Key indicators: single-crystal X-ray study; T = 150 K; mean (C-C) = 0.004 Å; R factor = 0.043; wR factor = 0.120; data-to-parameter ratio = 12.8.The title compound, C 18 H 14 N 2 O 2 , 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-HÁ Á ÁO hydrogen bond forms an S(6) ring motif. In the crystal, molecules are linked via C-HÁ Á ÁO hydrogen bonds, forming -A-A-A-and -B-B-B-chains parallel to one another and propagating along the a-axis direction. There are alsointeractions 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].
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In the title compound, C16H12N2O2·0.5CH3OH, the H atom of the –OH group has been transfered to the N atom in the azo group, forming a zwitterion. Hence, there is an intramolecular N—H⋯O, rather than an O—H⋯N, hydrogen bond in the molecule. The molecule is almost planar, the dihedral angle between the benzene ring and the mean plane of the naphthalene ring system being 4.51 (6)°. In the crystal, molecules are linked to and bridged by O—H⋯O hydrogen bonds involving the methanol molecule, which is located about a twofold rotation axis, and hence half-occupied, forming zigzag chains along [001]. Molecules are also linked via C—H⋯π and π–π interactions, the latter involving adjacent benzene and naphthalene rings and having a centroid–centroid distance of 3.6616 (13) Å, forming a three-dimensional network.
In the title compound, C16H12N2O, the dihedral angle between the planes of the benzene ring and naphthalenone ring system is 1.89 (8)°; an intramolecular N—H⋯O hydrogen bond occurs between the imino group and the carbonyl group. In the crystal, molecules are linked by weak C—H⋯π interactions into supramolecular chains propagating along the [01-1] direction.
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