SIMPLE molecules that 鈥渞ecognise鈥� each other can spontaneously link up and form an interwoven mesh, say a team of chemists. This trick, which mimics many biological processes, could be harnessed to make a vast range of designer chemicals.
Fraser Stoddart and Matthew Fyfe of Birmingham University and their colleagues interwove molecules using a process from 鈥渟upramolecular鈥� chemistry. Here chemists rely on the fact that some molecules join up like pieces of a jigsaw, just as two single strands of DNA join to form a double helix only if matching pairs of bases are in suitable positions to link up.
Chemists have already made self-assembling molecules that use one kind of recognition site, or 鈥渕otif鈥�. For instance, several years ago, Stoddart and his colleagues managed to thread ring-shaped molecules onto strand-like molecules (快猫短视频, Science, 14 March 1992, p 18). This happened spontaneously because negatively charged oxygen atoms on the rings are attracted to positive ions on the strands.
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Now the researchers have taken the process further. 鈥淲e are now mixing the motifs to create more intricate designer materials,鈥� says Stoddart. Making use of two types of molecular recognition, they have encouraged molecules to interlace to form a 鈥渨oven鈥� polymer.
They started with ring-like molecules called crown ethers, which they threaded onto strands containing a positively charged ammonium ion carrying two carboxyl (COOH) groups. They mixed the two components in solution and let the solvent slowly evaporate. Within days, crystals of a supermolecule formed. The team reports in the latest issue of Angewandte Chemie (vol 36, p 735) that the carboxyl groups on the ends of the 鈥渢hreads鈥� locked together as hydrogen bonds formed between them.
According to supramolecular chemist Ed Constable of the Institute of Inorganic Chemistry in Basel, Switzerland, this technique takes chemists one step further towards reproducing the ingenious chemistry of nature. 鈥淏iological molecules are assembled making use of myriad different recognition events,鈥� he says. 鈥淐hemists are learning from biology.鈥�
