3-Penta­none 2,4-dinitro­phenyl­hydrazone

Crystals of the title compound, C11H14N4O4, were obtained from a condensation reaction of 2,4-dinitro­phenyl­hydrazine and 3-penta­none. In the crystal structure, the mol­ecule, except one methyl group, displays a nearly planar structure. The imino group links to the adjacent nitro group via intra­molecular hydrogen bonding. The partially overlapped arrangement and face-to-face separation of 3.410 (9) Å between parallel benzene rings indicate the existence of π–π stacking between adjacent mol­ecules. The crystal structure also contains weak inter­molecular C—H⋯O hydrogen bonding

2-Methyl­benzaldehyde 2-methyl­benzyl­idenehydrazone

The mol­ecule of the title compound, C16H16N2, is centrosymmetric and the dihedral angle between the benzene ring and the dimethyl­hydrazine mean plane is 16.11 (15)°

3-Ethyl-4-[(E)-2-methyl­benzyl­idene­amino]-1H-1,2,4-triazole-5(4H)-thione

Crystals of the title compound, C12H14N4S, were obtained from a condensation reaction of 4-amino-3-ethyl-1H-1,2,4-triazole-5(4H)-thione and 2-methyl­benzaldehyde. In the mol­ecular structure, there is a short N=C double bond [1.255 (2) Å], and the benzene and triazole rings are located on opposite sites of this double bond. The two rings are approximately parallel to each other, the dihedral angle being 1.75 (11)°. A partially overlapped arrangement is observed between the nearly parallel triazole and benzene rings of adjacent mol­ecules; the perpendicular distance of the centroid of the triazole ring from the benzene ring is 3.482 Å, indicating the existence of π–π stacking in the crystal structure

(E)-2-Acetyl­pyrazine 4-nitro­phenyl­hydrazone

In the title compound, C12H11N5O2, the mol­ecule adopts an E configuration, with the benzene and pyrazine rings located on opposite sides of the N=C double bond. The face-to-face separations of 3.413 (14) and 3.430 (8) Å, respectively between parallel benzene rings and between pyrazine rings indicate the existence of π–π stacking between adjacent mol­ecules. The crystal structure also contains N—H⋯N and C—H⋯O hydrogen bonding