6-Chloro-8-nitro-4-oxo-4H-chromene-3-carbaldehyde.

In the title compound, C10H4ClNO5, the non-H atoms of the 6-chloro-chromone unit are coplanar (r.m.s. deviation = 0.017 Å) with the largest deviation from the mean plane [0.031 (2) Å] being found for the C=O C atom. The nitro group (NO2) is inclined to the chromone unit mean plane by 13.3 (2) °. The formyl group is also twisted with respect to the attached ring [C-C-C-O torsion angles = 10.8 (4) and -171.8 (2)°]. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds forming slab-like networks lying parallel to (-301). The slabs are linked by π-π inter-actions involving the benzene rings of the chromone units [centroid-centroid distance = 3.770 (3) Å].