Preparation and Characterization of Fulleroid and Methanofullerene Derivatives

We describe the synthesis and complete characterization of soluble derivatives of C-60 for applications to physics and biology. The goal of the strategy was to have a ''modular'' approach in order to be able to easily vary a functional group attached indirectly to the cluster. The functionality could be hydrophilic (e.g., histamide) or hydrophobic (e.g., cholestanoxy). The former was prepared for biological studies and the latter for photophysical studies toward improvement of photoinduced electron transfer efficiencies in the fabrication of photodetectors and photodiodes. An important intermediate, a carboxylic acid, was found to be recalcitrant to characterization by the usual mass spectroscopic and elemental analysis techniques. This problem was solved by the use of MALDIMS. The carboxylic acid was easily converted to the key intermediate acid chloride, which in turn was convertible to a large variety of derivatives. Both isomeric forms ([5,6], fulleroid and [6,6], methanofullerene) of the C-61 clusters were prepared. The fulleroid formation could have given rise to a 50:50 mixture of phenyl-over-former pentagon phenyl-over-former hexagon isomers but, remarkably, afforded a 95:5 mixture of these isomers, respectively. The fulleroid and methano-fullerene gave different cyclic voltammograms, with the former being reduced at 34 mV more positive potential than the latter.