Magnetic Plastics

Cheap, lightweight, non-metallic magnets could result from the discovery of badly behaved electrons in a new type of free radical discovered by US researchers.

Paul Wenthold
Anna Krylov

Paul Wenthold of Purdue University has analyzed a radical hydrocarbon that contains no transition metal but behaves bizarrely, as Wenthold explains. "This material is a unique exception to the electron-behavior rule, and it might help chemists think more clearly about where other exceptions lie," he said. "Designing materials with novel properties depends on understanding the forces at work inside their molecules, and understanding the structure of this exceptional molecule could lead to new tools for material design."

Wenthold collaborated with Anna Krylov of the University of Southern California to deduce the structure of the material using mass spectrometry and other techniques.
 

The radical in question is 5-dehydro-1,3-quinodimethane and has three unpaired electrons that do not arrange themselves in accordance with Hund's Rule, says Wenthold. Hund's rule says that unpaired electrons should line up facing the same direction when they arrange themselves around the molecular center. "However, one of the three unpaired electrons in our molecule faces the opposite direction," Wenthold explained. "Since this is the first time we've ever seen this happen in an organic triradical, it opens up a few new possibilities for materials designers."
 
The materials might, Krylov adds, be used as building blocks for molecular magnets. "People are already trying to build magnets from materials other than metals, such as the polymers," she says. "Since magnetism is related to the behavior of unpaired electrons, this compound could be used as a building block for such polymers, leading to non-metallic magnets."
 

Non-metal magnets would have several advantages over their metallic counterparts, such as being less dense and so useful in applications where weight is a concern.