fullerene
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and cylindrical ones are called carbon nanotubes or buckytubes. Fullerenes are similar in structure to graphite, which is composed of stacked graphene sheets of linked hexagonal rings; but they may also contain pentagonal (or sometimes heptagonal) rings.
The first fullerene to be discovered, and the family's namesake, was buckminsterfullerene (C60), prepared in 1985 by Richard Smalley, Robert Curl, James Heath, Sean O'Brien, and Harold Kroto at Rice University. The name was an homage to Richard Buckminster Fuller, whose geodesic domes it resembles. Fullerenes have since been found to occur (if rarely) in nature.[1]
The discovery of fullerenes greatly expanded the number of known carbon allotropes, which until recently were limited to graphite, diamond, and amorphous carbon such as soot and charcoal. Buckyballs and buckytubes have been the subject of intense research, both for their unique chemistry and for their technological applications, especially in materials science, electronics, and nanotechnology.
Prediction and discovery
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Icosahedral C60H60 cage was mentioned in 1965 as a possible topological structure.[2] The existence of C60 was predicted by Eiji Osawa of Toyohashi University of Technology in 1970.[3][4] He noticed that the structure of a corannulene molecule was a subset of a soccer-ball shape, and he hypothesised that a full ball shape could also exist. His idea was reported in Japanese magazines, but did not reach Europe or the Americas.
Also in 1970, R. W.Henson (then of the Atomic Energy Research Establishment) proposed the structure and made a model of C60. The evidence for this new form of carbon was very weak and was not accepted, even by his colleagues. The results were never published but were acknowledged in Carbon in 1999.[5][6]
With mass spectrometry, discrete peaks were observed corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. In 1985, Harold Kroto (then of the University of Sussex), James R. Heath, Sean O'Brien, Robert Curl and Richard Smalley, from Rice University, discovered C60, and shortly thereafter came to discover the fullerenes.[7] Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of compounds. C60 and other fullerenes were later noticed occurring outside the laboratory (e.g., in normal candle soot). By 1991, it was relatively easy to produce gram-sized samples of fullerene powder using the techniques of Donald Huffman and Wolfgang Krätschmer. Fullerene purification remains a challenge to chemists and to a large extent determines fullerene prices. So-called endohedral fullerenes have ions or small molecules incorporated inside the cage atoms. Fullerene is an unusual reactant in many organic reactions such as the Bingel reaction discovered in 1993. The first nanotubes were obtained in 1991.[8]
Minute quantities of the fullerenes, in the form of C60, C70, C76, and C84 molecules, are produced in nature, hidden in soot and formed by lightning discharges in the atmosphere.[9] In 1992, fullerenes were found in a family of minerals known as Shungites in Karelia, Russia.[1] In 2010, fullerenes have been discovered in space (see Examples in nature).
Naming
Buckminsterfullerene (C60) was named after Richard Buckminster Fuller, a noted architectural modeler who popularized the geodesic dome. Since buckminsterfullerenes have a similar shape to that sort of dome, the name was thought to be appropriate. As the discovery of the fullerene family came after buckminsterfullerene, the shortened name 'fullerene' was used to refer to the family of fullerenes. The suffix “ene” indicates that each C atom is covalently bonded to three others (instead of the maximum of four), a situation that classically would correspond to the existence of bonds involving two pairs of electrons (“double bonds”).
Variations
Since the discovery of fullerenes in 1985, structural variations on fullerenes have evolved well beyond the individual clusters themselves. Examples include:[10]
* buckyball clusters: smallest member is C20 (unsaturated version of dodecahedrane) and the most common is C60;
* nanotubes: hollow tubes of very small dimensions, having single or multiple walls; potential applications in electronics industry;
* megatubes: larger in diameter than nanotubes and prepared with walls of different thickness; potentially used for the transport of a variety of molecules of different sizes;[11]
* polymers: chain, two-dimensional and three-dimensional polymers are formed under high pressure high temperature conditions
* nano"onions": spherical particles based on multiple carbon layers surrounding a buckyball core; proposed for lubricants;[12]
* linked "ball-and-chain" dimers: two buckyballs linked by a carbon chain;[13]
* fullerene rings.
fullerene
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