(E)-Methyl 1,3-thiazol-2-yl ketone 2,4-dinitrophenylhydrazone

Crystals of the title compound, C11H9N5O4S, were obtained from a condensation reaction of 2,4-dinitrophenylhydrazine and methyl 1,3-thiazol-2-yl ketone. Excluding two methyl H atoms, the molecule displays a planar structure, the dihedral angle between the terminal thiazole and benzene rings being 1.82 (8)°. The imino group links with adjacent nitro and thiazole groups by intramolecular bifurcated hydrogen bonding. The centroid–centroid separation of 3.7273 (11) Å between nearly parallel benzene and thiazole rings of adjacent molecules indicates the existence of π–π stacking in the crystal structure. Weak intermolecular C—H⋯O hydrogen bonding is also observed.


Comment
As some phenylhydrazone derivatives have shown to be potentially DNA damaging and mutagenic agents (Okabe et al., 1993), a series of new phenylhydrazone derivatives have been synthesized in our laboratory (Shan et al., 2003;Shan et al., 2006). As part of the ongoing investigation, the title compound has recently been prepared and its crystal structure is reported here.
The molecular structure of the title compound is shown in Fig. 1. The molecule displays a coplanar structure, except methyl H atoms, the dihedral angle between the thiazole and benzene rings being 1.82 (8)°. The N4-C7 bond distance is significantly shorter than N3-N4 and N3-C1 bond distances (Table 1), and indicates the typical C?N double bond. The phenylhydrazone and thiazole are located on the opposite sides of the C?N double bond, the molecule has an E-configuration, similar to that found in a related compound, (E)-2-furlyl methylketone 2,4-dinitrophenylhydrazone (Shan et al., 2008). The imino group links with adjacent nitro and thiazole groups by intra-molecular bifurcated hydrogen bonding ( Fig. 1 and Table   2).
A partially overlapped arrangement between nearly parallel benzene ring and thiazole ring of the adjacent molecule is illustrated in Fig. 2. The dihedral angle and centroid-to-centroid separation are 1.82 (8)° and 3.7273 (11) Å, these suggest the existence of π-π stacking between adjacent molecules in the crystal. The crystal structure also contains intermolecular weak C-H···O hydrogen bonding (Table 2).
Experimental 2,4-Dinitrophenylhydrazine (0.4 g, 2 mmol) was dissolved in ethanol (10 ml), and H 2 SO 4 solution (98%, 0.5 ml) was slowly added to the ethanol solution with stirring. The solution was heated at 333 K for several min until the solution cleared.
2-Thiazolyl methyl ketone (0.25 g, 2 mmol) was added to the above solution with continuous stirring, and the mixture was refluxed for 30 min. When the solution had cooled to room temperature yellow powder crystals appeared. The powder crystals were separated and washed with water three times. Recrystallization from an absolute ethanol yielded well shaped single crystals.

Refinement
Methyl H atoms were placed in calculated positions with C-H = 0.96 Å and the torsion angle was refined to fit the electron density, U iso (H) = 1.5U eq (C). Other H atoms were placed in calculated positions with C-H = 0.93 and N-H = 0.86 Å, and refined in riding mode with U iso (H) = 1.2U eq (C,N). Fig. 1. The molecular structure of the title compound with 30% probability displacement ellipsoids for non-H atoms, dashed lines indicate hydrogen bonding. (E)-Methyl 1,3-thiazol-2-yl ketone 2,4-dinitrophenylhydrazone as those based on F, and R-factors based on ALL data will be even larger.