Hydrides and dimers of C58 fullerenes: structures and stabilities

A density functional theory (DFT) study of fullerene hydrides C58H2x (2x = 2,4,…,34) is presented. We consider two relevant isomers, the most stable classical isomer C58–C3v and the energetically close non-classical isomer C58–Cs, 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–Cs and 2x = 10,26,30 for C58–C3v. 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.