The unit-cell dimensions and space group of the second monoclinic polymorph of the title compound, C₁₅H₁₁FO, differ from those of the previously reported form [Jing (2009). Acta Cryst. E65, o2515]. The title compound shows an E conformation of the C=C bond with the 4-fluoro­phenyl group opposite to the benzoyl group. The torsion angle of between the planes of the 4-fluoro­phenyl and benzoyl groups is 10.53 (6)°. In the crystal, weak C—HO and C—HF inter­actions form a cross-linked packing motif, building sheets parallel to (-102).

The asymmetric unit of the title compound, C₁₃H₁₁NO₆, contains two mol­ecules in both of which the six-membered 1,3-dioxane-4,6-dione ring shows a screw-boat conformation. The dihedral angles between the best planes through the six-membered rings are 47.8 (2) and 49.8 (2)°. In the crystal, C—HO inter­actions link the mol­ecules, building a supramolecular sheet parallel to the c axis.

In the title zwitterionic compound, C₁₅H₁₉NO₂S, the six-membered heterocycle adopts a sofa conformation. The negative charge is delocalized along the carbonyl and enolate system on the ring and the positive charge is localized on the S atom. Two inter­molecular C—HO inter­actions help to establish the packing.

In the zwitterionic title compound, C₉H₁₃NO₂S, the pyrrolidine heterocycle adopts an envelope conformation (with the C atom in the 7-position as the flap). The negative charge is delocalized over the two carbonyl groups and the C atom connecting them. The positive charge is located on the S atom. Two inter­molecular C—HO inter­actions are observed. The molecular geometry at the S atom is trigonal pyramidal.

In the title compound, C₂₁H₁₇NS, the C=N double bond shows an E conformation. The dihedral angle between the mean planes of the naphthyl residue and the benzo­thio­phene residue is 89.14 (6)°. The crystal packing is stabilized by inter­molecular C—Hπ inter­actions, building a ribbon structure along the a axis.

In the title compound, C₂₁H₂₄O₅, the dihedral angle between the benzene rings is 19.57 (15)°. In the crystal, the mol­ecular arrangement makes up head-to-head centrosymmetric dimers assembled by pairs of O—HO bonds; this arrangement builds a graph-set ring motif of R²₂(8). The dimers are linked into a tape running along the b-axis direction through C—HO inter­actions. The packing is further consolidated by C—Hπ inter­actions, forming layers parallel to (10-2).

The asymmetric unit of the title compound, C₁₉H₁₅N₃O₂, contains two mol­ecules, both of which show an E conformation of the imine bond. The dihedral angles between the phenyl rings in the phenyl­hydrazine groups are 86.09 (6) and 83.41 (5)° in the two mol­ecules. The 4-nitrobenzene rings show torsion angles of 4.4 (2) and 10.9 (2)° from the two C=N—N planes. In the crystal, C—Hπ inter­actions and C—HO hydrogen bonds are observed growing along the a, b and c axes, resulting in a complex supramolecular array.

In the title compound, C₂₁H₂₆N₂O₃, the morpholine ring has a chair conformation and the dihedral angle between the two phenyl rings is 59.0 (3)°. The crystal packing is stabilized by inter­molecular O—HO hydrogen bonds, generating a ribbon structure along the a axis. An intra­molecular N—HO contact is also present.

The asymmetric unit of the title compound, C₂₁H₂₀N₂, contain two mol­ecules, both of them showing an E configuration of the C=N bond. The dihedral angles between the phenyl rings in the phenyl­hydrazone groups are 86.84 (10) and 84.85 (8)° for the two mol­ecules. Inter­molecular C—Hπ inter­actions are observed in the crystal structure.

In the title compound, C₁₁H₁₅FN₂O₅, the five-membered ring has an envelope conformation, while the six-membered ring is essentially planar, with a maximum deviation of 0.032 (2) Å from the mean plane. The crystal packing is stabilized by inter­molecular N—HO and O—HO hydrogen bonds, generating a layer structure parallel to (001).

The title compound, C₂₃H₁₇N₃O₃, has an E configuration with respect to the C=N bond. The dihedral angle between the two phenyl rings bonded to the hydrazine group is 86.45 (13)°. The furan ring makes dihedral angles of 3.4 (2) and 7.06 (13)°, respectively, with the methyl­idenehydrazine C=N-N plane and the benzene ring.

In the crystal structure of the title compound, C₂₆H₂₂N₄, the mol­ecule is located on an inversion centre and shows an E configuration with respect to each C=N bond. The dihedral angle between the phenyl rings in the diphenyl­hydrazone group is 83.69 (11)°. These two rings make dihedral angles of 30.53 (15) and 84.53 (16)° with the central N—N=C—C=N—N dihydrazonoethane plane. Inter­molecular C—Hπ inter­actions are observed.

The asymmetric unit of the title compound, C₁₉H₁₆N₂, contains two independent mol­ecules, both of which show an E configuration with respect to the C=N bond. The dihedral angles between the phenyl rings bonded to the hydrazine group are 81.00 (10) and 88.34 (8)° in the two mol­ecules. Inter­molecular C—Hπ inter­actions are observed in the crystal structure.

The title compound, C₂₂H₂₀Br₂N₂S, was synthesized under solvent-free conditions. The mol­ecule shows crystallographic C₂ symmetry, with the S atom of the central thio­phene ring lying on a twofold rotation axis. Furthermore, as a consequence of the (S,S) stereochemistry, the mol­ecule has a twisted conformation. The dihedral angle between the thio­phene and benzene rings is 72.7 (2)° and that between the two benzene rings is 55.9 (2)°. In the crystal, mol­ecules are arranged in a chevron-like pattern, without any significant inter­molecular inter­actions.

In the title compound, C₁₅H₂₀O₅S, the tetra­hydro­furan ring shows an envelope conformation. The crystal packing is stabilized by an inter­molecular O—HO hydrogen bond, generating a ribbon structure along the a axis. Two weak inter­molecular C—HO inter­actions are also observed.

In the title compound, C₁₈H₁₈N₂O, the dihedral angle between the indole system and the phenyl ring is 17.2 (2)°. The crystal packing features two N—HO hydrogen bonds, which link the mol­ecules into layers parallel to (001). The absolute configuration was determined by the synthetic procedure and was set according to the starting material.