A family of single molecule magnets (SMMs) with magnetic properties that can be tuned by distorting the molecules have been synthesized by UK researchers. 

Scientists predict that SMMs will form the basis of future high density computer hard disks. They could also be used in quantum computing and magnetic refrigeration. Euan Brechin, at the University of Edinburgh, and colleagues have addressed a limitation in the study of SMMs - how to design specific magnetic behaviour into new molecules. 

 

SMMs on a triangular manganese(III) core have been synthesised with tunable magnetic properties

 

Magnetism occurs when unpaired electron spins in a material align. Brechin based his SMMs on a triangular manganese (III) core ([Mn^III₃O]⁷⁺), which is magnetic because it has unpaired electrons in its normal, low energy state. 

Brechin found that he could change the spin alignment between neighbouring metal ions in oxime-bridged [Mn^III₃O]⁷⁺ clusters from antiferromagnetic (antiparallel spins) to ferromagnetic (parallel spins) by twisting the molecule along the oxime's N-O bond axis. He achieved the twist by changing the ligands attached to the triangular core.  

'This new approach has led to the synthesis of the best performing SMMs known to date,' says Brechin. 'It is perhaps the first step towards real control of molecular structure and physical properties in such systems.'
 

Keith Murray, an expert in molecular magnetic materials at Monash University, Clayton, Australia, is impressed. 'Careful molecular design and skillful syntheses, combined with insightful magnetic, hysteretic and electron paramagnetic resonance studies, have yielded fundamental advances in our understanding of structure-magnetism relations,' he comments. 

Brechin acknowledges that he needs to make more related SMMs to fully understand these systems. 'The same approach could be viable for manipulating the physical properties of the myriad of beautiful molecules already in the literature. This is an exciting prospect,' he states.

James Hodge

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