Crystal structures and Hirshfeld surface analyses of methyl 4-{2,2-di­chloro-1-[(E)-phenyl­diazen­yl]eth­enyl}benzoate, methyl 4-{2,2-di­chloro-1-[(E)-(4-methyl­phen­yl)diazen­yl]ethen­yl}benzoate and methyl 4-{2,2-di­chloro-1-[(E)-(3,4-di­methyl­phen­yl)diazen­yl]ethen­yl}benzoate

The crystal structures and Hirshfeld surface analyses of three similar azo compounds are reported. Methyl 4-{2,2-dichloro-1-[(E)-phenyldiazenyl]ethenyl}benzoate, C16H12Cl2N2O2, (I), and methyl 4-{2,2-dichloro-1-[(E)-(4-methylphenyl)diazenyl]ethenyl}benzoate, C17H14Cl2N2O2, (II), crystallize in the space group P21/c with Z = 4, and methyl 4-{2,2-dichloro-1-[(E)-(3,4-dimethylphenyl)diazenyl]ethenyl}benzoate, C18H16Cl2N2O2, (III), in the space group P\overline{1} with Z = 2. In the crystal of (I), molecules are linked by C—H⋯N hydrogen bonds, forming chains with C(6) motifs parallel to the b axis. Short intermolecular Cl⋯O contacts of 2.8421 (16) Å and weak van der Waals interactions between these chains stabilize the crystal structure. In (II), molecules are linked by C—H⋯O hydrogen bonds and C—Cl⋯π interactions, forming layers parallel to (010). Weak van der Waals interactions between these layers