Crystal structure of 2-{(R)-[1-(4-bromophenyl)ethyl]iminomethyl}-4-(phenyldiazenyl)phenol, a chiral photochromic Schiff base

The title chiral photochromic Schiff base compound, C₂₁H₁₈BrN₃O, was synthesized from (R)-(+)-1-(4-bromophenyl)ethylamine and the salicylaldehyde of an azobenzene derivative. The molecule corresponds to the phenol-imine tautomer, the C=N and N - C bond distances being 1.285 (3) and 1.470 (3) Å, respectively. The diazenyl group adopts a trans form, with an N=N distance of 1.256 (3) Å. The hydroxy group is involved in intramolecular O - H⋯N hydrogen bonding. In the crystal, C - H⋯π interactions consolidate the crystal packing of one-dimensional chains, which exhibits short intermolecular Br⋯C contacts of 3.400 (3) Å.