(E)‐4‐[2‐(3,4,5‐Trimethoxyphenyl)ethenyl]nitrobenzene and its `bridge‐flipped' analogues

The solid‐state structures of three push–pull acceptor‐π‐donor (A‐π‐D) systems differing only in the nature of the π‐spacer have been determined. (E)‐1‐Nitro‐4‐2‐(3,4,5‐trimethoxyphenyl)ethenyl]benzene, C₁₇H₁₇NO₅, (I), and its `bridge‐flipped' imine analogues, (E)‐3,4,5‐trimethoxy‐N‐(4‐nitrobenzylidene)aniline, C₁₆H₁₆N₂O₅, (II), and (E)‐4‐nitro‐N‐(3,4,5‐trimethoxybenzylidene)aniline, C₁₆H₁₆N₂O₅, (III), display different kinds of supramolecular networks, viz. corrugated planes, a herringbone pattern and a layered structure, respectively, all with zero overall dipole moments. Only (III) crystallizes in a noncentrosymmetric space group (P2₁2₁2₁) and is, therefore, a potential material for second‐harmonic generation (SHG).