GAS-PHASE SELF-ASSEMBLY OF ENDOHEDRAL METALLOFULLERENES

METALLOFULLERENES1,2 consist of metal atoms trapped inside closed full erene cages. Virtually nothing is known about the mechanism of metallo fullerene synthesis, although the possibility of a condensed-phase mec hanism has been suggested in recent studies3,4. Here we show that lase r vaporization of a La2O3/graphite rod produces a number of LaC60+ iso mers, including the endohedral metallofullerene and a variety of diffe rent isomers in which lanthanum seems to be bound to polycyclic polyyn e rings. When heated, nearly all of the different ring isomers convert spontaneously into metallofullerenes, trapping the metal atom inside the fullerene cage with remarkably high efficiency (>98%). We suggest that in the first step of this annealing process the lanthanum atom ac ts as a nucleation centre and the carbon rings arrange themselves arou nd the lanthanum atom before converting into a fullerene cage.