Interplay between Halogen Bonding and Lone Pair-π Interactions: A Computational and Crystal Packing Study

The supramolecular organization of modified thiophenes resulting from N⋅⋅⋅I halogen bonding (XB) has been studied. X-ray diffraction analyses of two polymorphs of the same supramolecular complex showed an arrangement controlled by halogen-bonded pyridyl and tetrafluoroiodobenzene rings, one case with and the other without the presence of two different lone pair (lp)⋅⋅⋅π interactions, namely O⋅⋅⋅pyridyl and I⋅⋅⋅tetrafluoroiodobenzene contacts. To shed light on the interplay between these interactions, quantum mechanical calculations were performed at the ωB97X-D/6-31+G(d,p) level on both systems in the gas phase. The longer N⋅⋅⋅I distance observed in the crystal structure without lp⋅⋅⋅π interactions was also corroborated by dispersion-corrected DFT. These results represent the first case in which a synergy between lp⋅⋅⋅π interactions and XB is observed experimentally and confirmed by calculations.