Syntheses, crystal structures and Hirshfeld surface analyses of (E)-1-[2,2-di-chloro-1-(2,3-di-meth-oxyphen-yl)ethen-1-yl]-2-phenyl-diazene and (E)-1-(4-chloro-phen-yl)-2-[2,2-di-chloro-1-(2,3-di-meth-oxy-phen-yl)ethen-1-yl]diazene.

The crystal structures and Hirshfeld surface analyses of two similar azo compounds are reported. (E)-1-[2,2-di-chloro-1-(2,3-di-meth-oxy-phen-yl)ethen-1-yl]-2-phenyl-diazene, C16H14Cl2N2O2, (I), crystallizes in space group P21/c with Z = 4, and (E)-1-(4-chloro-phen-yl)-2-[2,2-di-chloro-1-(2,3-di-meth-oxy-phen-yl)ethen-1-yl]diazene, C16H13Cl3N2O2, (II), in the space group P1 with Z = 4. In the crystal structure of (I), the mol-ecules form layers parallel to the (010) plane through C-H⋯π and C-Cl⋯π inter-actions and van der Waals inter-actions between these layers consolidate the packing. There are two symmetry-independent mol-ecules in the asymmetric unit of (II). In the crystal, mol-ecules are connected by C-H⋯O and C-H⋯Cl hydrogen bonds, forming a three-dimensional network. C-Cl⋯π inter-actions also contribute to the packing. The inter-molecular contacts in the crystals (I) and (II) were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.