Professor Keith Murray

There is currently great interest worldwide in synthesising nano- dimensioned magnetic materials of iron and manganese, in particular, so that their magnetic (e.g. 'superparamagnetic' or 'single-molecule magnetism') and novel quantum features can be explored. In the longer term, it is hoped that such materials will provide new and useful memory and information storage devices. There are broadly two approaches being used to prepare such materials, the first of a 'top down' approach starting from mineral-like iron oxides, the second, used here, of the 'bottom-up' type in which soluble iron oxide-organic ligand fragments are crystallised under mild conditions, such that their molecular structures can be probed in detail by X-ray crystallographic methods. In the present paper, we have used a flexible amino-alcohol organic ligand that allows the preferred oxo-iron(III) 'cluster' to form and does not force any particular geometry upon it. Consequently, for the first time, a seven-iron species has been isolated having a millennium-dome (London) shaped structure and displaying five spins in the ground state. While the magnetic features are very interesting, they are not superparamagnetic in nature. An eight-iron cluster was also isolated and showed different structural and magnetic features to the seven-iron compounds.

2. What has motivated you to conduct this work? 

As well as the reasons given above, this work formed part of a broad project looking at new single-molecule magnet (SMM) cluster compounds of iron, manganese and cobalt. The work is supported by a Discovery Grant from the Australian Research Council. A new face in our group was that of co-author Dr Leigh Jones, from Manchester University, who was armed with all the skills and enthusiasm in cluster synthesis gleaned in his PhD project. My own background in iron-oxo chemistry has stretched back to the 1960s. It was enhanced through recent collaborations with colleagues Professors Bruce West and Leone Spiccia, in which new sol-gel approaches to iron-oxo cluster synthesis were employed. Leigh then added his own approaches and motivation to the present work In the broader context, materials chemistry is an area of strength in the Science Faculty at Monash University and thus we are always striving to develop new areas, here dealing with molecular magnetic materials.

3. Where do you see this work developing in the future? 

To date, synthetic work on iron- or manganese -oxide bridged clusters has often suffered from a lack of control in knowing the type of cluster, e.g. small or large, to be isolated. Pleasingly, however, such materials often show fascinating structures and magnetism. Future work will endeavour to try and gain control and design, for instance through careful ligand choice. Recently we have isolated new iron-oxo clusters using polynucleating ligands, that were being employed in a quite separate project. Such ligands force particular binding modes on the metal ions.

4. Are there any particular challenges facing future research in this area? 

From the broader perspective of translating SMM cluster compounds in to useful devices there are many major challenges, not the least being to produce molecular materials that show their 'magnet' properties (stepped hysteresis) at room temperature, possibly by 'stitching' clusters together in to polymeric arrays, but also to learn how to read information from, and send messages to, such nano-scaled molecules. Great strides are being made in the latter area by physicists and materials engineers. Chemists need to catch up!