In the title compound, C(18)H(14)BrNO, the naphthalene ring system [maximum deviation = 0.015 (3) Å] forms a dihedral angle of 67.70 (10)° with the benzene ring. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds into C(4) chains propagating in [100]. A C-H⋯O inter-action reinforces the chain connectivity, generating an R(2) (1)(6) loop.

The mol-ecule of the title compound, C(21)H(16)N(2)O, exists in the keto form and the C=O and N-H bonds are mutually cis in the crystal structure, although an enol form would be possible through tautomerism. The dihedral angle between the quinoline and the naphthalene systems is 22.04 (2)°. A bifurcated intramolecular N-H⋯(O,N) hydrogen bond is present.

In the title compound, C(15)H(12)N(2)OS, the naphthalene ring system [maximum deviation = 0.026 (1) Å] forms a dihedral angle of 85.69 (6)° with the thia-zole ring [maximum deviation = 0.010 (1) Å]. In the crystal, inversion dimers linked by pairs of N-H⋯N hydrogen bonds generate R(2) (2)(8) loops. The dimers are linked by C-H⋯O hydrogen bonds into chains propagating along [110].

The title Schiff base, C18H15NO, crystallizes in its zwitterionic form and an N-H⋯O hydrogen bond closes an S(6) ring. The dihedral angle between the aromatic ring systems is 36.91 (10)°. Weak aromatic π-π stacking occurs in the crystal [minimum centroid-centroid separation = 3.7771 (15) Å].

The title Schiff base compound, C(17)H(13)N(3)O(3), crystallizes in a zwitterionic form and exists in a trans configuration about the C=N bond. The mol-ecule is slightly twisted, the dihedral angle between the benzene ring and naphthalene ring system being 10.80 (9)°. The nitro group is twisted relative to the plane of the benzene ring [dihedral angle = 8.88 (12)°]. Bifurcated intra-molecular N...

The mol-ecule of the title compound, C(23)H(17)NO(2), a Schiff base derived from 2-hydr-oxy-1-naphthaldehyde, crystallizes in the keto-amine tautomeric form. The dihedral angle between the aniline and hydroxy-benzene rings is 77.41 (17)°, whereas the planes of the naphthaldehyde and fused aniline benzene rings are nearly coplanar, making a dihedral angle of 8.29 (15)°. Intra-molecular N-H⋯O hyd...