The current paper is aimed at the determination of barriers that govern the covalent coupling between partners of C60-based composites consisting of two fullerenes C60 (C60 dimer), C 60 and single-walled carbon nanotubes ([C60-(4,4)] carbon nanobuds), and C60 and graphene ([C60-(5,5)] and [C 60-(9,8)] graphene nanobuds). Barrier energies are determined as coupling ones Etotcpl and are expanded over two contributions that present the total energy of deformation of the composites' components Etotdef and the energy of covalent coupling Etotcov. In view of these energetic parameters and in contrast to expectations, seemingly identical reactions that are responsible for the formation of intermolecular [2 + 2] cycloadditions in the studied composites result in different final products. This peculiarity is suggested to occur as a result of the topochemical character of the covalent coupling between the two members of the studied composites, once additionally complicated by the varied donor-acceptor contribution. © 2011 The Royal Society of Chemistry.