Fullerene and corannulene derivatives acting as insulators of Cl− and BeH2†
The capacity of corannulene and its benzo-derivatives CxH10 (x = 20–60) as prototypes of non-planar π-aromatic systems which mimic the end of carbon nanotubes to act as insulators between BeH2 and Cl− chemical entities has been explored by means of M06-2x/cc-pVDZ and M06-2x/6-311+G(d) calculations. For the sake of completeness, the set investigated includes also fullerene, C60. All these aromatic derivatives lead to stable binary complexes either with BeH2 or halogen (Cl−) anions. For BeH2, however, only the complexes in which the interaction involves the convex face of the aromatic system are stable. No significant changes are observed when the binding energies (BEs) of the BeH2 complexes are compared to those involving planar aromatic compounds, but the ones involving Cl− with the concave face of the aromatic moiety can be very large, because its curvature favors many contacts of the anion with the carbon atoms of the π-aromatic system. The formation of these binary complexes changes to a large extent the electrostatic potential on the free face of the aromatic system leading to a mutual reinforcement of both interactions, the beryllium bond and the interaction with Cl−, when the ternary complexes are formed. As a result, the BEs for the triads are larger than the sum of the BEs of the corresponding binary complexes and the distances between the aromatic subunit and BeH2 or Cl− become shorter in the triads than in the binary complexes. A MBIE analysis also indicates that the enhanced stability of ternary complexes arises mainly from the reinforcement of the beryllium bonds as well as from the three-body terms. An exploration of all the minima for BeH2:C60H10:Cl− shows that BeH2 binds preferentially to the peripheral aromatic rings than those in the more curved region.