Buckycatcher polymer versus fullerene-buckycatcher complex: Which is stronger?

Abstract

The C60H28 buckycatcher (BC) is an excellent host for fullerenes. This receptor features two corannulene pincers which trap C60/C70 via π stacking interactions. Although, the formation of C60@C60H28 complexes is readily observed, the dimerization of C60H28 is not a competitive process, even at high concentrations. By means of first principle calculations, we have studied the thermodynamics of the polymerization of BCs and the formation of fullerene complexes. The results obtained with the M06-2X, B97-D, B3LYP-D3BJ, PBE-D2, and PBE-D3 functionals indicated that the interaction energy of (C60H28)2 is larger than the one computed for C60@C60H28, by 8-10 kcal/mol. Because of the greater number of atoms, and due to the presence of more hydrogens, the inclusion of free energy corrections lowers the energetic separation between (C60H28)2 and C60@C60H28, even though the dimer maintains its position as being slightly more bound than that of the C60@C60H28. Our calculations indicated that up to the C60H28 trimer could be formed with a free energy change larger than that corresponding to the dimerization and fullerene complexation processes. Finally, we found that the inversion of the corannulene pincers attached to the cyclooctatetraene core is 2-3 kcal/mol lower than that corresponding to free corannulene. We expect that this work can motivate new investigations that may lead to the observation of C60H28 polymers.