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

The hydrazone mol-ecule in title monohydrate, C(14)H(13)N(3)O(4)·H(2)O, 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 hy-droxy group forms an intra-molecular hydrogen bond with the imine N atom, and the conformation about the imine bond [1.305 (3) Å] is E. In the crystal, supra-molecular layers in the (203) plane are connected into a double layer via water-nitro O-H⋯O hydrogen bonds, along with π-π inter-actions [ring centroid-centroid distance = 3.7859 (19) Å].