N,N-dimethyl-N'-[(1E,2E)-3-(4-nitrophenyl)prop-2-enylidene]benzene-1,4-diamine and N,N-dimethyl-4-[(1E,3E)-4-(4-nitrophenyl)buta-1,3-dienyl]-1-naphthylamine.

Syntheses and X-ray structural investigations have been carried out for the two title compounds, viz. C(17)H(17)N(3)O(2), (I), and C(22)H(20)N(2)O(2), (II). The molecular skeleton of (I) is slightly non-planar; the dihedral angles between the conjugated linkage and the p-(dimethylamino)phenyl ring, and between the linkage and the p-nitrophenyl ring are 13.0 (2) and 13.8 (2) degrees, respectively. The dihedral angle between the slightly pyramidal dimethylamine substituent and the aromatic ring is 23.3 (1) degrees. The molecular skeleton of (II) is not planar; the dihedral angles between the conjugated linkage and the naphthalene ring, and between the linkage and the substituted phenyl ring are 36.1 (2) and 2.7 (3) degrees, respectively. The dimethylamine substituent in (II) has a pyramidal geometry; the dihedral angle between this substituent and the naphthalene ring is 71.7 (1) degrees. The dihedral angle between the nitro group and the plane of the substituted phenyl ring is 9.0 (3) degrees. There is a weak intermolecular C-H.O hydrogen bond in the crystal structure of (II), which links the molecules into centrosymmetric dimers. Molecular mechanics calculations of molecular conformations have shown that the crystal environment influences the conformation more in (I) than in (II).