Molecules of 1-(6-amino-1,3-benzodioxol-5-yl)-3-(4-methylphenyl)prop-2-en-1-one, C 17 H 15 NO 3 , (I), 1-(6-amino-1,3-benzodioxol-5-yl)-3-(4-methoxyphenyl)prop-2-en-1-one, C 17 H 15 NO 4 , (II), and 1-(6-amino-1,3-benzodioxol-5-yl)-3-[4-(trifluoromethyl)phenyl]prop-2-en-1-one, C 17 H 12 F 3 NO 3 , (III), all contain an intramolecular N—H...O hydrogen bond and all exhibit polarized molecular–electronic structures. The molecules of (I) are linked into simple sheets, generated by translation, by means of one N—H...O and one C—H...π(arene) hydrogen bond. Compound (II) crystallizes as two concomitant polymorphs, viz . (II a ), with Z ′ = 1 in P 2 1 / c , and (II b ), with Z ′ = 2 in P \overline 1. In (II a ), intra- and intermolecular N—H...O hydrogen bonds generate a helical chain of rings, and these chains are linked into sheets by simple helical chains built from a C—H...π(arene) hydrogen bond, while in (II b ), the molecules are linked into simple chains by a C—H...O hydrogen bond. In (III), where Z ′ = 2, each type of molecule forms a simple N—H...O hydrogen-bonded chain generated by translation and the two types of chain are linked by a single π–π stacking interaction.