February 2, 2004
‘Rule-breaking’ molecule could lead to non-metal magnets
WEST LAFAYETTE, Ind. – Purdue University scientists have uncovered an unusual material that could lead to non-metallic magnets, which might be lighter, cheaper and easier to fabricate than magnets made of metal.
A team of researchers, including Paul G. Wenthold, has analyzed a radical hydrocarbon molecule whose electrons behave differently than they should, according to well-known principles. The compound is not the only molecule that exhibits such odd behavior in its surrounding cloud of electrons, but it is the first to be discovered that does not include a transition metal.
"In that respect, this is a unique exception to the electron-behavior rule, and it might help chemists think more clearly about where other exceptions lie," said Wenthold, an assistant professor of chemistry in Purdue’s School of Science. "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."
The research, which Wenthold conducted with Anna I. Krylov of the University of Southern California and members of both their research groups, appears in today’s (2/ 2) issue of Angewandte Chemie International Edition, a major European chemistry journal. The team deduced the structure of the compound using advanced techniques, including mass spectrometry.
Radical molecules, which contain unpaired electrons and are thus more reactive than molecules without them, have gained household notoriety primarily because so-called "free radicals" in the bloodstream can damage healthy cells. While the molecule Wenthold’s team has investigated is not found in the body and has no household name – it is referred to only by its chemical description, 5-dehydro-1,3-quinodimethane – it has a property that would raise the eyebrows of any observant student in a first-year chemistry course. The surprise stems from the uncommon way its three unpaired electrons arrange themselves around the nuclei in the molecule’s atoms – an arrangement that students learn is virtually fundamental.
"It’s called Hund’s Rule," Wenthold explained. "It says that unpaired electrons line up facing the same direction when they arrange themselves around the molecular center. You might think of them as three-ring binders lying flat on shelves: You want to be able to read the labels on all of their spines, so you lay each binder flat with its spine pointing o
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