Crystal structures and Hirshfeld surface analyses of methyl 4-{2,2-di-chloro-1-[()-phenyl-diazen-yl]eth-enyl}benzoate, methyl 4-{2,2-di-chloro-1-[()-(4-methyl-phen-yl)diazen-yl]ethen-yl}benzoate and methyl 4-{2,2-di-chloro-1-[()-(3,4-di-methyl-phen-yl)diazen-yl]ethen-yl}benzoate.

The crystal structures and Hirshfeld surface analyses of three similar azo compounds are reported. Methyl 4-{2,2-di-chloro-1-[()-phenyl-diazen-yl]ethen-yl}benzoate, CHClNO, (), and methyl 4-{2,2-di-chloro-1-[()-(4-methyl-phen-yl)diazen-yl]ethen-yl}benzoate, CHClNO, (), crystallize in the space group 2/ with = 4, and methyl 4-{2,2-di-chloro-1-[()-(3,4-di-methyl-phen-yl)diazen-yl]ethen-yl}benzoate, CHClNO, (), in the space group with = 2. In the crystal of (), mol-ecules are linked by C-H⋯N hydrogen bonds, forming chains with (6) motifs parallel to the axis.

Crystal structure and Hirshfeld surface analysis of a new polymorph of ()-2-(4-bromo-phen-yl)-1-[2,2-di-bromo-1-(3-nitro-phen-yl)ethen-yl]diazene.

A new polymorph of the title compound, CHBrNO, (form-2) was obtained in the same manner as the previously reported form-1 [Akkurt (2022 ▸). E, 732-736]. The structure of the new polymorph is stabilized by a C-H⋯O hydrogen bond that links mol-ecules into chains.

Crystal structure and Hirshfeld surface analysis of ()-1-[2,2-di-bromo-1-(4-nitro-phen-yl)ethen-yl]-2-(4-fluoro-phen-yl)diazene.

In the title compound, CHBrFNO, the 4-fluoro-phenyl ring and the nitro-substituted phenyl ring form a dihedral angle of 64.37 (10)°. Mol-ecules in the crystal are connected by C-H⋯O and C-H⋯F hydrogen bonds into layers parallel to (011).