Discovery Novel Magnetic Materials
In our research group, Molecular Design & Multifunctional Magnetic Materials Lab, we are exploring Fe(II) and Fe(III) spin crossover systems with designed heterocyclic Schiff base ligands. We tune the electronic and steric properties of the ligand to access materials which show abrupt spin crossover close to room temperature.
Spin Crossover Materials
Fe(II) Spin Crossover
In the case of Fe(II), the ligands we are exploring are based on imidazole and these complexes show spin crossover above, below and at room temperature. In switching from the HS to the LS state the complexes show a dramatic colour change from orange to deep red or purple. The reason for the change in colour is that the gap between t2g and eg* set is larger in the LS state.
Fe(III) Spin Crossover
Iron(III) spin crossover complexes have the advantage of being air stable and are consequently easily developed into future materials. Using principles from crystal engineering we are exploring a new series of designed spin crossover compounds which exhibit abrupt and hysteretic spin crossover.
Structural studies of spin crossover compounds form an essential part of understanding how to design better spin crossover systems. In cases where the structural data of the complex before, during and after spin crossover are available it’s clear that large changes take place at the metal centre.
Single Molecule Magnets
Molecular clusters are molecules containing three or more metal atoms. As well as being of biological interest, many enzymes contain small metal clusters, they can also exhibit fascinating magnetic behaviour.
A family of particular interest are single molecule magnets (SMMs). SMMs exhibit slow relaxation of magnetization and consequently become trapped in one magnetic state. This allows them to be used as molecular switches.
In this area our group has been working Fe and Co clusters with more diverse and designed ligands in an attempt to more effectively control the shape and nuclearity of the clusters.
Spin Crossover Nanomaterials
Nanomaterials are expected to form the basis of technological materials in the future. Nanomaterials developed from our molecular systems allow the design of truly functional devices. These nanomaterials vary in shape from spheres to cubes to rods. Thin films are also accessible and represent a promising alternative to current technology.
Crystal engineering is one of approach that we use to gain more understanding of coordination compound properties. Ligand design is one of the key of success in our group for controlling the inter, intra molecular interactions.