LOCAL SOFTNESS AND HARDNESS AS REACTIVITY INDEXES IN THE FULLERENES C-24-C-76

The condensed local softness, s(k)(+) or condensed fukui function, f(k )(+), approximated by Mulliken atomic charge differences, are used as a descriptor of the regioselectivity for the fullerenes (from C-24 to C-76) towards a nucleophilic attack. In general the results, which are in agreement with experimental data, can be interpreted in terms of a pyramidalization angle effect, soft-hard alternations and softness de localization. The local hardness on the most reactive carbon atom in e ach fullerene turns out to be a valuable descriptor of the intermolecu lar reactivity sequence. The maximal hardness principle is used to dis cuss the stability for the larger fullerenes (C-50, C-60, C-70 and C-7 6) The calculated hardness, approximately calculated as the LUMO-HOMO energy difference, confirms the fact that C-60 and C-70 are the most s table fullerenes.