Abstract
Crystal structures of two 2-nitropropene derivatives, namely 1,4-bis((E)-2-nitroprop-1-enyl)benzene and 4,4′-bis((E)-2-nitroprop-1-enyl)biphenyl, support relevance of lone pair-π-hole interactions of nitro groups to the crystal packing of extended polyaromatic molecules. For the former structure, these bonds complement slipped π-π interactions of the benzene rings within a basic supramolecular motif representing infinite stacks. In the biphenyl derivative, only one out of two nitro groups afford NO2⋅⋅⋅NO2 bonds (N⋅⋅⋅O = 3.191(2) Å) as a local pattern. The decreased significance of lone pair-π-hole interactions is in line with growing contribution of weak dispersion forces, which favor close alignment of the molecules and larger interaction ares to generate multiple C-H⋅⋅⋅π bonds. Different types of C-H⋅⋅⋅O, C-H⋅⋅⋅π, π-π, NO2-π, NO2⋅⋅⋅NO2, tetrel CH3⋅⋅⋅O and CH3⋅⋅⋅π bonds, which actualize in the prefesent structures were further assessed by Hirshfeld surface analysis and intermolecular interaction energies were calculated using the CE B3LYP/6 31G(d,p) energy model. In addition, the facile and high-yielding preparations by condensation of dialdehydes and nitroethane, provide a straightforward access to the present 2-nitropropenes, as valuable synthetic intermediates.