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.

Structural Organization of Dibromodiazadienes in the Crystal and Identification of Br···O Halogen Bonding Involving the Nitro Group.

Nitro functionalized dibromodiazadiene dyes were prepared and fully characterized including X-ray single crystal analysis. Electron deficient dibromodiazadienes were found to be able to act as donors of halogen bonding (XB), while the nitro group acted as an acceptor of the XB. Depending on the substituents, the Br···O XB competed with other weak interactions, and for some of the dyes, they even outcompeted the XB involving the nitro group. However, the nitro functionalized dibromoalkenes 6a and 10a, which had only the nitro moiety as the most plausible acceptor of the XB, reliably formed 1D chains via Br⋯O XB. Experimental work was supported by the DFT calculations and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method).

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

The mol-ecule of the title compound, C14H8Br3N3O2, consists of three almost planar groups: the central di-bromo-ethenyldiazene fragment and two attached aromatic rings. The mean planes of these rings form dihedral angles with the plane of the central fragment of 26.35 (15) and 72.57 (14)° for bromine- and nitro-substituted rings, respectively. In the crystal, C-H⋯Br inter-actions connect mol-ecules, generating zigzag C(8) chains along the [100] direction. These chains are linked by C-Br⋯π inter-actions into layers parallel to (001). van der Waals inter-actions between the layers aid in the cohesion of the crystal packing. The most substantial contributions to crystal packing, according to a Hirshfeld surface analysis, are from Br⋯H/H⋯Br (20.9%), C⋯H/H⋯C (15.2%), O⋯H/H⋯O (12.6%) and H⋯H (11.7%) contacts.

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.

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

In the title compound, C14H8Br2FN3O2, the nitro-substituted benzene ring and the 4-fluoro-phenyl ring form a dihedral angle of 65.73 (7)°. In the crystal, mol-ecules are linked into chains by C-H⋯O hydrogen bonds running parallel to the c-axis direction. The crystal packing is consolidated by C-F⋯π inter-actions and π-π stacking inter-actions, and short Br⋯O [2.9828 (13) Å] contacts are observed. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (17.4%), O⋯H/H⋯O (16.3%), Br⋯H/H⋯Br (15.5%), Br⋯C/C⋯Br (10.1%) and F⋯H/H⋯F (8.1%) contacts.