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

目前的磁性材料是使用“自上而下”的方法制造的。随机分布的颗粒分散在硬盘表面：介质本身是无特征的，写入磁头定义了位的位置。这些磁性粒子（晶粒）不能继续无限期地减小尺寸，因为热能将足以翻转磁畴的磁化，导致数据丢失。因此，开发新的磁性材料势在必行。如果比特尺寸进一步减小到几纳米，我们就进入了磁性分子的领域，磁性分子易于合成，价格便宜，并且是单分散的，允许在表面上自组装分子比特阵列。然而，目前这些磁性分子的合成方法严重依赖于从含有有机配体的反应混合物中随机组装过渡金属离子。这种方法对反应产物几乎没有合成控制，因此对分子的合成磁性几乎没有控制。因此，这些磁性分子仅在非常低的温度下才显示出它们有趣的性质。为了提高所谓的阻断温度，我们需要对它们的合成进行更大的控制。我们将使用分步自组装合成方法来制备改进的分子纳米磁体（单分子磁体或SMM）。我们将跟踪这些分子在溶液中的组装，从他们精心设计的前体，使用质谱仪。这项技术将使我们能够控制异金属络合物的合成，这些络合物将包含两种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。这种水平的合成控制将使我们能够控制磁交换耦合和磁各向异性。对关键磁性的这种令人难以置信的控制水平将使我们能够合成具有前所未有的结构和超过当前世界纪录的阻挡温度的单分子磁体。

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.