Different conformations and packing motifs in the crystal structures of four thio-phene-carbohydrazide-pyridine derivatives.

The crystal structures of four thio-phene-carbohydrazide-pyridine derivatives, '-[()-pyridin-3-yl-methyl-idene]thio-phene-2-carbohydrazide, CHNOS, (I), '-[()-pyridin-2-yl-methyl-idene]thio-phene-2-carbohydrazide, CHNOS, (II), -methyl-'-[()-pyridin-2-yl-methyl-idene]thio-phene-2-carbohydrazide, CHNOS, (III) and '-[()-pyridin-2-yl-methyl-idene]-2-(thio-phen-2-yl)ethano-hydrazide, CHNOS, (IV) are described. The dihedral angles between the thio-phene ring and the pyridine ring are 21.4 (2), 15.42 (14), 4.97 (8) and 83.52 (13)° for (I)-(IV), respectively. The thio-phene ring in (IV) is disordered over two orientations in a 0.851 (2):0.149 (2) ratio. Key features of the packing include N-H⋯N (p = pyridine) hydrogen bonds in (I), which generate (7) chains propagating in the [001] direction; N-H⋯N links also feature in (II), but in this case they lead to (6) [001] chains; in (IV), classical amide (4) N-H⋯O links result in [010] chains; in every case adjacent mol-ecules in the chains are related by 2 screw axes. There are no classical hydrogen bonds in the extended structure of (III). Various weak C-H⋯ ( = O, N, S) inter-actions occur in each structure, but no aromatic π-π stacking is evident. The Hirshfeld surfaces and fingerprint plots for (I)-(IV) are compared.