Atom-by-atom control for the targeted chemical synthesis of heterometallic molecular nanomagnets

目前的磁性材料是采用“自上而下”的方法制造的。颗粒的随机分布散布在硬盘驱动器表面上：介质本身没有任何特征，而写头定义了位的位置。这些磁性颗粒(颗粒)不能无限期地继续减小尺寸，因为热能将变得足以反转磁域的磁化，从而导致数据丢失。因此，开发新型磁性材料势在必行。如果比特的尺寸进一步减小到几纳米，我们就进入了磁性分子的领域，这种分子容易合成，价格低廉，而且是单分散的，允许在表面上自组装一系列分子比特。然而，目前合成这些磁性分子的方法在很大程度上依赖于含有有机配体的反应混合物中过渡金属离子的随机组装。这种方法对反应产物的合成控制很少，因此对生成的分子的磁性几乎没有控制。因此，这些磁性分子只有在非常低的温度下才会显示出它们有趣的性质。为了提高所谓的封闭温度，我们需要更好地控制它们的合成。我们将使用一种逐步自组装的合成方法来制备改进的分子纳米磁体(单分子磁体或SMM)。我们将使用质谱仪，从精心设计的前体开始，追踪这些分子在溶液中的组装情况。这项技术将使我们能够控制异金属络合物的合成，这将包含两到四种不同类型的磁性离子。我们将能够精确地控制每种类型的离子在磁性分子中的位置，例如产生核壳结构。这种综合控制水平将允许我们既控制磁交换耦合又控制磁各向异性。这种令人难以置信的对关键磁性特性的控制水平将使我们能够合成具有前所未有的结构和阻挡温度的单分子磁体，超过目前的世界纪录。

Current magnetic materials are made using a 'top-down' approach. A random distribution of grains is dispersed across the hard drive surface: the media itself is featureless and the write head defines the bit locations. These magnetic particles (grains) cannot continue to decrease in size indefinitely as the thermal energy will become sufficient to flip the magnetisation of the magnetic domain, leading to data loss. Therefore, it is imperative that new magnetic materials are developed. If the bit size is to decrease further towards a few nanometres, we move into the realm of magnetic molecules, which are easy to synthesise, cheap and are monodisperse, allowing for self-assembly of an array of molecular bits on a surface. However, current synthetic approaches to these magnetic molecules rely heavily upon the random assembly of transition metal ions from a reaction mixture containing organic ligands. This method affords little synthetic control over the reaction product and hence, little control over the resultant magnetic properties of the molecule. Therefore, these magnetic molecules display their interesting properties only at very low temperatures. To increase the so-called blocking temperature, we need much greater control over their synthesis.We will use a step-by-step self-assembly synthetic approach to prepare improved molecular nanomagnets (single-molecule magnets or SMMs). We will track the assembly of these molecules in solution, from their carefully designed precursors, using mass spectrometry. This technique will allow us to control the synthesis of heterometallic complexes, which will contain between two and four different types of magnetic ions. We will be able to control exactly where each type of ion resides within the magnetic molecule, e.g. producing core-shell structures. This level of synthetic control will allow us to control both the magnetic exchange coupling and the magnetic anisotropy. This incredible level of control over the key magnetic properties will allow us to synthesise single-molecule magnets with unprecedented structures and blocking temperatures that surpass the current world record.