Garden chemistry

Interlocking pseudorotaxanes and rotaxanes to form a molecular daisy chain is the result of working by Sheng-Hsien Chiu of the National Taiwan University, Taipei and his colleagues. These supramolecular systems represent another iteration towards building molecular electronics devices from the bottom up. Chiu's supra synthesis involves is not quite as simple as threading daisies. In it he passes the "flower head" through a hole in the "stalk" and then expanding the "flower head" to stopper it on to the chain and so far the researchers have created only a two-daisy structure. "The challenge remains to overcome entropy and assemble larger cyclic and acyclic molecular daisy chains," says Chiu. This might involve using stiffer daisies that would disfavor dimerization and lead to longer chains.