Chemistry of open-shell correlated materials based on unsaturated hydrocarbons

这是一个长期的基础研究项目，目标是合成一种新的晶体材料家族，其化学、电子和磁性能将为基础科学创造机会。迄今为止，这种进步主要是在无机材料方面取得的。这个项目将把这种机会扩展到电子活性成分是有机阴离子的材料。我们对硅和铜等材料的理解依赖于对电子的描述，在这些电子中，它们彼此之间没有强烈的相互作用。电子相互作用强烈的材料的电子行为，被称为相关材料，不同于这些经典的自由电子材料。相关材料已经成为新的电子和磁性基态和性质的丰富来源。由于无机固体材料化学提供了定位多个不同金属阳离子的能力，因此可以预测自旋、轨道和电荷的排列，因此这种行为在无机系统中已经被大量观察到。我们没有这样的合成能力，也没有对有机相关电子材料的晶体化学理解。一个成功的例子是像K3C60这样的富勒化物超导体，其潜在的晶体化学是基于球体填充的，直接类似于经过充分研究的无机系统，可以进行广泛的合成控制和性能设计。虽然目前提供了一系列出色的性能，但全无机系统仅限于元素周期表提供的原子，其晶体和电子结构由这些元素的离子大小和轨道特征控制。如果我们能够实现类似的基于电子活性有机物质的结构的一般控制，例如通过还原本文研究的不饱和分子衍生的阴离子，则所得的结构和电子性质将由分子的大小，形状和电子结构决定。与无机离子系统相比，有机分子的这些空间和电子结构是这些材料的基本组成部分，它们是由合成化学控制的。在最近发表在《自然化学》上的两篇论文中，我们报道了化学合成方法，可以产生还原不饱和芳香分子的结晶盐，并获得新的电子态，包括三维pi电子基材料中量子自旋液体基态的候选物。这一进展表明，在富勒化物之外，有可能创造出一系列可调谐的晶体有机电子材料。该项目将建立这一家族，允许定位电子和立体可调谐的构建块，以控制电子、磁性、光学和电荷存储特性。这将通过发展合成化学能力来实现，从广泛的不饱和有机分子中生产结晶材料。为了产生与无机系统具有相当成分和结构复杂性的材料，我们将应用并扩展这种化学到具有多个金属位点和多个分子成分的材料中。这将允许我们通过分子单元之间的定位和电荷转移来控制扩展的电子结构，以目标几何受挫的磁晶格和量子自旋液体中的移动电荷为例，作为这种化学将实现的新电子基态的例子。所得烃类盐的组成、电荷态和结构将揭示该类材料的电荷存储潜力。我们将使用信息学技术来指导对化学空间的有效探索，并与我们的国际合作者一起应用一系列结构、热力学、光谱、电子和磁测量技术来识别出现的新电子态。

This is a long-range basic research project that targets the synthesis of a new crystalline materials family whose chemical, electronic and magnetic properties will create opportunities in fundamental science. To date, such advances have mainly been made in inorganic materials. This project will extend that opportunity to materials where the electronically active component is an organic anion.Our understanding of materials such as silicon and copper relies on a description of the electrons in which they do not interact strongly with each other. The electronic behaviour of materials in which the electrons do interact strongly, known as correlated materials, differs from such classical free electron materials. Correlated materials have been a fruitful source of new electronic and magnetic ground states and properties. This behaviour has overwhelmingly been observed in inorganic systems, because of the capability offered by inorganic solid state materials chemistry to position multiple distinct metal cations and thus predictably arrange spins, orbitals and charges. We have no such synthetic capability or crystal chemical understanding for organic correlated electron materials. The one example of success is the fulleride superconductors such as K3C60, where the underlying crystal chemistry is based on sphere packing that is directly analogous to well-studied inorganic systems, enabling extensive synthetic control and property design.While currently offering an outstanding range of properties, all-inorganic systems are restricted to the atoms provided by the periodic table, whose crystal and electronic structures are controlled by the ionic size and orbital characteristics of those elements. If we could achieve similar general control of structures based on electronically active organic species, such as anions derived by reduction of unsaturated molecules studied here, the resulting structural and electronic properties would be determined by the molecular size, shape and electronic structure. In contrast to the inorganic ionic systems, these steric and electronic structures of the organic molecules that would be the building blocks of such materials are controllable by synthetic chemistry.In two recent papers in Nature Chemistry, we have reported chemical synthesis approaches that produce crystalline salts of reduced unsaturated aromatic molecules and access new electronic states, including a candidate for the quantum spin liquid ground state in a three-dimensional pi-electron based material. This advance demonstrates the potential to create a family of tuneable crystalline organic electronic materials beyond the fullerides. The project will establish this family, allowing the positioning of electronically and sterically tuneable building blocks to control electronic, magnetic, optical and charge storage properties.This will be achieved by developing the synthetic chemistry capability to produce crystalline materials from a broad range of unsaturated organic molecules. To generate materials of comparable compositional and structural complexity to the inorganic systems, we will apply and expand this chemistry to materials with multiple metal sites and with more than one molecular component. This will allow us to control extended electronic structure by positioning of and charge transfer between the molecular units to target geometrically frustrated magnetic lattices and mobile charges in quantum spin liquids as examples of the new electronic ground states this chemistry will enable. The compositions, charge states and structures of the resulting hydrocarbon salts will reveal the charge storage potential of this family of materials.We will use informatics techniques to guide efficient exploration of the chemical space, and apply a range of structural, thermodynamic, spectroscopic, electronic and magnetic measurement techniques with our international collaborators to identify the new electronic states that arise.