Dynamics of paramagnetic metallofullerenes in carbon nanotube peapods

We filled SWNTs with the paramagnetic fullerene Sc@C-82 to form peapods. The interfullerene 1D packing distance measured using TEM is d = 1.1 +/- 0.02 nm. The SC@C-82 in SWNT peapods continuously rotated during the 2 s TEM exposure time, and we did not see the Sc atoms. However, SC@C-82 metallofullerenes in MWNT peapods have periods of fixed orientation, indicated by the brief observation of Sc atoms. La@C-82 peapods were also prepared and their rotational behavior examined. The interfullerene 1D packing of both La@C-82 and SC@C-82 peapods is identical and thus independent of the charge transfer state for these paramagnetic fullerenes. The La@C-82 metallofullerenes in the peapods have fixed orientations for extended periods of time, up to 50 s in some cases. The La@C-82 spontaneously rotates rapidly between fixed orientations.