New function inside the fullerene cage

Redoxreaktion des Fullerens erstmalig über das eingeschlossene Metall steuerbar

Die Autoren (v.r.n.l.) Alexey Popov, Lothar Dunsch und Shangfeng Yang. (Foto: IFW Dresden)

Researchers from IFW Dresden and University of Heifei can tune the electronic state in "endohedral" fullerenes for the first time. The technique could come in useful for studying spin transport in nanoscale devices.

Fullerenes are cage-shaped molecules consisting of carbon. The fullerene occurring most frequently - C60 – consists of 60 carbon atoms forming a cage of only 0.71 nanometer in diameter. If the cage encloses other atoms, ions or molecules they are called endohedral fullerenes.

In the recent years among the endohedral fullerenes (fullerenes with an encaged species) the nitride clusterfullerenes M₃N@C_2n have found large interest due to their high stability and their large variety of cluster composition. Researchers of IFW Dresden and the University of Hefei have now found that if one metal in nitride clusterfullerenes M₃N@C_2n is a transition metal (e.g., titanium), the spin density of electrons is localized on this metal. By varying the redox state of the whole molecule (via electrochemistry as in this work), the oxidation state of the titanium atom can actually be changed. This is the first endohedral fullerene in which redox activity is exclusively due to the encaged metal atoms. In most other cases, the fullerene cage itself is responsible for redox activity. Thus the electronic state of endohedral species in fullerenes could now be precisely tuned. Moreover, since the endohedral cluster must be rotating inside the fullerene cage, this leads to the very flexible electron spin density distribution in TiSc₂N@C₈₀ i.e. the spin density distribution also changes quickly. This effect which we have dubbed "spin flow" enables us to follow the spin populations using molecular dynamics simulations and to obtain a 'spin-flow vibrational spectrum' that clearly shows what kinds of internal motion are coupled to the spin flow. In fact, all types of molecules – not just endohedral metallofullerenes – might be studied using this technique.

The importance has been reviewed by a British nanotechnology journal. Online:

Online: http://nanotechweb.org/cws/article/tech/43535

Contact:

Dr. Alexey Popov

a.popov@ifw-dresden.de

Tel. 0351-4659658

Prof. Dr. Lothar Dunsch

l.dunsch@ifw-dresden.de