Crystal structure of 1-[(Z)-2-phenyl-hydrazin-1-yl-idene]naphthalen-2(1H)-one.

In the title compound, C16H12N2O, the dihedral angle between the planes of the benzene ring and naphthalenone ring system is 1.89 (8)°; an intra-molecular N-H⋯O hydrogen bond occurs between the imino group and the carbonyl group. In the crystal, mol-ecules are linked by weak C-H⋯π inter-actions into supra-molecular chains propagating along the [01-1] direction.

1-[(E)-2-(2-Hy-droxy-5-methyl-phen-yl)diazen-2-ium-1-yl]naphthalen-2-olate.

The title zwitterion, C17H14N2O2, crystallizes with two independent mol-ecules in the asymmetric unit, both of which are approximately planar, the dihedral angles between the benzene ring and the naphthalene ring system being 4.39 (12)° in one mol-ecule and 5.83 (12)° in the other, and show an E conformation with respect to the azo double bond.

(E)-1-[(2,4,6-Tri-bromo-phen-yl)diazen-yl]naphthalen-2-ol.

The title azo mol-ecule, C16H9Br3N2O, adopts a trans conformation with respect to the azo N=N double bond. An intra-molecular O-H⋯N hydrogen bond forms an S(6) ring motif. The dihedral angle between the naphthalene ring system and the benzene ring is 33.

(E)-1-(3-Formyl-phen-yl)-2-(2-oxidonaphthalen-1-yl)diazen-1-ium.

In the title zwitterion, C17H12N2O2, the dihedral angle between the benzene ring and naphthalene ring system is 11.76 (7)° and an intra-molecular N-H⋯O hydrogen bond exists. In the crystal, molecules are linked via pairs of C-H⋯O hydrogen bonds, forming inversion dimers.

(E)-1-(3-Chloro-phen-yl)-2-(2-oxidonaphthalen-1-yl)diazen-1-ium.

The title zwitterion,, C16H11ClN2O, is approximately planar, the dihedral angle between the benzene ring and naphthalene ring system is 1.55 (13)°; an intra-molecular N-H⋯O hydrogen bond stabilizes the planar conformation. In the crystal, π-π stacking between the benzene ring and the naphthalene ring system of adjacent mol-ecules links the mol-ecules into supra-molecular chains running along the b axis, the centroid-centroid distance being 3.