High Symmetry Paramagnetic Cages

Molecular compounds containing lots of (para)magnetic transition metal ions ( cage complexes ) can display fascinating and fundamentally important magnetic properties. They have allowed detailed insight into, for example, quantum size effects in magnets with direct relevance to possible future technologies including quantum computing and molecular spintronics. Such molecular cages are conventionally made by standard coordination chemistry techniques. The groups at Manchester and Edinburgh involved in this proposal have developed synthetic routes to such materials by non-standard methods, namely solvothermal (akin to a pressure cooker) and microwave methods. These very different (in temperature, pressure and timescale regimes) reaction conditions can lead to very different chemistry. We have observed that the forcing conditions often result in high symmetry cages. This high symmetry can lead to very unusual magnetic phenomena: for example, we have found molecular materials that display enormous low temperature magnetocaloric effects (temperature changes on changing a magnetic field) and also memory effects to unusually high temperature by a previously unobserved mechanism. This proposal seeks to build on these observations by systematically investigating the use of forcing conditions in the synthesis of high symmetry, high nuclearity d-block, f-block (rare earth) and d-f hybrid transition metal cages. We will examine the relationship between solvothermal and microwave heating, cage symmetry and magnetic properties. We expect to find unusual and potentially useful low temperature physics, resulting from highly frustrated spin topologies, including enhanced magnetocaloric effects, as well as other effects that have been predicted but as yet unobserved for cages based on Platonic and Archimedian solids.