The title compound, C19H14F3NO2, crystallizes in the keto–amine tautomeric form, with a strong intra­molecular N—H⋯O hydrogen bond. The mol­ecule is almost planar; the dihedral angle between the naphthalene ring system and the benzene ring is 4.60 (7)°. In the crystal, mol­ecules are linked into chains along the c axis by C—H⋯O hydrogen bonds. The F atoms of the trifluoro­methyl group are disordered over two positions with refined site occupancies of 0.668 (9) and 0.332 (9).

In the title compound, C21H21NO, the dihedral angle between the naphthalene ring system and the benzene ring is 64.61 (6)°. The mol­ecular structure is stabilized by an intra­molecular C—H⋯N hydrogen bond.

The title mol­ecule, C12H10N2O3S, is nonplanar with an inter­planar angle of 33.44 (7)° between the benzene and thio­phene rings. In the crystal there exist only weak inter­molecular C—H⋯O inter­actions, π–π inter­actions between the benzene rings [centroid–centroid distance = 3.7465 (14) Å] and X—Y⋯π inter­actions to the thio­phene and benzene rings [N⋯centroid distances = 3.718 (3) and 3.355 (3) Å, respectively]. Inter­molecular C—H⋯O inter­actions link the mol­ecules into chains parallel to the a axis.

In the title mol­ecule, C17H12INO, the dihedral angle between the naphthaldeyde plane and the 3-iodo­aniline plane is20.07 (13)°. It exists in the solid state as an enol–imine tautomer with a strong intra­molecular O—H⋯N hydrogen bond.

The title compound, C17H12BrNO, exists in an enol–imine form and the mol­ecular structure features an intra­molecular O—H⋯N hydrogen bond. The dihedral angle between the benzene ring and the naphthalene ring system is 17.27 (15)°.

In the title compound, C12H10N2O3S, the dihedral angle between the benzene and thio­phene rings is 43.17 (4)°. The crystal structure is devoid of any hydrogen-bonding inter­actions. However, π–π inter­actions between the benzene and thio­phene rings [distance between ring centroids = 3.6850 (11) Å] stack the mol­ecules along the a axis. The absolute structure could not be determined as the crystal studied was a racemic twin with a BASF parameter of 0.31 (6).

The title Schiff base compound, 0.57C17H12FNO·0.43C17H12FNO, reveals both the enol (OH) and keto (NH) tautomeric forms with occupancies of 0.57 (6) and 0.43 (6), respectively. The tautomeric forms are stabilized by intra­molecular O—H⋯N (enol) and N—H⋯O (keto) hydrogen bonds. The dihedral angle between the naphthalene ring system and the benzene ring is 32.76 (1)°.

The title compound, C14H9ClF3NO2, crystallizes in a phenol–imine tautomeric form, with a strong intra­molecular O—H⋯N hydrogen bond. The dihedral angle between the two benzene rings is 47.62 (9)°. In the crystal, mol­ecules are linked into chains along the c axis by C—H⋯O hydrogen bonds, and weak C—H⋯π inter­actions involving both benzene rings are also observed.

The mol­ecule of the title compound, C16H17N3O5S, crystallizes in a zwitterionic form, with a strong intra­molecular N—H⋯O hydrogen bond. The dihedral angle between the two benzene rings is 7.06 (9)°. In the crystal, mol­ecules are linked into chains along the c axis by inter­molecular N—H⋯O hydrogen bonds.

In the title compound, C21H12ClN3O, the phenoxy ring makes dihedral angles of 51.42 (5) and 65.01 (6)°, respectively, with the chlorophenyl and phthalonitrile rings. In the crystal structure, the mol­ecules are inter­linked through weak C—H⋯N and C—H⋯π contacts, and π–π stacking inter­actions via crystallographic inversion centres form a three-dimensional network. The distance between the centroids of the phthalonitrile rings is 3.9104 (11)Å, with a slippage between the rings of 1.626 Å and a perpendicular distance between the rings of 3.556 Å.

The title compound, C12H12Cl2N2O3, crystallizes as a non-merohedral twin with a twinning ratio of 0.51:0.49. The mol­ecule adopts a keto–hydrazo tautomeric form stabilized by an intra­molecular N—H⋯O hydrogen bond. The configuration around the N—N bond is trans.