Chemistry of open-shell correlated materials based on unsaturated hydrocarbons

点击翻译按钮获取中文摘要

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.