Received 19 May 2013
The title compound, C18H14N2O2, crystallized with two independent zwitterion molecules (A and B) in the asymmetric unit. They are both close to planar, the dihedral angle between the benzene ring and naphthalene ring system being 4.30 (9)° in A and 4.69 (9)° in B. Each molecule has an E conformation with respect to the azo double bond. In each of the independent molecules, an intramolecular N-HO hydrogen bond forms an S(6) ring motif. In the crystal, molecules are linked via C-HO hydrogen bonds, forming -A-A-A- and -B-B-B- chains parallel to one another and propagating along the a-axis direction. There are also - interactions between adjacent molecules involving benzene and naphthalene rings [centroid-centroid distance of 3.626 (3) Å for adjacent A molecules and 3.652 (3) Å for adjacent B molecules].
For general background to azo compounds and their use in dyes, pigments and advanced materials, see: Lee et al. (2004); Oueslati et al. (2004). Many azo compounds have been synthesized by diazotization and diazo coupling reactions, see: Wang et al. (2003). For a related structure, see: Rãdulescu et al. (2006).
Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 2012).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2604 ).
We thank all researchers of the CHEMS Research Unit of the University of Constantine, Algeria, for the valuable assistance they have provided us throughout the realisation of this work. We also thank Dr. L. Ouahab, Director of Research at the Laboratory UMR LCSIM 6511, CNRS, Rennes I (France), for his valuable collaboration in the data collection and analysis.
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