Direct Observation of the Transition from Static to Dynamic Jahn-Teller Effects in the [Cs(THF)4]C_(60) Fulleride

摘要

Fullerenes feature a number of unique chemical and physical phenomena. Among these the commonly high electron affinity allows for an easy uptake of excess electrons. In most cases, the resulting anions are open-shell species, which give rise to a variety of fascinating electronic effects in fulleride-based extended solids, such as superconductivity or ferromagnetism. The mechanisms behind these collective properties are not yet fully clarified, however, they have been tentatively associated to respective local electronic structures. For C_(60), and also for many other highly symmetric fullerene cages, the frontier orbitals arc degenerate and may get unequally occupied upon reduction. Such a scenario inevitably should result in a Jahn-Teller effect (JT). Meanwhile, a number of theoretical analyses have become available, which all agree in that the JT distortion should be fairly small, leading to orbital splittings of less than 0,1 eV. As a geometric response, most investigators have considered a global distortion of the C_(60) cage to an ellipsoidal body.