Structure of 2,4-dinitrophenylhydrazine

Trigger bond analysis of nitroaromatic energetic materials using wiberg bond indices

The identification of trigger bonds, bonds that break to initiate explosive decomposition, using computational methods could help direct the development of novel, "green" and efficient high energy density materials (HEDMs). Comparing bond densities in energetic materials to reference molecules using Wiberg bond indices (WBIs) provides a relative scale for bond activation (%ΔWBIs) to assign trigger bonds in a set of 63 nitroaromatic conventional energetic molecules. Intramolecular hydrogen bonding interactions enhance contributions of resonance structures that strengthen, or deactivate, the CNO₂ trigger bonds and reduce the sensitivity of nitroaniline-based HEDMs. In contrast, unidirectional hydrogen bonding in nitrophenols strengthens the bond to the hydrogen bond acceptor, but the phenol lone pairs repel and activate an adjacent nitro group. Steric effects, electron withdrawing groups and greater nitro dihedral angles also activate the CNO₂ trigger bonds. %ΔWBIs indicate that nitro groups within an energetic molecule are not all necessarily equally activated to contribute to initiation. %ΔWBIs generally correlate well with impact sensitivity, especially for HEDMs with intramolecular hydrogen bonding, and are a better measure of trigger bond strength than bond dissociation energies (BDEs). However, the method is less effective for HEDMs with significant secondary effects in the solid state. Assignment of trigger bonds using %ΔWBIs could contribute to understanding the effect of intramolecular interactions on energetic properties. © 2018 Wiley Periodicals, Inc.

Estimating the densities of benzene-derived explosives using atomic volumes

The application of average atomic volumes to predict the crystal densities of benzene-derived energetic compounds of general formula C _a H _b N _c O _d is presented, along with the reliability of this method. The densities of 119 neutral nitrobenzenes, energetic salts, and cocrystals with diverse compositions were estimated and compared with experimental data. Of the 74 nitrobenzenes for which direct comparisons could be made, the % error in the estimated density was within 0-3% for 54 compounds, 3-5% for 12 compounds, and 5-8% for the remaining 8 compounds. Among 45 energetic salts and cocrystals, the % error in the estimated density was within 0-3% for 25 compounds, 3-5% for 13 compounds, and 5-7.4% for 7 compounds. The absolute error surpassed 0.05 g/cm³ for 27 of the 119 compounds (22%). The largest errors occurred for compounds containing fused rings and for compounds with three -NH₂ or -OH groups. Overall, the present approach for estimating the densities of benzene-derived explosives with different functional groups was found to be reliable. Graphical abstract Application and reliability of average atom volume in the crystal density prediction of energetic compounds containing benzene ring.

Crystal structure and DFT study of (E)-2,6-di-tert-butyl-4-{[2-(pyridin-2-yl)hydrazin-1-yl-idene)meth-yl}phenol

The title compound, C20H27N3O, was synthesized by condensation reaction of 3,5-di-tert-butyl-4-hy-droxy-benzaldehyde and 2-hydrazinyl-pyridine, and crystallizes in the centrosymmetric monoclinic space group C2/c. The conformation about the C=N bond is E. The dihedral angle between the rings is 18.1 (3)°. An inter-molecular N-H⋯N hydrogen bond generates an R22(8) ring motif. In the crystal, N-H⋯N hydrogen bonds connect pairs of mol-ecules, forming dimers. Density functional theory (DFT) optimized structures at the B3LYP/6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state.

Crystal structure of (E)-1-[1-(3-chloro-4-fluoro-phenyl)ethylidene]-2-(2,4-dinitrophenyl)hydrazine, C28H20Cl2F2N8O8

C28H20Cl2F2N8O8, triclinic, P1̅ (no. 2), a = 9.045(3) Å, b = 10.907(4) Å, c = 15.351(5) Å, α = 93.416(7)°, β = 95.771(7)°, γ = 95.915(6)°, V = 1495.0(9) Å3, Z = 4, R gt(F) = 0.0655, wR ref(F 2) = 0.1940, T = 293 K.

Crystal structure of (E)-2,6-di-tert-butyl-4-{[2-(2,4-di-nitro-phen-yl)hydrazinylidene]meth-yl}phenol

The essential part (including all the non-hydrogen atoms except two methyl carbons) of the mol-ecule of the title compound, C21H26N4O5, lies on a mirror plane, which bis-ects the t-butyl groups. The conformation of the C=N bond of this Schiff base compound is E, and there is an intra-molecular N-H⋯O hydrogen bond present, forming an S(6) ring motif. In the crystal, mol-ecules are linked via O-H⋯O hydrogen bonds, forming zigzag chains propagating along the a-axis direction. There are no other significant inter-molecular contacts present.

N'-(2,4-Di-nitro-phen-yl)acetohydrazide monohydrate

In the crystal structure of the title compound, C8H8N4O5·H2O, the organic and lattice water mol-ecules are linked together via N-H⋯O and O-H⋯O hydrogen bonds. A C-H⋯O inter-action is also observed between the organic mol-ecules. These hydrogen bonds and inter-actions lead to the formation of a three-dimensional network. An intra-molecular N-H⋯O hydrogen bond also occurs. The dihedral angle between the acetyl group and the almost planar hydrazide moiety [maximum deviation from the least-squares plane is 0.209 (2) Å for one of the nitro O atoms] is 88.5 (3)°.

1-[(E)-Anthracen-9-yl-methyl-idene]-2-(2,4-di-nitro-phen-yl)hydrazine

In the title Schiff base, C21H14N4O4, the dihedral angle between the two nitro groups and the central benzene ring are 83.6 (5) and 2.6 (6)°. The anthracene ring system and the benzene ring make a dihedral angle of 0.7 (2)°. Intra-molecular N-H⋯O and C-H⋯N hydrogen bonds occur. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules, forming chains along the b-axis direction.

(E)-N′-(4-Chlorobenzylidene)-, (E)-N′-(4-bromobenzylidene)- and (E)-N′-[4-(diethylamino)benzylidene]- derivatives of 4-hydroxybenzohydrazide

The 4-chloro- [C14H11ClN2O2, (I)], 4-bromo- [C14H10BrN2O2, (II)] and 4-diethylamino- [C18H21N3O2, (III)] derivatives of benzylidene-4-hydroxybenzohydrazide, all crystallize in the same space group (P21/c), (I) and (II) also being isomorphous. In all three compounds, the conformation about the C=N bond isE. The molecules of (I) and (II) are relatively planar, with dihedral angles between the two benzene rings of 5.75 (12) and 9.81 (17)°, respectively. In (III), however, the same angle is 77.27 (9)°. In the crystal structures of (I) and (II), two-dimensional slab-like networks extending in theaandcdirections are formedviaN—H...O and O—H...O hydrogen bonds. The molecules stack head-to-tailviaπ–π interactions involving the aromatic rings [centroid–centroid distance = 3.7622 (14) Å in (I) and 3.8021 (19) Å in (II)]. In (III), undulating two-dimensional networks extending in thebandcdirections are formedviaN—H...O and O—H...O hydrogen bonds. The molecules stack head-to-headviaπ–π interactions involving inversion-related benzene rings [centroid–centroid distances = 3.6977 (12) and 3.8368 (11) Å].

Synthesis, molecular structure and spectral analysis of ethyl 4-[(3,5-dinitrobenzoyl)-hydrazonomethyl]-3,5-dimethyl-1H-pyrrole-2-carboxylate: a combined experimental and quantum chemical approach

A new hydrazone, ethyl 4-[(3,5-dinitrobenzoyl)-hydrazonomethyl]-3,5-dimethyl-1H-pyrrole-2-carboxylate (PDNBAH) has been synthesized and characterized by FT-IR, (1)H NMR, UV-visible spectroscopy. All the quantum chemical calculations have been performed by density functional theory (DFT), using B3LYP functional and 6-31G(d,p) as basis set. The calculated and experimental wavenumber analyses confirm the existence of dimer of PDNBAH. The calculated binding energies of dimer using DFT and Bader's atoms in molecules (AIM) theory are -14.32 and -15.41 kcal/mol respectively. The intermolecular hydrogen bond energy of dimer due to the involvement of intermolecular hetero-nuclear double hydrogen bonds (N-H···O=C) through pyrrolic N-H and C=O of ester is also calculated to be equal to -12.29 kcal/mol using AIM calculation. The strength and the nature of hydrogen bonding and weak interactions in dimer have been analyzed by AIM theory in detail. The presence of resonance assisted hydrogen bonds (RAHB) has been confirmed by calculated ellipticity parameters using AIM calculation. The calculated thermodynamic parameters show that the reaction is non spontaneous at room temperature. The local reactivity descriptors show that C(13) is most reactive site for nucleophilic attack.

Benzyl (E)-3-(2-bromo-5-meth-oxy-benzyl-idene)dithio-carbazate

The title compound, C(16)H(15)BrN(2)OS(2), was obtained from the condensation reaction of benzyl dithio-carbazate and 2-bromo-5-meth-oxy-lbenzaldehyde. In the mol-ecule, the bromo-meth-oxy-phenyl ring and dithio-carbazate fragment are located on the opposite sides of the C=N double bond, showing the E conformation. The dithio-carbazate fragment is approximately planar (r.m.s deviation 0.0187 Å); its mean plane is oriented with respect to the bromo-meth-oxy-phenyl and phenyl rings at 7.60 (12) and 60.08 (9)°, respectively. In the crystal, inversion dimers linked by pairs of N-H⋯S hydrogen bonds occur. A short Br⋯Br contact of 3.5526 (12) Å is observed in the crystal structure.

Benzyl (E)-3-(4-meth-oxy-benzyl-idene)dithio-carbazate

The title compound, C₁₆H₁₆N₂OS₂, was obtained from a condensation reaction of benzyl dithio­carbazate and 4-meth­oxy­benzaldehyde. In the mol­ecule, the meth­oxy­phenyl ring and dithio­carbazate fragment are located on opposite sides of the C=N double bond, showing an E configuration. The dithio­carbazate fragment is approximately planar (r.m.s. deviation = 0.0052 Å); its mean plane is oriented at dihedral angles of 8.19 (15) and 85.70 (13)°, respectively, to the meth­oxy­phenyl and phenyl rings. Inter­molecular N—H⋯S hydrogen bonds and weak C—H⋯π inter­actions are observed in the crystal structure.

Benzyl (E)-3-(2-methyl-benzyl-idene)dithio-carbazate

The title compound, C₁₆H₁₆N₂S₂, was obtained from the condensation reaction of benzyl dithio­carbazate and 2-methyl­benzaldehyde. The asymmetric unit contains two independent mol­ecules. In both mol­ecules, the methyl­phenyl ring and the dithio­carbazate fragment are located on opposite sides of the C=N bond, showing an E conformation. In each mol­ecule, the dithio­carbazate fragment is approximately planar, the r.m.s deviations being 0.018 and 0.025 Å. The mean plane of dithio­carbazate group is oriented at dihedral angles of 7.9 (3) and 68.24 (12)°, respectively, to the methyl­phenyl and phenyl rings in one mol­ecule, while the corresponding angles in the other mol­ecule are 10.9 (3) and 69.76 (16)°. Inter­molecular N—H⋯S hydrogen bonding occurs in the crystal structure to generate inversion dimers for both molecules.

(E)-N'-[1-(Thio-phen-2-yl)ethyl-idene]benzohydrazide

The title compound, C₁₃H₁₂N₂OS, was obtained from the condensation reaction of 2-acetyl­thio­phene and benzohydrazide. In the mol­ecule, the formohydrazide fragment is approximately planar (r.m.s deviation = 0.0146 Å) and the mean plane is oriented at dihedral angles of 24.47 (11) and 28.86 (13)°, respectively, to the phenyl and thio­phene rings. The thio­phene and phenyl rings make a dihedral angle of 53.21 (8)°. The benzamide fragment and thio­phene ring are located on the opposite sides of the C=N bond, showing an E conformation. Classical inter­molecular N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions are present in the crystal structure: three such bonds occur to the same O-atom acceptor.

(E)-1-(2,4-Dinitrophenyl)-2-(2-fluorobenzylidene)hydrazine

In the title compound, C₁₃H₉FN₄O₄, the dihedral angle between the mean planes of the two benzene rings of the nearly planar mol­ecule is 6.6 (9)°. The dihedral angles between the mean planes of the benzene ring and its two attached nitro groups are 6.7 (7) and 7.2 (9)°. Crystal packing is stabilized by N—H⋯O hydrogen bonds, weak C—H⋯O and C—H⋯F inter­molecular inter­actions and centroid–centroid π-ring stacking inter­actions.

(E)-4-{[2-(2-Furylcarbonyl)hydrazinylidene]methyl}-2-methoxyphenyl acetate

The mol­ecule of the title Schiff base compound, C₁₅H₁₄N₂O₅, was obtained from a condensation reaction of 4-acet­oxy-3-meth­oxy­benzaldehyde and 2-furyl­carbonyl­hydrazide. In the mol­ecule, the furyl ring makes a dihedral angle of 14.63 (10)° with the benzene ring. In the crystal, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into chains along the b axis. Futhermore, weak C—H⋯O inter­actions connect the chains, forming corrugated layers parallel to (001). The dihedral angle between the rings is 14.63 (10)°.

2-Chloro-N'-(2-hy-droxy-3,5-diiodo-benzyl-idene)benzohydrazide

In the title compound, C(14)H(9)ClI(2)N(2)O(2), the dihedral angle between the benzene rings is 65.9 (2)° and an intra-molecular O-H⋯N hydrogen bond generates an S(6) ring. The mol-ecule has an E conformation about the C=N bond. In the crystal, mol-ecules are linked into C(4) chains propagating in [001] by N-H⋯O hydrogen bonds.

5-Diethyl-amino-2-{[2-(2,4-dinitro-phen-yl)hydrazin-1-yl-idene]meth-yl}phenol

In the title compound, C₁₇H₁₉N₅O₅, obtained from the condensation reaction of 4-diethyl­amino-2-hy­droxy­benzalde­hyde and 2,4-dinitro­phenyl­hydrazine, the two benzene rings are twisted by a dihedral angle of 1.75 (12)°. The nitro groups are slightly twisted with the respect to the benzene ring to which they are attached, making dihedral angles of 8.20 (15) and 5.78 (15)°. An intra­molecular O—H⋯N hydrogen bond occurs. In the crystal, mol­ecules are linked by pairs of inter­molecular N—H⋯O hydrogen bonds, forming dimers through R₂²(12) rings. These dimers are further linked by C—H⋯O and C—H⋯π and weak slipped π–π inter­actions [centroid–centroid distance = 3.743 (2)Å]. One of the ethyl groups is disordered over two positions, with occupancy factors in the ratio 0.72:0.28.

Bis[4-hydroxy-3,5-dimethoxybenzaldehyde (2,4-dinitrophenyl)hydrazone]N,N-dimethylformamide disolvate monohydrate

In the title compound, 2C₁₅H₁₄N₄O₇·2C₃H₇NO·H₂O, the hydrazone mol­ecules are roughly planar, with the two benzene rings twisted slightly relative to each other by dihedral angle of 6.04 (11) and 7.75 (11)° in the two mol­ecules. The water mol­ecule is linked to the Schiff base mol­ecule by an O—H⋯O hydrogen bond. Intra­molecular N—H⋯O hydrogen bonds occur. In the crystal, mol­ecules are linked by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds.

Methyl 2-methoxy-4-{[2-(4-nitrophenyl)hydrazinylidene]methyl}benzoate

The mol­ecule of the title Schiff base compound, C₁₆H₁₅N₃O₅, obtained from a condensation reaction of 4-acet­oxy-3-meth­oxy­benzaldehyde and 4-nitro­phenyl­hydrazine, adopts an E geometry with respect to the C=N double bond. The mol­ecule is roughly planar, with the two benzene rings twisted slightly with respect to each other by a dihedral angle of 6.90 (9)°. In the crystal, inter­molecular N—H⋯O hydrogen bonds link centrosymmetrically related pairs of mol­ecules, forming dimers of R₂²(22) graph-set motif. The dimers are further connected through slipped π–π inter­actions between symmetry-related benzene rings [centroid–centroid distance of 3.646 (1) Å, offset angle of 15.4°].

(E)-N'-(3,4-Dihydroxy-benzyl-idene)-4-nitro-benzohydrazide

In the title Schiff base compound, C₁₄H₁₁N₃O₅, the dihedral angle between the two benzene rings is 1.6 (1)°. The mol­ecule displays an E configuration about the C=N bond. An intra­molecular O—H⋯O hydrogen bond is observed. In the crystal, mol­ecules are linked into layers parallel to (101) by O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. One of the hydroxyl groups is disordered over two positions, with occupancies of 0.643 (5) and 0.357 (5).

N'-[(E)-3-Indol-3-ylmethyl-ene]isonicotino-hydrazide monohydrate

Crystals of the title compound, C₁₅H₁₂N₄O·H₂O, were obtained from a condensation reaction of isonicotinylhydrazine and 3-indolylformaldehyde. The mol­ecule assumes an E configuration, with the isonicotinoylhydrazine and indole units located on the opposite sites of the C=N double bond. In the mol­ecular structure the pyridine ring is twisted with respect to the indole ring system, forming a dihedral angle of 44.72 (7)°. Extensive classical N—H⋯N, N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonding and weak C—H⋯O inter­actions are present in the crystal structure.

(E)-2-Hydroxy-naphthalene-1-carb-al-de-hyde semicarbazone

The title compound, C(12)H(11)N(3)O(2), adopts an E or trans configuration with respect to the C=N bond. There is an intra-molecular O-H⋯N hydrogen bond involving the hydroxyl H atom and an N atom of the hydrazine group. In the crystal structure, mol-ecules are connected via N-H⋯O hydrogen bonds, forming a three-dimensional network.

N-[1-(Biphenyl-4-yl)ethyl-idene]-N'-(2,4-dinitro-phen-yl)hydrazine

The title compound, C(20)H(16)N(4)O(4), contains two crystallographically independent mol-ecules (A and B) in the asymmetric unit. Intra-molecular N-H⋯O hydrogen bonds generate S(6) ring motifs in both molecules. The dihedral angles between the nitro-substituted benzene rings and the two benzene rings in mol-ecules A and B are 14.32 (9), 17.89 (9)° and 13.04 (9) and 25.71 (9)°. The ortho and para nitro groups form dihedral angles of 6.2 (2) and 8.5 (2)° in mol-ecule A, and 5.3 (3) and 13.8 (2)° in mol-ecule B, with the benzene rings to which they are attached. The crystal structure is stabilized by inter-molecular C-H⋯O inter-actions.

N-(2,4-Dinitro-phen-yl)-N'-(1-p-tolyl-ethyl-idene)hydrazine

In the title mol-ecule, C(15)H(14)N(4)O(4), the dihedral angle between the two benzene rings is 2.21 (7)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. The mean planes of the ortho- and para-nitro groups make dihedral angles of 2.17 (17) and 2.05 (16)°, respectively, with the benzene ring to which they are attached. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds generate R(2) (2)(7), R(2) (2)(13) and R(2) (1)(10) ring motifs, linking symmetry-related mol-ecules into extended chains along the b axis. In addition, there are inter-molecular C⋯C [3.332 (2)-3.343 (2) Å] contacts which are shorter than the sum of the van der Waals radii. The crystal structure is further stabilized by inter-molecular C-H⋯π and π-π stacking inter-actions [centroid-centroid distance = 3.8090 (9) Å].

(E)-N'-(3-Fluoro-benzyl-idene)-2-hydroxy-benzohydrazide

The title compound, C(14)H(11)FN(2)O(2), adopts an E or trans configuration with respect to the C=N bond. An intra-molecular N-H⋯O hydrogen bond contributes to the relatively planarity of the mol-ecular conformation; the two benzene rings are inclined to one another by 12.5 (2)°. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into chains running parallel to the c axis.

N-Cycloheptylidene-N′-(2,4-dinitrophenyl)hydrazine

The title compound, C₁₃H₁₆N₄O₄, is a new hydrazone. An intra­molecular N—H⋯O hydrogen bond generates a six-membered ring, producing an S(6) ring motif. The nitro groups in the ortho and para positions are almost coplanar with the benzene ring to which they are bound, making dihedral angles of 0.60 (11) and 3.18 (11)°, respectively. Pairs of inter­molecular C—H⋯O hydrogen bonds link neighbouring mol­ecules into inversion dimers with R₂²(10) motifs. The crystal structure is further stabilized by inter­molecular π–π inter­actions, with a benzene centroid-to-centroid distance of 3.6601 (4) Å.

(E)-4-Bromo-N'-(2-nitro-benzyl-idene)benzohydrazide

The title compound, C(14)H(10)BrN(3)O(3), was obtained by a condensation reaction between 2-nitro-benzaldehyde and 4-bromo-benzohydrazide. The dihedral angle between the two benzene rings is 4.1 (2)°. The mol-ecule displays an E configuration about the C=N bond. In the crystal, mol-ecules are linked into a chain along [100] by inter-molecular N-H⋯O hydrogen bonds.

N′-(2-Hydroxy-3-methoxybenzylidene)-1,3-benzodioxole-5-carbohydrazide monohydrate

Single crystals of the title compound, C₁₆H₁₄N₂O₅·H₂O, were obtained from a condensation reaction of 1,3-benzodioxole-5-carbohydrazide and 3-methoxy­salicylaldehyde in a 95% ethanol solution. The asymmetric unit consists of a Schiff base mol­ecule, which assumes an E configuration with respect to the C=N bond, and a water mol­ecule of crystallization. The dihedral angle between the two substituted benzene rings is 12.7 (2)°. In the crystal structure, mol­ecules are linked through inter­molecular N—H⋯O and O—H⋯O hydrogen bonds, forming layers parallel to the bc plane.

2-Methoxy-benzaldehyde 2,4-dinitro-phenyl-hydrazone

In the title compound, C(14)H(12)N(4)O(5), an intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. The dihedral angle between the two benzene rings is 3.91 (3)°, which shows the mol-ecule is almost planar. The para-nitro group is twisted from the benzene ring to which it is attached, making a dihedral angle of 8.50 (9)°. In the crystal structure, mol-ecules are linked together by inter-molecular C-H⋯O and inter-molecular three-centred O⋯O [2.8646 (12)-2.9213 (11) Å] and O⋯N [3.0518 (11) Å] inter-actions. The crystal structure is further stabilized by inter-molecular π-π inter-actions [centroid-to-centroid distances 3.5708 (6)-3.9728 (12) Å].

N'-(4-Chloro-benzyl-idene)-2-hydroxy-benzohydrazide

The title mol-ecule, C(14)H(11)ClN(2)O(2), adopts a trans configuration with respect to the C=N double bond. An intra-molecular N-H⋯O hydrogen bond contributes to mol-ecular conformation and the two benzene rings form a dihedral angle of 17.9 (8)°. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into chains running along [10].

Intermolecular interactions in 2,4-dinitrophenylhydrazine hydrochloride hydrate: X-ray structural and quantum mechanical study

2,4-dinitrophenylhydrazine hydrochloride hydrate (I) was determined by X-ray crystallography, and the intermolecular interaction energies were calculated in terms of Natural Bond Orbital analysis. The asymmetric unit of (I) consists of a dinitrophenylhydrazinium cation, a chloride anion and a water molecule. The interatomic distances and angles in (I) show no unusual values. In the structure there are intermolecular N—H⊎⊎⊎O, N—H⊎⊎⊎Cl, O—H⊎⊎⊎Cl, C—H⊎⊎⊎O hydrogen bonds with bonding energy ranging form 16.03 to 0.76 kcal mol−1. These hydrogen bonds create the following N1 motifs: 6D, S(5), S(6), C(6), C(9). N1D motifs become infinite at the third level and are 2C 32(6), C 32(7).

Thio-phene-2-carbaldehyde 2,4-dinitro-phenyl-hydrazone

In the approximately planar molecule of the title compound, C(11)H(8)N(4)O(4)S, the dihedral angle between the thio-phene and benzene rings is 5.73 (10)°. In the crystal structure, bifurcated inter/intra-molecular N-H⋯(O,O) hydrogen bonds are present. The intermolecular links lead to inversion dimers containing an R(2) (2)(12) graph-set motif.

But-2-enal 2,4-dinitro-phenyl-hydrazone

In the title compound, C(10)H(10)N(4)O(4), the but-2-enal chain is almost planar, the largest deviation from the mean plane being 0.013 (1) Å, and this plane makes a dihedral angle of 9.95 (24)° with the benzene ring,. Of the two nitro groups, one is twisted with respect to the benzene ring, making a dihedral angle of 5.7 (1)°, whereas the other is nearly in the plane of the benzene ring, with a twist angle of only 0.7 (1)°. This difference is related to the occurence of an intra-molecular N-H⋯O hydrogen bond with the O atom of the less twisted nitro group. The NH group is also involved in a weak inter-action with the same O atom of a symmetry-related mol-ecule, thus forming a pseudo inversion dimer.

(E)-2-Chloro-N'-(2-hydr-oxy-1-naphthyl-methyl-ene)benzohydrazide

In the structue of the title compound, C₁₈H₁₃ClN₂O₂, a new Schiff base, the dihedral angle between the benzene and naphthyl ring system mean planes is 22.5 (2)°. The mol­ecule has an E configuration about the C=N bond, and an intra­molecular hydrogen bond involving the hydoxyl substituent on the naphthyl ring and the N′ atom of the hydrazide. The crystal structure is stabilized by inter­molecular N—H⋯O hydrogen bonds, forming one-dimensional chains running parallel to the a axis.

1-(4-Nitrophenyl)-2-(3-phenylallylidene)hydrazine

In the title compound, C₁₅H₁₃N₃O₂, the nitro­benzene and benzene rings make a dihedral angle of 9.1 (2)°. The crystal structure is consolidated by inter­molecular N—H⋯O hydrogen bonds.

(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.

3-Ethyl-4-[(E)-2-methyl-benzyl-idene-amino]-1H-1,2,4-triazole-5(4H)-thione

Crystals of the title compound, C(12)H(14)N(4)S, were obtained from a condensation reaction of 4-amino-3-ethyl-1H-1,2,4-triazole-5(4H)-thione and 2-methyl-benzaldehyde. In the mol-ecular 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 mol-ecules; 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)-N'-[1-(4-Amino-phen-yl)ethyl-idene]benzohydrazide

Crystals of the title compound, C₁₅H₁₅N₃O, were obtained from a condensation reaction of benzohydrazide and 1-(4-amino­phen­yl)ethanone. The mol­ecule assumes an E configuration with the amino­phenyl and benzohydrazide units located on opposite sites of the C=N double bond. In the crystal structure, the benzene rings of the mol­ecule are slightly twisted with respect to the central hydrazide, the dihedral angles being 18.22 (12) and 27.62 (12)°. The crystal structure contains inter­molecular N—H⋯O and weak C—H⋯N hydrogen bonding.

Methyl 3-[(E)-1-(4-aminophenyl)ethylidene]dithiocarbazate

The title compound, C₁₀H₁₃N₃S₂, was obtained from a condensation reaction of methyl dithio­carbazate and 4-amino­acetophenone. In the crystal structure, the nearly planar mol­ecule assumes an E configuration, the benzene ring and dithio­carbazate group being located on opposite sides of the N=C bond. C—H⋯π inter­actions and N—H⋯S hydrogen bonding are present in the crystal structure.

Methyl 3-[(E)-furfurylidene]dithiocarbazate

The mol­ecule of the title Schiff base compound, C₇H₈N₂OS₂, prepared by the reaction of methyl dithio­carbazate and furfural in an ethanol solution under reflux, adopts an E configuration; the dithio­carbazate and furan units are located on opposite sides of the C=N double bond. The planar dithio­carbazate group is twisted slightly with respect to the furan ring, making a dihedral angle of 5.2 (1)°. Adjacent mol­ecules are linked by N—H⋯S hydrogen bonding to form a supra­molecular dimer across an inversion center.

3-Penta-none 2,4-dinitro-phenyl-hydrazone

Crystals of the title compound, C(11)H(14)N(4)O(4), were obtained from a condensation reaction of 2,4-dinitro-phenyl-hydrazine and 3-penta-none. In the crystal structure, the mol-ecule, except one methyl group, displays a nearly planar structure. The imino group links to the adjacent nitro group via intra-molecular 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 mol-ecules. The crystal structure also contains weak inter-molecular C-H⋯O hydrogen bonding.