Computational studies of the intermolecular interactions in dimers of the bowl-shaped sumanene molecule

Sumanene, C 21 H 12 , the second smallest “buckybowl,” is a bowl-shaped fragment of buckminsterfullerene, C 60 . It can be described as a slice of buckminsterfullerene with 21 carbon atoms with all vacant valences terminated by hydrogens. A computational study of dimers of the sumanene molecule has been carried out. The concave–convex surface arrangement is the most favorable arrangement, and the binding energy and the equilibrium distance for the most stable conformation of the sumanene dimer are predicted to be 19.3 kcal/mol and 3.7 Å, respectively. The most stable geometry was the staggered stacked concave–convex motif, where one monomer was rotated by 60° from the eclipsed conformation. The binding energy of the eclipsed concave–convex dimer is predicted to be 16.7 kcal/mol with an equilibrium distance between the monomer units of 3.8 Å. At the MP2 level, the basis set superposition errors are quite large, 3–5 kcal/mol at the equilibrium distance depending on the basis set. The basis set superposition errors are smaller for dispersion-corrected density functional methods.