Pressure-Tuning Interactions in Molecule-Based Magnets

在优化功能材料的性能时，详细了解结构如何影响性能是至关重要的。确定最重要的结构参数是耗时的，通常需要对材料进行多种不同的化学修饰，确定其晶体结构，测量其物理性质，然后寻找结构-性质的相关性。还必须假定化学修饰除了使结构扭曲外没有其他影响，但通常情况并非如此。高压提供了一种绕过这些困难的方法。压力可以用来扭曲材料，而不需要化学改性。可以在高压下进行晶体结构和物理性能测量，从而可以研究同一材料在不同变形状态下的性能，为研究结构与性能之间的相关性提供了最直接的方法。在本提案中，我们将重点关注连接到延伸链，网络或框架中的分子基磁铁的结构-性质关系，使用高压晶体学，磁测量，光谱学和模拟的组合，这将利用英国在极端条件研究方面的独特能力。扩展材料是非常有趣的，因为一个地方的小变形会通过磁中心之间的强化学联系传播到整个材料，使磁性能对结构变化非常敏感。我们将设计和建造新的仪器用于在高压和低温下的磁化率和衍射测量，我们将利用这些新的仪器和方法来研究两类重要的磁性材料。一维磁性材料是发现和理解奇异物理现象的沃土。单链磁体（scm）的磁性行为从根本上受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伊辛类各向异性的影响，所有这些都对压力敏感。我们已经证明，这些参数可以在单分子磁体（SMMs）中进行压力调节，对于scm也是如此。在3-D框架中，磁性可以与孔隙度相结合，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了类似钻石的框架。在这两种情况下，客体分子都会影响磁有序温度。一些金属有机骨架表现出自旋交叉行为，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框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，宿主和客体之间的相互作用，以及纳入孔隙的客体分子的数量，从而在宿主-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.