4-[(2-Chlorophenyl)diazenyl]-6-methoxy-2-[[tris(hydroxymethyl)methyl]aminomethylene]cyclohexa-3,5-dien-1(2H)-one.

The structure of the title compound, C(18)H(20)ClN(3)O(5), displays the characteristic features of azobenzene derivatives. Intramolecular N-H.O, weak intramolecular C-H.O, and intermolecular O-H.O and C-H.O interactions influence the conformation of the molecules and the crystal packing. Intermolecular hydrogen bonds link the molecules into infinite chains, and the title compound adopts the keto-amine tautomeric form. The azobenzene moiety of the molecule has a trans configuration. The molecule is not planar, and the dihedral angle between the two phenyl rings is 35.6 (2) degrees.