Space group revsion of the triclinic polymorph of salicyl­aldehyde azine

The structure of the title compound, C₁₄H₁₂N₂O₂ {systematic name: 2,2′-[hydrazinediylidenebis(methanylyl­idene)]diphen­ol}, has already been determined in the triclinic space group P with Z = 4 [El-Medani, Aboaly, Abdalla & Ramadan (2004). Spectrosc. Lett. 37, 619–632]. However, the correct space group should be P2₁/c with Z = 4. This structure is a new polymorph of the already known monoclinic polymorph of salicyladehyde azine, which crystallizes in space group P2₁/n with Z = 2. The benzene rings form a dihedral angle of 46.12 (9)°. Two intramolucular O—H...N hydrogen bonds occur.

2-Azido-1-(4-fluoro­phen­yl)ethanone

The crystal structure of the title compound, C₈H₆FN₃O, is stabilized by C—H...O hydrogen bonds, which link the mol­ecules into chains running parallel to the a axis.

2-Azido-1-(4-methyl­phen­yl)ethanone

In the mol­ecule of the title compound, C₉H₉N₃O, the angle formed by the least-squares line through the azide group with the normal to the plane of the benzene plane ring is 46.62 (16)°. The crystal structure features C—H...O hydrogen bonds, which link the mol­ecules into zigzag chains running parallel to [010].

2-Azido-1-(4-nitro­phen­yl)ethanone

In the title compound, C₈H₆N₄O₃, the ketone [C—C(=O)—C] and nitro groups are tilted with respect to the benzene ring by 18.92 (6) and 24.11 (15)°, respectively. In the crystal, mol­ecules are linked into inter­woven chains running parallel to the [100] direction by C—H...N hydrogen bonds and weak π–π stacking inter­actions, with centroid–centroid separations of 3.897 (3) Å.

Methyl 2-oxo-2H-chromene-3-carboxyl­ate

The title compound, C₁₁H₈O₄, features an almost planar mol­ecule (r.m.s. deviation = 0.033 Å for all non-H atoms). In the crystal, the mol­ecules are linked via C—H...O hydrogen bonds, forming two-dimensional networks lying parallel to (1-21).

4-Meth­oxy-N-(4-meth­oxy-2-nitro­phen­yl)benzamide

In the title compound, C₁₅H₁₄N₂O₅, the central amide C—C(=O)—N—C unit forms dihedral angles of 28.17 (13) and 26.47 (13)° with the two benzene rings, whereas the two benzene rings are almost coplanar, making a dihedral angle of 4.52 (13)°. The two meth­oxy and the nitro substituents are almost coplanar with their attached benzene rings, with C—O—C—C torsion angles of −1.3 (4) and −4.6 (4)°, and an O—N—C—C torsion angle of 17.1 (3)°. In the crystal, mol­ecules are linked via C—H...O and N—H...O inter­actions, forming a tape running along the b axis.