Simultaneous aromatic-beryllium bonds and aromatic-anion interactions: naphthalene and pyrene as models of fullerenes, carbon single-walled nanotubes, and graphene.

The possibility of forming stable BeR2 :ArH:Y(-) (R=H, F, Cl; ArH=naphthalene, pyrene; Y=Cl, Br) ternary complexes in which the beryllium compounds and anions are located on the opposite sides of an extended aromatic system is explored by means of MP2/aug-cc-pVDZ ab initio calculations. Comparison of the electron-density distribution of these ternary complexes with the corresponding BeR2 :ArH and ArH:Y(-) binary complexes reveals the existence of significant cooperativity between the two noncovalent interactions in the triads. The energetic effects of this cooperativity are quantified by evaluation of the three-body interaction energy Δ(3) E in the framework of the many-body interaction-energy (MBIE) approach. Although an essential component of the interaction energies is electrostatic and is well reflected in the changes in the molecular electrostatic potential of the aromatic system on complexation, strong polarization effects, in particular for the BeR2 :ArH interactions, also play a significant role. The charge transfers associated with these polarization effects are responsible for significant distortion of both the BeR2 and the aromatic moieties. The former are systematically bent in all the complexes, and the latter are curved to a degree that depends on the nature of the R substituents of the BeR2 subunit.