Halogen Bonds with Benzene: an Assessment of DFT Functionals

The performance of an extensive set of DFT functionals has been tested against CCSD(T) and MP2 results, extrapolated to the Complete Basis Set limit, for the interaction of either DCl or DBr (D = H, HCC, F and NC) with the aromatic system of benzene. It was found that double hybrid functionals explicitly including dispersion, i.e., B2PLYPD and mPW2PLYPD, provide the better agreement with the CCSD(T)/CBS results on both energies and equilibrium geometry, indicating the importance of dispersive contributions in determining this interaction. Among the less expensive functionals, the better performance is provided by the wB97X and M062X functionals, while the wB97XD and B97D functionals are shown to work very well for bromine complexes but not so well for chlorine complexes.