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The crystal structures of three isomeric ( E )- N '-(chloro-phenyl-methyl-idene)- N -methyl-2-(thio-phen-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. Mol-ecules (I)-(III) have similar conformations, which approximate to l-shapes, as indicated by their N-C-C-C t (t = thio-phene) 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 mol-ecule. The thio-phene ring in each structure features 'flip' rotational disorder. The packing for (I) and (II) features inversion dimers, linked by pairs of C-H⋯O inter-actions, which generate R 2 2 (14) loops. In the crystal of (III), [010] C (8) chains arise, with adjacent mol-ecules linked by pairs of C-H⋯O hydrogen bonds. The packing for (IV) features unusually short C-H⋯O inter-actions 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.

The syntheses and crystal structures of ( E )- N '-(3-cyano-benzyl-idene)- N -methyl-2-(thio-phen-2-yl)acetohydrazide, C 15 H 13 N 3 OS, (I), and ( E )- N '-(4-meth-oxy-benzyl-idene)- N -methyl-2-(thio-phen-2-yl)acetohydrazide, C 15 H 16 N 2 O 2 S, (II), with different substituents in the meta and para position of the benzene ring are described. Compounds (I) and (II) both crystallize with two mol-ecules in the asymmetric unit, with generally similar conformations [r.m.s. overlay fits for (I) and (II) of 0.334 and 0.280 Å, respectively] that approximate to L-shapes. The thio-phene rings in (I) are well ordered, whereas those in (II) exhibit 'flip' rotational disorder [occupancies 0.662 (2) and 0.338 (2) for mol-ecule 1, and 0.549 (3) and 0.451 (3) for mol-ecule 2]. The packing for (I) features short C-H⋯O inter-actions arising from the C-H grouping adjacent to the cyanide group and C-H⋯N c (c = cyanide) links arising from the methine groups to generate [110] double chains. Weak C-H⋯π inter-actions inter-link the chains into a three-dimensional network. The packing for (II) features numerous C-H⋯O and C-H⋯π inter-actions arising from different donor groups to generate a three-dimensional network. Hirshfeld fingerprint plots indicate significant differences in the percentage contact surfaces for (I) and (II).