Crystal structure of (E )-4-{2-[4-(allyloxy)phenyl]diazenyl}benzoic acid

The title compound, C16H14N2O3, has an E conformation about the azobenzene [—N N– = 1.2481 (16) A ˚ ] linkage. The benzene rings are almost coplanar [dihedral angle = 1.36 (7)�]. The O atoms of the carboxylic acid group are disordered over two sets of sites and were refined with an occupancy ratio of 0.5:0.5. The two disordered components of the carboxylic acid group make dihedral angles of 1.5 (14) and 3.8 (12)� with the benzene ring to which they are attached. In the crystal, molecules are linked via pairs of O—H� � �O hydrogen bonds, forming inversion dimers. The dimers are connected via C—H� � �O hydrogen bonds, forming ribbons lying parallel to [120]. These ribbons are linked via C—H� � �� interactions, forming slabs parallel to (001)