Different packing motifs of isomeric (E)-N′-(halo­phenyl­methyl­idene)-N-methyl-2-(thio­phen-2-yl)acetohydrazides controlled by C—H⋯O inter­actions

The crystal structures of three isomeric (E)-N′-(chloro­phenyl­methyl­idene)-N-methyl-2-(thio­phen-2-yl)acetohydrazides (C(14)H(13)ClN(2)OS) are described, with the Cl atom in ortho (I), meta (III) and para (IV) positions in the benzene ring. The ortho-bromo derivative (II) (C(14)H(13)BrN(2)OS), which is isostructural with its chloro congener (I), is also reported. Mol­ecules (I)–(III) have similar conformations, which approximate to l-shapes, as indicated by their N—C—C—C(t) (t = thio­phene) torsion angles of −90.1 (3), −91.44 (18) and −90.7 (9)°, respectively. The conformation of (IV) is different, with an equivalent torsion angle of −170.75 (11)° corresponding to a more extended shape for the mol­ecule. The thio­phene ring in each structure features ‘flip’ rotational disorder. The packing for (I) and (II) features inversion dimers, linked by pairs of C—H⋯O inter­actions, which generate R (2) (2)(14) loops. In the crystal of (III), [010] C(8) chains arise, with adjacent mol­ecules linked by pairs of C—H⋯O hydrogen bonds. The packing for (IV) features unusually short C—H⋯O inter­actions arising from an H atom attached to the benzene ring (H⋯O = 2.18 Å), which lead to C(9) [301] chains. Hirshfeld fingerprint percentage contact contributions are similar for the four title compounds.