Synthesis, crystal structure and spectroscopic and Hirshfeld surface analysis of 4-hy-droxy-3-meth-oxy-5-nitro-benzaldehyde.

The title compound, C8H7NO5, is planar with an r.m.s. deviation for all non-hydrogen atoms of 0.018 Å. An intra-molecular O-H⋯O hydrogen bond involving the adjacent hy-droxy and nitro groups forms an S(6) ring motif. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the bc plane. The layers are linked by a further C-H⋯O hydrogen bond, forming slabs, which are linked by C=O⋯π inter-actions, forming a three-dimensional supra-molecular structure. Hirshfeld surface analysis was used to investigate inter-molecular inter-actions in the solid state. The mol-ecule was also characterized spectroscopically and its thermal stability investigated by differential scanning calorimetry and by thermogravimetric analysis.