Crystal structure and Hirshfeld surface analysis of 1-[(E)-2-(3-nitro-phen-yl)diazen-1-yl]naphthalen-2-ol.

The title compound, C(16)H(11)N(3)O(3), belongs to the family of azo dyes. In the light of a single-crystal X-ray study, it is evident that of the tautomeric forms (azo-hydrazone), the hydrazone form is the predominant form in the solid state, namely, (1E)-1-[2-(3-nitro-phen-yl)hydrazin-1-yl-idene]-1,2-di-hydro-naphthalen-2-one. The naphthol and benzene fragments attached to the -N=N- moiety adopt the s-trans conformation. Furthermore, the mol-ecules are nearly coplanar, subtending a dihedral angle of 2.63†(5)°. An intra-molecular N-H⋯O hydrogen bond occurs. There are only two types of inter-molecular inter-actions in the crystal structure: strong hydrogen-bonding C-H⋯O inter-actions and π-π stacking inter-actions. The importance of C-H⋯O inter-actions in the mol-ecular packing is reflected by the relatively high contributions (28.5%) made by O⋯H/H⋯O contacts to the Hirshfeld surface.