The aromatic rings in the title compound, C13H8ClNO4, enclose a dihedral angle of 39.53 (3)°. The nitro group is almost coplanar with the ring to which it is attached [dihedral angle = 4.31 (1)°]. In the crystal, mol­ecules are connected by C—H⋯O hydrogen bonds into chains running along [001].

The asymmetric unit of the title compound, C17H18N2O4, contains two independent mol­ecules (A and B) differing principally in the conformations of the alkyl chains, anti for molecule A and gauche for molecule B. The dihedral angles between the aromatic rings are 82.51 (6) and 82.25 (6)° in the two molecules. In the crystal, amide–amide inter­actions (as N—H⋯O=C) results in distinct chains of A and B mol­ecules running parallel to the a-axis direction. C—H⋯O inter­actions also occur.

The asymmetric unit of the title compound, C14H12N2O4, contains two mol­ecules that differ principally in the orientation of the acetamide substituent to the adjacent benzene ring with dihedral angles of 44.77 (7) and 19.06 (7)°. The dihedral angles between the benzene rings are 64.46 (4) and 80.84 (4)°. In the crystal, classical N—H⋯O hydrogen bonds form C(4) chains along [100]. These chains are inter­linked by C—H⋯O contacts forming R 2 2(10) rings. In the crystal, π–π inter­actions are observed with a distance of 3.5976 (18) Å between the centroids of the nitro-substituted benzene rings of one type of mol­ecule.

The crystal structure of the title compound, C14H15NO·0.5H2O, features N—H⋯O and O—H⋯N hydrogen bonds between the amino group and water molecule of crystallization, which generate a chain along the c axis. The water mol­ecule lies on a twofold rotation axis. A C—H⋯π inter­action is observed between the phenyl and aniline rings. The angle between the mean planes of the phenyl rings is 72.51 (7)°.

In the title compound, C19H16N2O3S·C2H6O, the 4-hy­droxy­benzyl­idene group is oriented at dihedral angles of 73.17 (7) and 77.06 (7)° with respect to the aniline groups. The sulfonyl group make dihedral angles of 44.89 (13) and 59.16 (12)° with the adjacent aniline groups. In the crystal, a two-dimensional polymeric network parallel to (010) is formed by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds. There also exist π–π inter­actions with a distance of 3.5976 (18) Å between the centroids of hy­droxy­phenyl rings.

Mol­ecules of the title compound, C20H14O2, show approximate C s symmetry with the approximate mirror plane perpendicular to the central ring. The torsion angles about the acyclic bonds are 30.05 (15) and 30.77 (15)° in one half compared to −36.62 (14) and −18.60 (15)° in the other half of the mol­ecule. The central aromatic ring makes dihedral angles of 47.78 (4) and 51.68 (3)° with the two terminal rings.

The crystal structure of the title compound, C10H13NO4, features inter­molecular O—H⋯O(nitro) hydrogen bonding, which links mol­ecules into supra­molecular chains running parallel to the bc diagonal. There is also π–π stacking between 4-nitro­phenyl groups, the inter­planar distance between the nitro­benzene rings being 3.472 (2) Å.

In the title compound, C17H11NO4, the dihedral angle between the two benzene rings is 8.66 (3)°. The nitro group is twisted by 4.51 (9)° out of the plane of the aromatic ring to which it is attached. The presence of inter­molecular C—H⋯O contacts in the crystal structure leads to the formation of chains along the c axis.

In the title compound, C27H19N3O4, the phenol and pyrazole rings are almost coplanar [dihedral angle = 0.95 (12)°] due to an intra­molecular O—H⋯N hydrogen bond, whereas the phenyl ring is tilted by 40.81 (7)° with respect to the plane of the pyrazole ring. The aromatic ring with a nitro­phen­oxy substituent makes a dihedral angle of 54.10 (7)° with the pyrazole ring.

The dihedral angle between the two benzene rings in the title compound, C15H15NO2, is 65.28 (12)°. The crystal structure is stabilized by N—H⋯N and N—H⋯O hydrogen bonds, leading to the formation of supra­molecular chains along the a-axis direction.

The title compound, C22H28N2O6, crystallizes with four half-mol­ecules in the asymmetric unit: each mol­ecule is located about a crystallographic inversion centre. The central methyl­ene groups of two mol­ecules are disordered over two sets of equally occupied sites. The crystal packing is characterized by sheets of mol­ecules parallel to (14).

The title compound, C14H11NO4, crystallizes with two mol­ecules in the asymmetric unit. The major conformational difference between these two mol­ecules is the dihedral angle between the aromatic rings, namely 36.99 (5) and 55.04 (5)°. The nitro groups are coplanar with the phenyl rings to which they are attached, the O—N—C—C torsion angles being −1.9 (3) and 1.0 (3)° in the two mol­ecules.

In the title compound, C27H20F6N2O2, the dihedral angles between the planes of the aromatic rings connected by the ether O atoms are 84.13 (8) and 75.06 (9)°. The crystal structure is stabilized by N—H⋯O and N—H⋯F hydrogen bonds.

The title compound, C12H17NO4, features an almost planar mol­ecule (r.m.s. deviation for all non-H atoms = 0.070 Å). All methyl­ene C—C bonds adopt an anti­periplanar conformation. In the crystal structure the mol­ecules lie in planes parallel to (12) and the packing is stabilized by O—H⋯O hydrogen bonds.

The complete molecule of the title compound, C18H24N2O2, is generated by a crystallographic inversion centre. The torsion angles in the hexa­methyl­ene chain are consistent with an anti­periplanar conformation, whereas the conformation of the O—CH2—CH2—CH2 unit is gauche. The three-dimensional crystal packing is stabilized by N—H⋯O and N—H⋯N hydrogen bonding.

The title compound, C17H18N2O6, crystallizes with two mol­ecules in the asymmetric unit. In both molecules, one of the C—C bonds of the penta­methyl­ene chain connecting the two aromatic rings is in a trans conformation and another displays a gauche conformation. The aromatic rings within each mol­ecule are nearly coplanar [dihedral angles = 3.36 (9) and 4.50 (9)°] and the nitro groups are twisted slightly out of the planes of their attached rings [dihedral angles = 8.16 (3)/6.6 (2) and 4.9 (4)/3.8 (3)°].

The two phenyl rings of the biphenyl unit of the title compound, C18H13NO3, are almost coplanar [dihedral angle 6.70 (9)°]. The nitro­phenyl ring, on the other hand, is significantly twisted out of the plane of the these two rings, making dihedral angles of 68.83 (4)° with the middle ring and 62.86 (4)° with the end ring. The nitro group is twisted by 12.1 (2)° out of the plane of the phenyl ring to which it is attached.

In the title compound, C13H10N2O2, a Schiff base derivative, the dihedral angle between the two aromatic rings is 31.58 (3)°. The C=N double bond is essentially coplanar with the nitro­phenyl ring. The torsion angle of the imine double bond is 175.97 (13)°, indicating that the C=N double bond is in a trans configuration. The crystal structure is stabilized by C—H⋯O contacts and π–π inter­actions (centroid–centroid distances of 3.807 and 3.808Å).

The title compound, C15H14N2O4, is an important inter­mediate for the synthesis of thermotropic liquid crystals. The dihedral angle between the two aromatic rings is 84.29 (4)°. An N—H⋯O hydrogen bond connects the mol­ecules into chains running along the b axis. In addition, the crystal packing is stabilized by weak C—H⋯O hydrogen bonds.

In the title compound, C27H16F6N2O6, the nitro groups are almost coplanar with the aromatic rings to which they are attached [dihedral angles = 3.5 (5) and 6.2 (3)°]. The dihedral angles between adjacent aromatic rings are 78.07 (8) and 71.11 (8)° for nitro­phen­yl/phenyl and 69.50 (8)° for phen­yl/phenyl. An inter­molecular C—H⋯π inter­action seems to be effective in the stabilization of the structure.

The mol­ecule of the title compound, C14H16N2O2, is located on a crystallographic twofold rotation axis. The central O—C—C—O bridge adopts a gauche conformation. One of the amine H atoms is disordered over two equally occupied positions. The crystal structure is stabilized by N—H⋯O and N—H⋯N hydrogen bonds.

The title compound, C18H16N2O2, is a precusor for the synthesis of polyimides. The mol­ecule is located on a crystallographic inversion center and the terminal amino­phen­oxy rings are almost perpendicular to the central benzene ring with a dihedral angle of 85.40 (4)°. The mol­ecular conformation is stabilized by N—H⋯O and N—H⋯N inter­molecular hydrogen-bonding inter­actions.