The nature of interactions of benzene with CF3I and CF3CH2I

Abstract

In situ grown crystals of CF₃I and CF₃CH₂I are dominated by I⋯I and F⋯F interactions. Their co-crystals with benzene, (CF₃I)₂·C₆H₆ and CF₃CH₂I·C₆H₆, contain two completely different sets of intermolecular interactions. (CF₃I)₂·C₆H₆ shows a unique halogen-bond type: above-the-bond C–I⋯π_C6H6 interactions. CF₃CH₂I·C₆H₆ shows above-the-centre C–H⋯π_C6H6 interactions. These interactions are electrostatically dominated type II halogen bonds between single halogenoalkane molecules and weaker dispersion dominated interactions between the co-crystal components. The observed preferences for benzene for the two binding partners match with calculated molecular electrostatic potentials.