REDOX PROPERTIES OF ORGANOFULLERENES

A comparative study using cyclic, differential pulse, and Osteryoung square wave voltammetry is presented on organofullerenes derivatized with oxygen-, carbon-, and silicon-containing groups. Electron affinities of the organofullerenes increase with increasing electronegativities of the attached atoms. C60O is a stronger electron acceptor than C-60, although its electroreductions are CV irreversible. In the carbon-derivatized C-60, hybridization of the attached carbon atoms and electron-withdrawing groups also affect their reduction potentials. As previously described for C-60, no CV reversible electrooxidation waves were observed for all organofullerenes studied. Electron-donating groups, such as alkyl and silyl, significantly lower the oxidation potentials of the organofullerenes. The AM1 molecular orbital calculations were performed on C-60 and selected organofullerenes. The first and second reduction potentials correlate well with the LUMO energy levels, while the third reduction potentials correlate better with the LUMO+1 energy levels. The peak oxidation potentials also show a good linear correlation with the HOMO energy levels.