Intermolecular interactions in crystals of benzene and its mono- and dinitro derivatives: study from the energetic viewpoint

Abstract

Intermolecular interactions and their role in the crystal packing formation have been studied in benzene, mono-nitrobenzene and all isomers of dinitrobenzene crystals. In both polymorphic structures of benzene, stacking interactions are absent and weak C–H⋯π hydrogen bonds play the main role in the crystal packing formation. The insertion of nitro groups into the benzene molecule causes the formation of stronger C–H⋯O intermolecular hydrogen bonds and stacking interactions instead of weaker C–H⋯π interactions. The analysis of pairwise interaction energies revealed that the stacking interactions form the primary structural motif in the crystals of nitro-substituted benzenes with the exception of para-dinitrobenzene. The existence of stacking interactions was shown to need not only the special orientation of π-systems but also the polarization of the molecule. It was shown that C–H⋯O hydrogen bonds play the minor role in the crystals of mono- and dinitrobenzenes where these interactions link the primary basic structural motifs. The C–H⋯O hydrogen bonds were shown to be weaker than non-specific interactions in the absence of stacking in the para-dinitrobenzene crystal.