Scattering&Spectroscopy
Universität Wien

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 K

Polymeric 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 irradiation

One-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 2
In 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