Hydrides and dimers of C58 fullerenes: structures and stabilities

Abstract

A density functional theory (DFT) study of fullerene hydrides C₅₈H_2x (2x = 2,4,…,34) is presented. We consider two relevant isomers, the most stable classical isomer C₅₈–C_3v and the energetically close non-classical isomer C₅₈–C_s, which contains a heptagonal ring. Iterative pairwise addition of hydrogen atoms to only the energetically favoured products of the previous iteration yields a set of low energy structures for each composition. From these, low energy pathways are extracted. Analysis of the C–H binding energies along the reaction pathways is performed to identify particularly stable hydride compositions. These are 2x = 6,18,28,34 for C₅₈–C_s and 2x = 10,26,30 for C₅₈–C_3v. We therefore suggest that these hydrides are preferably formed in hydrogenation experiments and that it should be possible to distinguish between the two C₅₈ isomers. We further investigate the dimer formation based on low energy C₅₈H₂ addition patterns. All dimers show binding energies of more than 1 eV whereby dispersion interactions play a significant role. Both C₅₈ isomers can also undergo further aggregation. This leads us to the conclusion that in the absence of other reactant molecules C₅₈ will form intercage bonds and cannot be isolated in molecular form, which is in accordance with experimental results.