Organic approaches to endohedral metallofullerenes: Cracking open or zipping up carbon shells?

We have been investigating the synthesis of endohedral metallofullerenes since we successfully opened an orifice on the framework of C-60 in the form of a cobalt complex having the metal sitting on top of the opening. A second approach aims at the synthesis of spherically-shaped acetylenic macrocycles, which are expected to rearrange to endohedral metal complexes of fullerenes in a controlled process analogous to the gas-phase coalescence of mono- and polycyclic polyynes during fullerene formation by the graphite evaporation method. Since the potential benefits from obtaining endohedral metal complexes of C-60 are enormous, both approaches are being actively pursued in our group.