Fullerenes (endohedral fullerenes, endofullerene cluster)
The Discovery of the Fullerenes
A characteristic absorption line at 210 nm in the horse head nebula lead 1985 to the discovery of the fullerenes by Prof. Sir H.W. Kroto, Prof. R.E. Smalley, Prof. R.F. Curl
For their discovery the scientists were awarded the Nobel prize in chemistry in 1996
60 carbon atoms, 20 hexagons, 12 pentagons, molecular symmetry, Ih, crystal symmetry: Fm3m
diameter: 0.7 nm (atomic) 1.1 nm (V.d. Waals)
| HOMO : t1u | 46 vibrational modes |
| LUMO : hu | 10 Raman activ |
| hu - t1u : 2 eV, forbidden | 4 IR activ |
| hu - t1g : 2.6 eV, allowed |
Fullerene Doping and Fullerene Salts
Fullerene doping
By intercalation of electron donors Superconductivity up to Tc= 30 K
Determination of charge transfer from pentagonal pinch mode Raman line: 6.5 e/cm-1
TDAE+ C60-crystals
Tetrakis (dimethyl-amino)ethylene C2N4(CH3)8, Soft ferromagnet with Tc = 16 KPolymeric Fullerenes, Heterofullerenes
Fulleren polymerization
Polymerization is induced by cycloaddition or by single bonds between two carbons on the cages, by doping, by pressure or by irradiationOne-dimensional polymers
C60, (K,RB)C60
C70
Pressure polymer
Na4C60
Dimerization
(C59N)2
Stability of polymeric fullerenes, S. Pekker et al., 2000
Chemical Functionalization of Fullerenes
Fullerenes with adduct groups
Water solubility, Application in pharmacy and medicin
Dendrimer
Water soluble fullerenes as HIV inhibitor
S.H. Friedman et al., JACS 115, 6506 (1993)
Higher Fullerenes and Endohedral Fullerenes
Euler‘s polyeder rule: C – E + F = 2
The number of corners C minus the number of edges E plus the number of faces F equals 2In pristine and empty cages the pentagons must be isolated
C78: 5 isolated pentagon isomeres - 3 have been identified
Sc2@ C84
The metal-cage modes split in the crystal field
Sc2C2@ C84
Due to its low symmetry the cage of C84 has 256 Ramanactive modes
At low temperature the C2 unit rotates free around the Sc-Sc axis. This configuration represents a gyroscope with quantized rotations