The title Schiff base compound, C13H9ClN4O5 center dot 0.5CH(3)CN, crystallizes as an acetonitrile hemisolvate; the solvent molecule being located on a twofold rotation axis. The molecule is nearly planar, with a dihedral angle between the two benzene rings of 3.7 (2)degrees. The configuration about the C=N bond is E, and there is an intramolecular N-H center dot center dot center dot O-nitro hydrogen bond present forming an S(6) ring motif. In the crystal, molecules are linked by O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds, forming layers lying parallel to (10 (1) over bar). The layers are linked by C-H center dot center dot center dot Cl hydrogen bonds, forming a supramolecular framework. Within the framework there are offset pi-pi stacking interactions [intercentroid distance = 3.833 (2) angstrom] present involving inversion-related molecules. The DFT study shows that the HOMO and LUMO are localized in the plane extending from the phenol ring to the 2,4-dinitrobenzene ring, and the HOMO-LUMO gap is found to be 0.13061 a.u.