Halogen Bonding to the π‐Systems of Polycyclic Aromatics

Abstract The propensity of the π‐electron system lying above a polycyclic aromatic system to engage in a halogen bond is examined by DFT calculations. Prototype Lewis acid CF 3 I is placed above the planes of benzene, naphthalene, anthracene, phenanthrene, naphthacene, chrysene, triphenyl, pyrene, and coronene. The I atom positions itself some 3.3–3.4 Å above the polycyclic plane, and the associated interaction energy is about 4 kcal/mol. This quantity is a little smaller for benzene, but is roughly equal for the larger polycyclics. The energy only oscillates a little as the Lewis acid slides across the face of the polycyclic, preferring regions of higher π‐electron density over minima of the electrostatic potential. The binding is dominated by dispersion which contributes half of the total interaction energy.

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