2-{(E)-1-[2-(2-Nitro-phen-yl)hydrazin-1-yl-idene]eth-yl}benzene-1,3-diol mono-hydrate.

The hydrazone mol­ecule in title monohydrate, C14H13N3O4·H2O, is almost coplanar, the dihedral angle between the terminal benzene rings being 3.22 (15)°; the nitro group is coplanar with the benzene ring to which it is bonded [O—N—C—C = −2.8 (4)°]. The hy­droxy group forms an intra­molecular hydrogen bond with the imine N atom, and the conformation about the imine bond [1.305 (3) A] is E. In the crystal, supra­molecular layers in the (203) plane are connected into a double layer via water–nitro O—H⋯O hydrogen bonds, along with π–π inter­actions [ring centroid–centroid distance = 3.7859 (19) A].