The unpaired electrons associated with transition metal ions are central to the physical properties (e.g. magnetism and conductivity) associated with many materials utilized in current and future technologies. Our research has exploited the potential of free radicals as alternative spin carriers in the design of new molecule-based materials. Our studies span both the fundamental understanding and control of electron-electron interactions between radicals in the solid state through to their development as new materials with device applications.
Organic Molecular Magnets
Conventional magnetic materials are typically based upon metals and their oxides. However the first examples of organic magnets have only been reported in the last fifteen years. Our own studies have identified several sulfur-nitrogen based radicals (such as those below) which exhibit long range magnetic order in the solid state. We have implemented a wide range of theoretical and physical methods to characterize their magnetic structures and understand the nature of the magnetic communication between radicals in the solid state.
- A. Alberola, R.J. Less, C.M. Pask, J.M. Rawson, F. Palacio, P. Oliete, C. Paulsen, A. Yamaguchi, R.D. Farley and D.M. Murphy, Angew. Chem. Int.Ed. Engl., 2003, 42, 4782. “ Very Important Paper”
- “Spin-Density distribution of p-O2NC6F4CNSSN free radical: PND and ab initio calculations approaches” J. Luzón, J. Campo, F. Palacio, G.J. McIntyre, A.E. Goeta, C.M. Pask and J.M. Rawson. Highlight: 2003 Annual Scientific Report, ILL.
- A. J. Banister, N. Bricklebank, I. Lavender, J. M. Rawson, C. I. Gregory, B. K. Tanner, W. Clegg, M. R. J. Elsegood, F. Palacio, Angew. Chem. 1996, 108, 2648.
- M. Deumal, J.M. Rawson, A.E. Goeta, J.A.K. Howard , R.C.B. Copley , M.A. Robb and J.J. Novoa, Chem. Eur. J. 2010, 16, 2741 - Featured on the front cover and amongst the most accessed articles June 2009 – May 2010.
Many of the paramagnetic radicals prepared in our group tend to associate in solution and in the solid state via a weak p*-p* bonding interaction generating dimeric species. Careful design at the molecular level has allowed us to prepare compounds in which this dimerisation process is reversible in the solid state. In a number of instances these spin-transitions occur at or near room temperature. We are currently looking to exploit this spin-transition behaviour in devices which respond to external stimuli such as heat, light and pressure.
- G.D. McManus, J.M. Rawson, N. Feeder, J. van Duijn, E.J.L. McInnes, J.J. Novoa, R. Burriel, F. Palacio and P. Oliete, J. Mater. Chem., 2001, 11, 1992.
- A. Alberola, R.J. Collis, S.M. Humphrey, R.J. Less and J.M. Rawson, Inorg. Chem., 2006, 45, 1903.