Halogenated Diazabutadiene Dyes: Synthesis, Structures, Supramolecular Features, and Theoretical Studies.

Novel halogenated aromatic dichlorodiazadienes were prepared via copper-mediated oxidative coupling between the corresponding hydrazones and CCl4. These rare azo-dyes were characterized using 1H and 13C NMR techniques and X-ray diffraction analysis for five halogenated dichlorodiazadienes. Multiple non-covalent halogen···halogen interactions were detected in the solid state and studied by DFT calculations and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method). Theoretical studies demonstrated that non-covalent halogen···halogen interactions play crucial role in self-assembly of highly polarizable dichlorodiazadienes. Thus, halogen bonding can dictate a packing preference in the solid state for this class of dichloro-substituted heterodienes, which could be a convenient tool for a fine tuning of the properties of this novel class of dyes.

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.

Crystal structure and Hirshfeld surface analysis of (E)-4-({2,2-di-chloro-1-[4-(di-methyl-amino)-phen-yl]ethenyl}diazen-yl)benzo-nitrile.

In the title compound, C17H14Cl2N4, the dihedral angle between the aromatic rings is 50.09 (9)°. The central -N=N- unit shows an E configuration. In the crystal, C-H⋯N inter-actions, C-Cl⋯π and π-π stacking inter-actions [centroid-to-centroid distance = 3.7719 (14) Å] link the mol-ecules, forming mol-ecular layers approximately parallel to the (002) plane. Additional weak van der Waals inter-actions between the layers consolidate the three-dimensional packing. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (33.6%), N⋯H/ H⋯N (17.2%), Cl⋯H/H⋯Cl (14.1%) and C⋯H/H⋯C (14.1%) contacts.

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

In the title compound, C14H7Cl4FN2, the dihedral angle between the 4-fluoro-phenyl ring and the 2,4-di-chloro-phenyl ring is 46.03 (19)°. In the crystal, the mol-ecules are linked by C-H⋯N inter-actions along the a-axis direction, forming a C(6) chain. The mol-ecules are further connected by C-Cl⋯π inter-actions and face-to-face π-π stacking inter-actions, forming ribbons along the a-axis direction. Hirshfeld surface analysis indicates that the greatest contributions to the crystal packing are from Cl⋯H/H⋯Cl (35.1%), H⋯H (10.6%), C⋯C (9.7%), Cl⋯Cl (9.4%) and C⋯H/H⋯C (9.2%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-4-{2,2-di-chloro-1-[(3,5-di-methyl-phen-yl)diazen-yl]ethen-yl}-N,N-di-methyl-aniline.

In the title compound, C18H19Cl2N3, the planes of the benzene rings subtend a dihedral angle of 77.07 (10)°. In the crystal, mol-ecules are associated into inversion dimers via short Cl⋯Cl contacts [3.3763 (9) Å]. A Hirshfeld surface analysis indicates that the most important contact percentages for the different types of inter-actions are H⋯H (43.9%), Cl⋯H/H⋯Cl (22.9%), C⋯H/H⋯C (20.8%) and N⋯H/H⋯N (8.0%).

(E)-1-(2,6-Di-chloro-phen-yl)-2-(3-nitro-benzyl-idene)hydrazine: crystal structure and Hirshfeld surface analysis.

The stabilized conformation of the title compound, C13H9Cl2N3O2, is similar to that of the isomeric compound (E)-1-(2,6-di-chloro-phen-yl)-2-(2-nitro-benzyl-idene)hydrazine. The 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 26.25 (16)°. In the crystal, face-to-face π-π stacking inter-actions along the a-axis direction occur between the centroids of the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring. The mol-ecules are further linked by C-H⋯O contacts and N-H⋯O and C-H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded mol-ecular layers parallel to (100). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (22.1%), Cl⋯H/H⋯Cl (20.5%), O⋯H/H⋯O (19.7%), C⋯C (11.1%) and C⋯H/H⋯C (8.3%) inter-actions.

Crystal structure and Hirshfeld surface analysis of 4-{2,2-di-chloro-1-[(E)-(4-chloro-phen-yl)diazen-yl]ethen-yl}-N,N-di-methyl-aniline.

The title compound, C16H14Cl3N3, comprises three mol-ecules of similar shape in the asymmetric unit. The crystal cohesion is ensured by inter-molecular C-H⋯N and C-H⋯Cl hydrogen bonds in addition to C-Cl⋯π inter-actions. Hirshfeld surface analysis and two-dimensional fingerprint plots reveal that Cl⋯H/H⋯Cl (33.6%), H⋯H (27.9%) and C⋯H/H⋯C (17.6%) are the most important contributors towards the crystal packing.

Crystal structure and Hirshfeld surface analysis of 4-{2,2-di-chloro-1-[(E)-2-(4-methyl-phen-yl)diazen-1-yl]ethen-yl}-N,N-di-methyl-aniline.

In the tile compound, C17H17Cl2N3, the dihedral angle between the benzene rings is 62.73 (9)°. In the crystal, there are no classical hydrogen bonds. Mol-ecules are linked by a pair of C-Cl⋯π inter-actions, forming an inversion dimer. A short inter-molecular HL⋯HL contact [Cl⋯Cl = 3.2555 (9) Å] links the dimers, forming a ribbon along the c-axis direction. The Hirshfeld surface analysis and two-dimensional fingerprint plots reveal that the most important contributions for the crystal packing are from H⋯H (45.4%), Cl⋯H/H⋯Cl (21.0%) and C⋯H/H⋯C (19.0%) contacts.

Crystal structure and Hirshfeld surface analysis of 4-{2,2-di-chloro-1-[(E)-(4-fluoro-phen-yl)diazen-yl]ethen-yl}-N,N-di-methyl-aniline.

In the title compound, C16H14Cl2FN3, the dihedral angle between the two aromatic rings is 64.12 (14)°. The crystal structure is stabilized by a short Cl⋯H contact, C-Cl⋯π and van der Waals inter-actions. The Hirshfeld surface analysis and two-dimensional fingerprint plots show that H⋯H (33.3%), Cl⋯H/H⋯Cl (22.9%) and C⋯H/H⋯C (15.5%) inter-actions are the most important contributors towards the crystal packing.

Crystal structure and Hirshfeld surface analysis of (E)-1-(2,6-di-chloro-phen-yl)-2-(2-nitro-benzyl-idene)hydrazine.

In the title compound, C13H9Cl2N3O2, the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 21.16 (14)°. In the crystal, face-to-face π-π stacking inter-actions occur along the a-axis direction between the centroids of the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring. Furthermore, these mol-ecules show intra-molecular N-H⋯Cl and C-H⋯O contacts and are linked by inter-molecular N-H⋯O and C-H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded mol-ecular layers parallel to (20). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (23.0%), O⋯H/H⋯O (20.1%), Cl⋯H/H⋯Cl (19.0%), C⋯C (11.2%) and H⋯C/C⋯H (8.0%) inter-actions.

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

In the title compound, C14H8Cl2FN3O2, the 4-fluoro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 63.29 (8)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into chains running parallel to the c axis. The crystal packing is further stabilized by C-Cl⋯π, C-F⋯π and N-O⋯π inter-actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯O/O⋯H (15.5%), H⋯H (15.3%), Cl⋯H/H⋯Cl (13.8%), C⋯H/H⋯C (9.5%) and F⋯H/H⋯F (8.2%) inter-actions.

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

In the title compound, C14H8Cl3FN2, the planes of the 4-fluoro-phenyl ring and the 4-chloro-phenyl ring make a dihedral angle of 56.13 (13)°. In the crystal, mol-ecules are stacked in a column along the a axis via a weak C-H⋯Cl hydrogen bond and face-to-face π-π stacking inter-actions [centroid-centroid distances = 3.8615 (18) and 3.8619 (18) Å]. The crystal packing is further stabilized by short Cl⋯Cl contacts. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from Cl⋯H/H⋯Cl (31.2%), H⋯H (14.8%), C⋯H/H⋯C (14.0%), F⋯H/H⋯F (12.8%), C⋯C (9.0%) and Cl⋯Cl (6.7%) inter-actions.

Crystal structures and Hirshfeld surface analyses of the two isotypic compounds (E)-1-(4-bromo-phen-yl)-2-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]diazene and (E)-1-(4-chloro-phen-yl)-2-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]diazene.

In the two isotypic title compounds, C14H8BrCl2N3O2, (I), and C14H8Cl3N3O2, (II), the substitution of one of the phenyl rings is different [Br for (I) and Cl for (II)]. Aromatic rings form dihedral angles of 60.9 (2) and 64.1 (2)°, respectively. Mol-ecules are linked through weak X⋯Cl contacts [X = Br for (I) and Cl for (II)], C-H⋯Cl and C-Cl⋯π inter-actions into sheets parallel to the ab plane. Additional van der Waals inter-actions consolidate the three-dimensional packing. Hirshfeld surface analysis of the crystal structures indicates that the most important contributions for the crystal packing for (I) are from C⋯H/H⋯C (16.1%), O⋯H/H⋯O (13.1%), Cl⋯H/H⋯Cl (12.7%), H⋯H (11.4%), Br⋯H/H⋯Br (8.9%), N⋯H/H⋯N (6.9%) and Cl⋯C/C⋯Cl (6.6%) inter-actions, and for (II), from Cl⋯H / H⋯Cl (21.9%), C⋯H/H⋯C (15.3%), O⋯H/H⋯O (13.4%), H⋯H (11.5%), Cl⋯C/C⋯Cl (8.3%), N⋯H/H⋯N (7.0%) and Cl⋯Cl (5.9%) inter-actions. The crystal of (I) studied was refined as an inversion twin, the ratio of components being 0.9917 (12):0.0083 (12).