Fullerene Electrochemistry

More than ten years after the initial isolation of gram-quantities of fullerene compounds in 1990 [1], the field has matured considerably but continues to evolve in new and interesting directions. The unique properties of fullerenes and their derivatives continue to find applications in potentially useful areas, some of which are reviewed in other chapters in this book. Some of the properties that caught a lot of the initial attention in fullerene research, such as superconductivity [2], have found renewed interest in view of very recent observations of increased critical temperature or T_C values in hole-doped C₆₀ [3]. At the time of writing of this article a new report has appeared describing the use of bromoform to expand the crystal lattice of C₆₀ and the consequent observation of superconductivity at 117 K for hole-doped single crystals of this material [4]. This is the highest transition temperature ever observed for a non-cuprate superconductor and qualifies the fullerenes as the second class of materials that have broken the 77 K T_c barrier. Due to the greater ease of processability compared to the corresponding cuprate ceramics, it is possible that these C₆₀-based superconductors will catch up and maybe surpass the ceramic materials in technological applications. Perhaps more interestingly, the work reported suggests that further expansion of the lattice parameter from the observed 14.45 Å for the bromoform-based material to 14.7 Å without breaking the crystal could result in superconductivity around room temperature.