Northwestern University graduate student Jonathan Barnes had a hunch for creating an exotic new chemical compound, and his idea that the force of love is stronger than hate proved correct. He and his colleagues are the first to permanently interlock two identical tetracationic rings that normally are repelled by each other. Many experts had said it couldn't be done.
On the surface, the rings hate each other because each carries four positive charges (making them tetracationic). But Barnes discovered by introducing radicals (unpaired electrons) onto the scene, the researchers could create a love-hate relationship in which love triumphs.
Unpaired electrons want to pair up and be stable, and it turns out the attraction of one ring's single electrons to the other ring's single electrons is stronger than the repelling forces.
The process links the rings not by a chemical bond but by a mechanical bond, which, once in place, cannot easily be torn asunder.
The study detailing this new class of stable organic radicals will be published Jan. 25 by the journal Science.
"It's not that people have tried and failed to put these two rings together -- they just didn't think it was possible," said Sir Fraser Stoddart, a senior author of the paper. "Now this molecule has been made. I cannot overemphasize Jonathan's achievement -- it is really outside the box. Now we are excited to see where this new chemistry leads us."
Sir Fraser is the Board of Trustees Professor of Chemistry in the Weinberg College of Arts and Sciences at Northwestern. In the late 1980s, he was one of the early pioneers to introduce an additional type of bond, the mechanical bond, into chemical compounds.
The new Northwestern compound has attractive electronic characteristics and can be made quickly and inexpensively. Down the road, it may be possible to expand this first linked pair into a longer chain-like polymer where this methodolog
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