A Hint Of Carbyne

Thanks to bulky end-capping groups, researchers have come closer than ever to synthesizing the lesser known carbon allotrope carbyne, which is made of extremely long chains of alternating single and triple bonds. Carbon allotropes such as nanotubes and graphene—the latest darlings of materials science—are prompting chemists to try to isolate carbyne and determine its properties, too. Carbyne is thought to exist in interstellar dust and meteorites, but attempts to make it have led to ill-defined materials. Attempts to model carbyne by synthesizing polyalkyne chains have been somewhat successful, with a 28-carbon chain being the longest isolable polyyne reported. Rik R. Tykwinski (now at Germany’s Friedrich-Alexander University) and Wesley A. Chalifoux of the University of Alberta have now made polyynes that are up to 44 carbons long, stabilizing the chains with sterically hindered groups that sit like ten-gallon hats on the chain ends (Nat. Chem., DOI: 10.1038/nchem.828). As the polyynes get longer, the electronic bandgap appears to approach a value different from previous estimates made with shorter alkyne chains, they note. Because the long polyyne can be handled under normal laboratory conditions, the researchers think that carbyne itself may be within reach.