Regioselectivity in multiple cycloadditions to fullerene C60: vibronic coupling density analysis

We theoretically investigate multiple cycloadditions of butadienes to fullerene C60 with the concept of vibronic coupling density (VCD) as a reactivity index. Recently, we have clarified that C60 bears ethylene moieties at its reactive sites as functional groups, on the basis of VCD. In this study, we calculate the VCDs of C60 adducts with n butadienes (n=1, …, 5) and show that the ethylene moieties are conserved with almost the same distributions as those in C60. The VCD analysis predicts that the hexakisadduct with a six-fold axis is finally obtained, which is consistent with experimental observations.