Reactivity of endohedral metallofullerene la2@c80 in nucleophilic and electrophilic attacks: vibronic coupling...

The regioselectivities of La2@C80 in thermal nucleophilic and electrophilic attacks were theoretically investigated using vibronic coupling density (VCD) analysis. Nucleophilic and electrophilic cycloadditions to La2@C80 were experimentally reported to yield [6,6] and [6,5] adducts, respectively, as major products. VCD analysis provided a clear explanation for these experimental results. For nucleophilic reactions, it was found that the reactive [6,6] bonds did not have a large lowest unoccupied molecular orbital (LUMO) density and Fukui function but a large potential derivative with respect to a reaction mode. The VCD illustrates the origin of the interaction between the electronic and vibrational states. On the other hand, conventional reactivity indices such as frontier orbital density take only the electronic state into account. The result suggested that the stabilization due to vibronic couplings plays an important role in the regioselectivity of nucleophilic cycloadditions. The VCD with respect to the effective mode could provide a picture of the functional groups, which are the double bonds of ethylene moieties. VCD analysis with respect to hypothetical localized modes enabled the quantitative prediction of regioselectivities.