Pressure-Tuning Interactions in Molecule-Based Magnets

在优化功能材料的性能时，必须详细了解结构如何影响性能。确定最重要的结构参数是耗时的，通常通过制备材料的许多不同化学改性，确定其晶体结构，测量其物理性质，然后寻找结构-性质相关性来研究。还必须假设化学修饰除了扭曲结构之外没有影响，而情况往往并非如此。高压提供了一种解决这些困难的方法。压力可以用来使材料变形，而不需要化学改性。晶体结构和物理性能测量都可以在高压下进行，因此可以在不同的变形状态下研究同一材料的性能，为研究结构和性能之间的相关性提供了最直接的方法。在这项提案中，我们专注于使用高压晶体学，磁性测量，光谱学和模拟相结合的分子磁体连接到扩展链，网络或框架中的结构-性能关系，这将利用英国在极端条件下的独特能力研究。延伸材料是非常感兴趣的，因为在一个网站上的一个小的扭曲是通过磁中心之间的强化学联系传播到整个材料，使磁性能非常敏感的结构变化。我们将设计和建造在高压和低温下进行磁化率和衍射测量的新仪器，我们将利用这些新仪器和方法来研究两类重要的磁性材料。1-D磁性材料代表了发现和理解奇异物理现象的肥沃操场。单链磁体（SCM）的磁性行为基本上取决于最近邻交换相互作用（链内交换）的大小，链间相互作用的程度和Ising类各向异性-所有这些都对压力敏感。我们已经表明，这些参数可以在单分子磁体（SMM）中进行压力调节，对于SCM也应该如此。在3-D框架中，磁性可以与孔隙率相结合，因此包含不同的客体分子提供了另一种控制磁性的方法。普鲁士蓝类似物由氰化物阴离子连接的不同金属阳离子组成，而金属羧酸盐则构建类金刚石框架。在这两种情况下，客体分子影响磁有序温度。一些金属有机框架显示自旋交叉行为，其中金属离子的不同电子构型在不同条件下是稳定的。从一种形式到另一种形式的转变受到占据骨架孔隙的客体分子的影响。高压将使我们能够控制框架本身的结构，主体和客体之间的相互作用，以及掺入孔中的客体分子的数量，从而在主体-客体相互作用和磁性之间提供定量联系。

In optimizing the properties of functional materials it is essential to understand in detail how structure influences properties. Identification of the most important structural parameters is time-consuming and usually investigated by preparing many different chemical modifications of a material, determining their crystal structures, measuring their physical properties and then looking for structure-property correlations. It is also necessary to assume that the chemical modifications have no influence other than to distort the structure, which is often not the case. High pressure offers a way around these difficulties. Pressure can be used to distort a material without the need for chemical modification. Both crystal structures and physical property measurements can be conducted at high pressure, so that the properties of the same material can be studied in different states of distortion, providing the most direct way to study correlations between structure and properties. In this proposal we focus on structure-property relationships in molecule-based magnets connected into extended chains, networks or frameworks using a combination of high pressure crystallography, magnetic measurements, spectroscopy and simulation which will exploit the UK's unique capabilities in extreme conditions research. Extended materials are of great interest because a small distortion at one site is propagated throughout the material by the strong chemical links between the magnetic centres, making the magnetic properties very sensitive to structural changes. We will design and build new instruments for magnetic susceptibility and diffraction measurements at high pressure and low temperature and we will exploit these new instruments and methodology to study two important classes of magnetic material. 1-D magnetic materials represent a fertile playground for discovering and understanding exotic physical phenomena. The magnetic behaviour of Single-Chain Magnets (SCMs) is fundamentally governed by the magnitude of nearest neighbour exchange interactions (intra-chain exchange), the extent of inter-chain interactions, and Ising-like anisotropy - all of which are sensitive to pressure. We have already shown that these parameters can be pressure-tuned in Single-Molecule Magnets (SMMs) and the same should be true for SCMs In 3-D frameworks magnetism can be combined with porosity, so that inclusion of different guest molecules provides another means for controlling magnetic properties. Prussian Blue Analogues consist of different metal cations linked by cyanide anions, while metal carboxylates build diamond-like frameworks. In both cases guest molecules influence magnetic ordering temperatures. Some metal-organic frameworks show spin-crossover behaviour, where different electronic configurations of the metal ions are stable under different conditions. The transition from one form to another is influenced by guest molecules which occupy the pores of the framework. High pressure will enable us to control the structure of the framework itself, the interactions between the host and the guest, and the number of guest molecules incorporated into the pores, providing a quantitative link between host-guest interactions and magnetism.