High-yielding syntheses, crystal structures and Hirshfeld surface analysis of bis-1,1'-(2- nitropropenes) extended with benzene-1,4-diyl and biphenyl-4,4'-diyl spacers

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-•-hole interactions of nitro groups to the crystal packing of extended polyaromatic molecules. For the former structure, these bonds complement slipped •-• 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-•-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•••• bonds. Different types of C-H•••O, C-H••••, •-•, NO2-•, NO2•••NO2, tetrel CH3•••O and CH3••• 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.