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 (2Z)-N,N-dimethyl-2-(penta-fluoro-phen-yl)-2-(2-phenyl-hydrazin-1-yl-idene)acetamide.

In the title compound, C16H12F5N3O, the dihedral angle between the aromatic rings is 31.84 (8)°. In the crystal, the mol-ecules are linked into dimers possessing crystallographic twofold symmetry by pairwise N-H⋯O hydrogen bonds and weak C-H⋯O hydrogen bonds and aromatic π-π stacking inter-actions link the dimers into a three-dimensional network. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from F⋯H/H⋯F (41.1%), H⋯H (21.8%), C⋯H/H⋯C (9.7%) C⋯C (7.1%) and O⋯H/H⋯O (7.1%) contacts. The contribution of some disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] in PLATON. The solvent contribution was not included in the reported mol-ecular weight and density.