π‐π Stacking of curved carbon networks: The corannulene dimer

Dimers of corannulene, a curved, saucer shaped molecule, were studied by theoretical calculations using second order Møller‐Plesset perturbation theory and a large polarized triple zeta basis set. Three dimer motifs were investigated: the “native” dimer is the concave‐convex stacking of two monomers with the geometries of both monomers conserved; the “planar” motif with both monomers forced to be planar; and the “C 60 ‐like” dimer where the outer monomer has the native geometry while the inner one has the curvature of buckminsterfullerene C 60 . Both staggered and eclipsed conformations of the dimers were investigated. Our calculations show that the binding energy of the native concave‐convex corannulene dimer is quite substantial (17.2 kcal/mole at the “best” SCS‐MP2/cc‐pvtz level of theory) with an equilibrium distance of about 3.64 Å. Surprisingly, there are only minor differences in both binding energies and equilibrium distances between the three different dimer motifs. This suggests that the curvature of the conjugated carbon networks does not disable their ability to form π‐π stacked assemblies similar to the planar systems. However, in contrast to the planar systems, at least part of the binding energies in the stacked curved systems can be attributed to attractive electrostatic dipole‐dipole contributions since buckybowls exhibit significant dipole moments. For the “planar” dimer, a staggered arrangement of the two monomers is preferred, while eclipsed conformations are the most stable for all curved dimers. For all systems, the basis set superposition errors are large (ca. 7 kcal/mol) at the equilibrium distance even with our largest basis sets. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009