New project to study molecular magnets funded by The Leverhulme Trust | School of Chemistry

The project “Stellated Archimedean and Keplerate Polyhedra: Frustrated Molecular Magnets” will be led by the School of Chemistry’s Professor Euan Brechin.

The aim of the project is to build and characterise high symmetry, spin frustrated, molecular cages of paramagnetic 3d transition metal ions with structures conforming to Stellated Archimedean and Keplerate polyhedra using calix[n]arene building blocks. Such species represent ideal molecules for examining geometric spin frustration since they consist of very high symmetry polyhedra possessing odd and even numbered faces which prevent the preferred antiparallel alignment of antiferromagnetically coupled spins. For example, spins on an equilateral triangle cannot all be simulataneously antiparallel to one another.

The effects of spin frustration on the energy spectrum and magnetic properties of molecular coordination compounds are fascinating and include enhanced ground-state degeneracy, low-lying singlet states, non-collinear ground states, unusual magnetisation plateaus and jumps, and attractive magnetocaloric properties. This makes them both academically interesting and potentially useful for applications in, for example, cryogenic refrigeration.

The project is a collaborative effort between Euan Brechin (Chemistry, UoE), Scott Dalgarno (Chemistry, Heriot-Watt) and Chris Stock (Physics, UoE). Brechin, Dalgarno, Stock have successfully collaborated for many years, and proof-of-principle results obtained in the past couple of years underpinned this successful grant application, including their 2024 paper “Stellated Cuboctahedron of Fe(III)”, published as a “Hot Paper” in Angewandte Chemistry International Edition.

The project will combine synthetic organic and inorganic chemistry, X-ray crystallography, magnetometry, heat capacity and neutron scattering involving the three researchers in Edinburgh and an international network of collaborators. It will make use of the School of Chemistry’s in-house characterisation including single crystal and powder XRD, magnetometry and heat capacity, combined with software development and neutron scattering at central facilities in the UK, Europe, Japan and USA.

We are enormously grateful for the funding provided by the Leverhulme Trust that will enable us to make and characterise a new class of molecules that will not only have important academic interest in the field of spin frustration, but potential application in cryogenic refrigeration with a view to the replacement of Helium, a critical raw material.