[:pb]Authors: Cardoso, L. N. F.; Nogueira, T. C. M.; Wardell, J. L.; De Souza, M. V. N.; Harrison, W. T. A.
Source: Acta Crystallographica Section e, Crystallographic Communications, v. 74, p. 313-318, 2018
Publisher: Science Direct
The crystal structures of three isomeric (E)-N′-(chlorophenylmethylidene)-N-methyl-2-(thiophen-2-yl)acetohydrazides (C14H13ClN2OS) are described, with the Cl atom in ortho (I), meta (III) and para (IV) positions in the benzene ring. The ortho-bromo derivative (II) (C14H13BrN2OS), 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—Ct (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—HO interactions, which generate R22(14) loops. In the crystal of (III),  C(8) chains arise, with adjacent molecules linked by pairs of C—HO hydrogen bonds. The packing for (IV) features unusually short C—HO interactions arising from an H atom attached to the benzene ring (HO = 2.18 Å), which lead to C(9)  chains. Hirshfeld fingerprint percentage contact contributions are similar for the four title compounds.
Keywords: crystal structure,carbohydrazide,methylation,weak hydrogen bonds
Document Type: Research Article
Publication date: Março de 2018[:]