Fullerenides

Fullerenides are a class of chemical compounds derived from fullerenes, which are molecules composed entirely of carbon atoms arranged in a hollow sphere, ellipsoid, or tube. In fullerenides, one or more electrons have been added to the fullerene structure, resulting in a negatively charged fullerene anion. These anions are typically stabilized by counterions, which are positively charged species, often alkali metals like sodium, potassium, or cesium. The general formula for an alkali metal fullerenide can be represented as M_x C_n, where M is the alkali metal, x is the number of alkali metal atoms (and thus electrons added), and C_n represents the fullerene cage, with n typically being 60 (for C60) or 70 (for C70).

The addition of electrons significantly alters the electronic properties of the fullerene. Pristine fullerenes are typically semiconductors or insulators, but when doped with alkali metals to form fullerenides, they can exhibit metallic or even superconducting behavior. The degree of charge transfer from the alkali metal to the fullerene cage is crucial in determining these properties. For instance, certain alkali metal fullerides, such as K3C60, are known superconductors at relatively high temperatures compared to other inorganic superconductors. The precise arrangement of the fullerene anions and the intervening alkali metal cations within the crystal lattice plays a vital role in these fascinating electronic phenomena. Research continues to explore the diverse properties and potential applications of various fullerenide compounds.