]然而，此类系统的数量仍然很少。[9]我们研究了氰化物桥联分子方体[Fe2M2 (μ-CN) 4 (bpy) 8] n+(M=后第一行过渡金属离子；bpy= 2, 2'-联吡啶)，其中氰化物离子桥接四个金属离子形成大环四核核。 [10]我们发现用三(2-吡啶甲基)胺(tpa)代替bpy后，FeII中心的配体场强减弱，生成的亚铁方形[FeII 4 (μ-CN) 4 (bpy) 4 (tpa) 2]-(PF6) 4 (1-(PF6) 4)表现出两步自旋转换。 [Fe (CN) 2 (bpy) 2]· 3 的反应H2O [11] 与 FeCl2·4 H2O、tpa,[12] 和 NH4PF6 在甲醇中反应得到四核配合物 1 (PF6) 4.[13]在100、200和300 K下进行X射线晶体结构分析，200 K下14+的分子结构如图1所示。
An important route to the development of switches for advanced molecular devices involves changes in magnetic properties at the molecular level.[1] Spin crossover in transition-metal complexes, in which spin-state conversions occur as a result of heat, pressure, or light irradiation, is a key phenomenon for designing molecular switches.[2] Because cyanide-bridged complexes are relatively easy to synthesize and have rich magnetic properties, they have become the focus of this area of research. Prussian blue, which is a ferromagnet with a Curie temperature (TC) of 5.6 K,[3] and some heterometal analogues that are high-TC magnets with an ordering temperature up to 372K are examples of wellknown cyanide-bridged metal complexes.[4] Metal ions in cyanometalates typically adopt a low-spin configuration. However, introduction of ligands with weak ligand-field strengths and combinations of heterometal ions afford interesting magnetic properties such as spin crossover,[5] photoinduced magnetism,[6] and superparamagnetism.[7] Furthermore, molecules with more than one spin-crossover site can be used as multistepped molecular switches. Recently, some thermally induced, two-step spin-crossover complexes were reported.[8] However, the number of such systems is still small.[9] We have studied cyanide-bridged molecular squares,[Fe2M2 (μ-CN) 4 (bpy) 8] n+(M= late first-row transition-metal ion; bpy= 2, 2’-bipyridine), in which cyanide ions bridge four metal ions to form the macrocyclic tetranuclear core.[10] We found that by replacing bpy with tris (2-pyridylmethyl) amine (tpa), the ligand-field strength on the FeII centers is weakened and the resulting ferrous square,[FeII 4 (μ-CN) 4 (bpy) 4 (tpa) 2]-(PF6) 4 (1-(PF6) 4), showed two-step spin conversion.The reaction of [Fe (CN) 2 (bpy) 2]· 3 H2O [11] with FeCl2· 4 H2O, tpa,[12] and NH4PF6 in methanol afforded the tetranuclear complex 1 (PF6) 4.[13] X-ray crystal structure analyses were performed at 100, 200, and 300 K, and the molecular structure of 14+ at 200 K is shown in Figure 1.