Crystal structures and Hirshfeld surface analyses of the two isotypic compounds ()-1-(4-bromo-phen-yl)-2-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]diazene and ()-1-(4-chloro-phen-yl)-2-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]diazene.

In the two isotypic title compounds, CHBrClNO, (), and CHClNO, (), the substitution of one of the phenyl rings is different [Br for () and Cl for ()]. Aromatic rings form dihedral angles of 60.9 (2) and 64.1 (2)°, respectively. Mol-ecules are linked through weak ⋯Cl contacts [ = Br for () and Cl for ()], C-H⋯Cl and C-Cl⋯π inter-actions into sheets parallel to the plane. Additional van der Waals inter-actions consolidate the three-dimensional packing. Hirshfeld surface analysis of the crystal structures indicates that the most important contributions for the crystal packing for () are from C⋯H/H⋯C (16.1%), O⋯H/H⋯O (13.1%), Cl⋯H/H⋯Cl (12.7%), H⋯H (11.4%), Br⋯H/H⋯Br (8.9%), N⋯H/H⋯N (6.9%) and Cl⋯C/C⋯Cl (6.6%) inter-actions, and for (), from Cl⋯H / H⋯Cl (21.9%), C⋯H/H⋯C (15.3%), O⋯H/H⋯O (13.4%), H⋯H (11.5%), Cl⋯C/C⋯Cl (8.3%), N⋯H/H⋯N (7.0%) and Cl⋯Cl (5.9%) inter-actions. The crystal of (I) studied was refined as an inversion twin, the ratio of components being 0.9917 (12):0.0083 (12).