Evaluation of viability of halogen⋯O₂N interactions: Insight from crystal packing in a series of isomeric halo and nitro substituted triaryl compounds with modular positioning of halogen and NO₂ groups

Abstract

A series of isomeric triaryl compounds with a modular positioning of the halogen and NO₂ groups have been synthesized by the azide–alkyne “click reaction” and have been characterized by single crystal X-ray structure analysis. This isomeric series has provided an opportunity for understanding the efficiency of the bifurcated halogen⋯NO₂ synthon in the organization of the molecules in the crystalline lattice. The changes in molecular conformation, crystal packing and supramolecular aggregation due to the change in the relative positioning of the complementary groups, halogen atom and the NO₂ group on ring A and ring C respectively, have been discussed. All the isomers synthesized are crystalline and establish the triazole as a reliable linker for crystal engineering oriented molecular synthesis. The 2-NO₂ derivatives display in general, a helical architecture and 3-NO₂ derivatives exhibit a centrosymmetric dimeric assembly via the complementary C–H⋯O interactions leading to either a helical or a 2-dimensional sheet pattern. The molecular organization in 4-NO₂ derivatives revealed in general a 2D sheet pattern.