Polyynes and the Formation of Fullerenes [and Discussion]

The synthesis and microwave study of linear cyanopolyynes, HC$_{5}$N and HC$_{7}$N, in the mid-1970s was followed by the unanticipated detection of these, and longer chains (HC$_{9}$N and HC$_{11}$N), in space. To gain insight into the way in which such species and carbon clusters in general might form, an experiment was devised in 1985 to simulate conditions in carbon stars, involving the laser vaporization of graphite in a supersonic nozzle and detection of the resulting carbon species by mass spectrometry. This initiative resulted in the serendipitious discovery of an entirely new allotrope of carbon, C$_{60}$, named buckminsterfullerene after the inventor of the geodesic dome. Five to seven years later, C$_{60}$ and other members of what is now know as the fullerene family have been isolated in macroscopic amounts, however, these exciting developments have tended to overshadow fundamental problems associated with the aggregation of carbon atoms in which acetylenes, and polyynes in particular, may play a key role.