Introduction
A Short introduction to fullerenes, their properties and nomenclature
What are fullerenes?
Chemical and physical properties
Introduction
The fullerene era in chemistry essentially began in 1985 following a series of Nobel Prize (1996) winning experiments by Smalley, Kroto, Curl and co-workers [1]. As the new group of molecular allotropes of carbon, fullerenes have been the group of the most investigated molecules of the past century despite of their young history.Discrepant to the two other well-known allotropes of carbon, graphite and diamond, fullerenes are spherical molecules that are attached to each other only by Van der Waals forces in the solid state [2]. Fullfilling the EULER's theorem, fullerene is a polyeder built up by pentagons and hexagons. To form a closed spherical structure, fullerene has to contain exactly 12 pentagons. Following this rule, the smallest possible fullerene has 20 carbon atoms. While the early theoretical investigation showed that only fullerenes with isolated pentagons are stable. Pursuant to this isolated-pentagon-rule (IPR), the smallest stable fullerene should be C60 (left figure) which was experimentally isolated in 1985 and is the most abundant fullerene till now. The next stable homologue IPR-obeying fullerene is C70 (right figure) which is shaped like a rugby ball.
| C60 ("Buckminsterfullerene") | C70 |
Fullerenes are also found in the natural environment, but only in the ppm-range. Some places are Shunga/Russia [3], New Zealand [4] and Sudbury/Canada [6].
Chemical and physical properties
The carbon atoms in fullerenes are in sp2 or sp3 hybridization state. The free valence elctrons on the cage building a strong localized π-electron system. This π-electron system influences chemical reactions of the fullerenes. In chemical reactions fullerenes are not reacting aromatic ("superbenzene"), they show aliphatic behavior.
Good solvents for fullerenes are CS2, o-dichlorobenzene, toluene and xylene [7, 8, 9]. Fullerenes are unsoluble in water and stabil at air. Thin layers of fullerenes are coloured from yellow to yellow-green. Because of π-π* electron transitions solutions of fullerenes are coloured [10]:
- C60 purple/violetred
- C70 brick-red
- C76 light yellow-green
- C2v-C78 maroon, D3-C78 golden,
- C84 brown and
- C86 olive-green.
Species of fullerenes
The following species of fullerenes are known:- (empty) fullerenes ,
- fullerites [11] ,
- fullerides [11] ,
- endohedral fullerenes ,
- exohedral fullerenes ,
- heterofullerenes [12, 13] ,
- metcars.
Term and nomenclature
The name of this new class of structures is in memory to the american inventor, architect and philosopher Richard Buckminster Fuller (1895 - 1993). As architect he designed constructions, builded up from pentagons ans hexagons, for instance the american pavillon on the Expo ‘67 in Montréal.By using the IUPAC-nomenclature the name of C60 is the following:
Hentriacontacyclo[29.29.0.0.2,14.03,12. 04,59.05,10.06,58. 07,55.08,53.09,21. 011,20.013,18.015,30. 016,28.017,25.019,24.022,52. 023.50.026,49.027,47. 029,45.032,44.033,60. 034,57.035,43.036,56. 037,41.038,54.039,51. 040,48.042,46]hexaconta-1,3,5(10),6,8,11,13(18), 14,16,19,21,23,25,27,29(45),30,32(44),33,35(43), 36,38(54),39(51),40(48),41,46,49,52,55,57,59-triacontaene [14].
Because of the difficuties in using this name the structures are called simple "fullerenes".
Contact
Prof. Lothar Dunsch
| Address: | IFW Dresden |
| Helmholtzstraße 20 01069 Dresden |
|
| Germany | |
| Phone: | +49 351 4659 660 |
| Fax: | +49 351 4659 811 |
| Email: | L.Dunsch@ifw-dresden.de |