High Symmetry Paramagnetic Cages

Lead Research Organisation: University of Manchester
Department Name: Chemistry


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.


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Baker ML (2012) A classification of spin frustration in molecular magnets from a physical study of large odd-numbered-metal, odd electron rings. in Proceedings of the National Academy of Sciences of the United States of America

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Blagg RJ (2011) Single pyramid magnets: Dy5 pyramids with slow magnetic relaxation to 40 K. in Angewandte Chemie (International ed. in English)

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Sharples JW (2011) Lanthanide discs chill well and relax slowly. in Chemical communications (Cambridge, England)

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Zheng YZ (2012) Co-Ln mixed-metal phosphonate grids and cages as molecular magnetic refrigerants. in Journal of the American Chemical Society

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Zheng YZ (2012) Mn(II) -Gd(III) phosphonate cages with a large magnetocaloric effect. in Chemistry (Weinheim an der Bergstrasse, Germany)

Description We have made several new simple rare earth compounds where the magnetic relaxation is very slow - the basis of a memory effect - up to record high temperatures. Further and current work is exploring the relaxation mechanisms and how to control these effects. Other aspects of the project are showing enhanced magnetocaloric (magnetic cooling) effects in molecular materials, allowing materials manipulation in a way that is not possible with non-molecular materials. We have recently published the first experimental realisation of this (sub-Kelvin cooling via adiabatic demagnetisation) with a molecular nano magnet.
Exploitation Route The MCE effect can be exploited for very low temperature refrigeration technologies. The materials we are making could hopefully supplant some current conventional methods, e.g. based on expensive and rare 3He. Rare earth materials have promise for exploitation in new molecular technologies, e.g. spintronics.
Sectors Digital/Communication/Information Technologies (including Software),Electronics

Description This was fundamental research in chemistry and physics and its immediate impact has been in the academic sector. The work is now attracting media attention.