... And self-assembling chemical parts.

. . . and self-assembling chemical parts

Sicily once was known was Trinacria, a name legendarily ascribed to the island's three-pointed shape. Trinacria's emblem -- a human head with three legs fanning out symmetrically like a pinwheel -- reflected this configuration. Now, British and Italian researchers say they have assembled a large, three-pronged molecule that resembles Trinacria's emblem, using a powerful new strategy of chemical synthesis. They call the molecule trinacrene.

In the September international edition of the West German journal ANGEWANDTE CHEMIE, the researchers describe the procedure, known as structure-directed synthesis, as a sort of "precision molecular LEGO," in which selected molecular pieces snap together according to the chemical constraints, or "pegs," inherent in those pieces. Chemists J. Fraser Stoddart and Peter R. Ashton of the University of Sheffield and co-workers at the University of Whiteknights in Reading and the University of Messina, Italy, report making trinacrene in two steps using two readily available starting chemicals. One chemical, called a bisdiene, contains several sets of double bonds, each of which could free up a bond for lingking with an appropriate chemical suitor. With three lobes that can each react with available bonds, the other cloverleaf-shaped reactant makes a perfect suitor.

In the first step of the reaction, separate bisdiene molecules connect to each lobe of the cloverleaf molecule to form an open, three-pronged intermediate. This leaves each bent prong tipped with a pair of double bonds, creating a structure strategically arranged to accept another cloverleaf component. In the second and final step, the researchers add more of the cloverleaf-shaped reactant to the intermediate to cap the awaiting prongs.