The valence of small fullerenes

The production and isolation of small fullerenes and of their stable compounds and the knowledge of their chemistry should pave the way to the syntesis of novel carbon-based cluster-assembled materials like carbon clathrates, hollow diamonds and diamond-like thin films. In this quest, the knowledge of the valence of the small fullerenes is essential. We report here that the small fullerenes Cn (20 ≤ n ≤ 32), aside from the well known values associated with the local one electron picture of dangling bonds, display hidden valences connected with the free electron picture of the shell structure of π-electrons.