Different packing motifs of isomeric ()-'-(halo-phenyl-methyl-idene)--methyl-2-(thio-phen-2-yl)acetohydrazides controlled by C-H⋯O inter-actions.

The crystal structures of three isomeric ()-'-(chloro-phenyl-methyl-idene)--methyl-2-(thio-phen-2-yl)acetohydrazides (CHClNOS) are described, with the Cl atom in (I), (III) and (IV) positions in the benzene ring. The -bromo derivative (II) (CHBrNOS), 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 = 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 (14) loops. In the crystal of (III), [010] (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 (9) [301] chains. Hirshfeld fingerprint percentage contact contributions are similar for the four title compounds.