Four (E,Z,E)-1-(4-alkoxyphenyl)-6-(4-nitrophenyl)hexa-1,3,5-trienes.

The crystal structures of the four E,Z,E isomers of 1-(4-alkoxyphenyl)-6-(4-nitrophenyl)hexa-1,3,5-triene, namely (E,Z,E)-1-(4-methoxyphenyl)-6-(4-nitrophenyl)hexa-1,3,5-triene, C(19)H(17)NO(3), (E,Z,E)-1-(4-ethoxyphenyl)-6-(4-nitrophenyl)hexa-1,3,5-triene, C(20)H(19)NO(3), (E,Z,E)-1-(4-nitrophenyl)-6-(4-n-propoxyphenyl)hexa-1,3,5-triene, C(21)H(21)NO(3), and (E,Z,E)-1-(4-n-butoxyphenyl)-6-(4-nitrophenyl)hexa-1,3,5-triene, C(22)H(23)NO(3), have been determined. Intermolecular N...O dipole interactions between the nitro groups are observed for the methoxy derivative, while for the ethoxy derivative, two adjacent molecules are linked at both ends through N...O dipole-dipole interactions between the N atom of the nitro group and the O atom of the ethoxy group to form a supramolecular ring-like structure. In the crystal structures of the n-propoxy and n-butoxy derivatives, the shortest intermolecular distances are those between the two O atoms of the alkoxy groups. Thus, the nearest two molecules form an S-shaped supramolecular dimer in these crystal structures.