Low-Coordinate and Radical-Bridged Lanthanide Molecular Nanomagnets

低配位和自由基桥接镧系元素分子纳米磁体

• 批准号: 1782266
• 金额: --
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1782266
• 关键词: Low; Coordinate; Radical; Bridged; Lanthanide

The synthesis of complex magnetic materials from simple chemical building blocks encapsulates the intrinsic fascination of molecular magnetism. Molecular magnets are typically designed using bottom-up approaches that provide access to experimental testbeds for theoretical models such as ligand field theory. The molecular approach also enables rational approaches to applications, such as the use of transition metal complexes as qubits for quantum computing, the use of lanthanide complexes as magnetic refrigerants, and in NMR spectroscopy as shift reagents and in magnetic resonance imaging.Considerable effort is currently focused on the phenomenon of magnetic bistability in molecular systems, whereby two different magnetic responses can be measured under identical physical conditions. Two important types of bistable molecular magnets are spin-crossover (SCO) compounds and single-molecule magnets (SMMs). The bistability of SCO materials based on 3d metals (predominantly FeII) has allowed these materials to be proposed for applications in displays, sensors and information storage devices. Similarly, SMMs, which are d- and f-block coordination compounds defined by an effective energy barrier to reversal of their magnetization, have also been suggested for use in information storage devices by virtue of their magnetic bistability.Despite the bistability in SCO compounds and in SMMs, the two phenomena are observed in different temperature regimes; SCO tends to occur in the 50-350 K regime, whereas SMM behaviour usually occurs below 50 K. If systems displaying both phenomena could be obtained, they would provide a route to bifunctional molecular magnets in which the SCO and SMM phenomena influence each other in a synergic way. The first challenge confronting this ambition is that general synthetic routes to SCO-SMM materials are extremely rare: in this project supramolecular architectures consisting of lanthanide SMMs and SCO compounds will be developed in to explore the properties of bifunctional molecular magnets using a novel synthetic methodology. The second challenge will be to understand how the SCO and SMM phenomena influence each other via factors such as magnetic exchange. To achieve this, we will study SCO-SMMs on the molecular and supramolecular (rotaxane) scales, thus allowing through-bond and through-space interactions to be probed, understood and controlled. The following milestones will be achieved:Milestone 1: a general method - based on the reactivity of 'masked' divalent lanthanide reagents - for the synthesis of heterobimetallic Fe-Ln complexes with interdependent SCO and SMM properties.Milestone 2: synthetic route to a unique family of rotaxane molecular magnets - including photoactivated derivatives - in which communication between SCO and SMM subunits is mediated via the guest molecule.Milestone 3: detailed characterization of SCO-SMMs based on a range of physical techniques.Milestone 4: Theoretical understanding of the SCO-SMMs, with an ability to use this understanding to enhance the magnetic properties through controlled synthetic modifications.

从简单的化学构件合成复杂的磁性材料体现了分子磁性的内在魅力。分子磁体通常采用自下而上的方法设计，为配体场理论等理论模型提供实验测试平台。分子方法还使得合理的应用成为可能，例如使用过渡金属配合物作为量子计算的量子位，使用镧系元素配合物作为磁性制冷剂，以及在核磁共振波谱中作为位移试剂和磁共振成像。目前大量的工作集中在分子系统中的磁双稳态现象上，从而可以在相同的物理条件下测量两种不同的磁响应。双稳态分子磁体的两种重要类型是自旋交叉（SCO）化合物和单分子磁体（SMM）。基于 3d 金属（主要是 FeII）的 SCO 材料的双稳定性使得这些材料被提议用于显示器、传感器和信息存储设备。同样，SMM 是 d 和 f 块配位化合物，由其磁化反转的有效能量势垒定义，凭借其磁双稳态性，也被建议用于信息存储设备。尽管 SCO 化合物和 SMM 中存在双稳态，但这两种现象是在不同的温度范围内观察到的； SCO往往发生在50-350 K范围内，而SMM行为通常发生在50 K以下。如果可以获得显示这两种现象的系统，它们将为双功能分子磁体提供一条途径，其中SCO和SMM现象以协同方式相互影响。这一雄心壮志面临的第一个挑战是 SCO-SMM 材料的通用合成路线极其罕见：在该项目中，将开发由镧系元素 SMM 和 SCO 化合物组成的超分子结构，以使用新颖的合成方法探索双功能分子磁体的特性。第二个挑战是了解 SCO 和 SMM 现象如何通过磁交换等因素相互影响。为了实现这一目标，我们将在分子和超分子（轮烷）尺度上研究 SCO-SMM，从而能够探测、理解和控制通过键和通过空间的相互作用。将实现以下里程碑：里程碑 1：基于“掩蔽”二价稀土试剂的反应性的通用方法，用于合成具有相互依赖的 SCO 和 SMM 特性的异双金属 Fe-Ln 配合物。里程碑 2：合成独特的轮烷分子磁体家族（包括光活化衍生物）的路线，其中 SCO 和 SMM 亚基之间的通信是 里程碑 3：基于一系列物理技术对 SCO-SMM 进行详细表征。里程碑 4：对 SCO-SMM 的理论理解，能够利用这种理解通过受控合成修饰来增强磁性。