Crystal structures and Hirshfeld surface analyses of methyl 4-{2,2-di-chloro-1-[(E)-phenyl-diazen-yl]eth-enyl}benzoate, methyl 4-{2,2-di-chloro-1-[(E)-(4-methyl-phen-yl)diazen-yl]ethen-yl}benzoate and methyl 4-{2,2-di-chloro-1-[(E)-(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-[(E)-phenyl-diazen-yl]ethen-yl}benzoate, C16H12Cl2N2O2, (I), and methyl 4-{2,2-di-chloro-1-[(E)-(4-methyl-phen-yl)diazen-yl]ethen-yl}benzoate, C17H14Cl2N2O2, (II), crystallize in the space group P21/c with Z = 4, and methyl 4-{2,2-di-chloro-1-[(E)-(3,4-di-methyl-phen-yl)diazen-yl]ethen-yl}benzoate, C18H16Cl2N2O2, (III), in the space group P with Z = 2. In the crystal of (I), mol-ecules are linked by C-H⋯N hydrogen bonds, forming chains with C(6) motifs parallel to the b axis. Short inter-molecular Cl⋯O contacts of 2.8421 (16) Šand weak van der Waals inter-actions between these chains stabilize the crystal structure. In (II), mol-ecules are linked by C-H⋯O hydrogen bonds and C-Cl⋯π inter-actions, forming layers parallel to (010). Weak van der Waals inter-actions between these layers consolidate the mol-ecular packing. In (III), mol-ecules are linked by C-H⋯π and C-Cl⋯π inter-actions forming chains parallel to [011]. Furthermore, these chains are connected by C-Cl⋯π inter-actions parallel to the a axis, forming (01) layers. The stability of the mol-ecular packing is ensured by van der Waals forces between these layers.

Crystal structure and Hirshfeld surface analysis of a new polymorph of (E)-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, C14H8Br3N3O2, (form-2) was obtained in the same manner as the previously reported form-1 [Akkurt et al. (2022 ▸). Acta Cryst. E78, 732-736]. The structure of the new polymorph is stabilized by a C-H⋯O hydrogen bond that links mol-ecules into chains. These chains are linked by face-to-face π-π stacking inter-actions, resulting in a layered structure. Short inter-mol-ecular Br⋯O contacts and van der Waals inter-actions between the layers aid in the cohesion of the crystal packing. In the previously reported form-1, C-H⋯Br inter-actions connect mol-ecules into zigzag chains, which are linked by C-Br⋯π inter-actions into layers, whereas the van der Waals inter-actions between the layers stabilize the crystal packing of form-2. Hirshfeld mol-ecular surface analysis was used to compare the inter-molecular inter-actions of the polymorphs.

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

In the title compound, C14H8Br2FN3O2, 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). The crystal packing is consolidated by C-Br⋯π and C-F⋯π inter-actions, as well as by π-π stacking inter-actions. According to a Hirshfeld surface analysis of the crystal structure, the most significant contributions to the crystal packing are from O⋯H/H⋯O (15.0%), H⋯H (14.3%), Br⋯H/H⋯Br (14.2%), C⋯H/H⋯C (10.1%), F⋯H/H⋯F (7.9%), Br⋯Br (7.2%) and Br⋯C/C⋯Br (5.8%) contacts.