Crystal structure of (E)-1,2-bis(4-bromo-2,6-difluorophenyl)diazene

In the crystal, molecules of the centrosymmetric title compound, C12H4Br2F4N2, are linked into strands along [011] by weak C—H⋯F contacts. Furthermore, the molecules are π–π stacked with perpendicular ring distances of 3.4530 (9) Å.


Related literature
Hydrogen-bond geometry (Å , ). impact on binding affinities to its biological target. Therefore, a wide variety of transmembrane proteins, such as ionchannels [Banghart et al. (2004)] and metabotropic receptors [Levitz et al. (2013)], as well as enzymatic activity [Broichhagen et al. (2014)] and cell survival [Velema et al. (2013)] has been manipulated with azobenzene-based molecular structures. With our ongoing research in photopharmacology, we aimed to synthesize tetrafluoro-azobenzenes, which are characterized by their bistability once isomerized [Bléger et al. (2012)]. During our synthetic studies, we obtained (E)-1,2-bis(4-bromo-2,6-difluorophenyl)diazene (1) in a crystalline form, which we are reporting herein. This symmetric molecule serves as a precursor for further functionalization and implementation in photopharmacological studies, which will be described in a separate publication.

D-HÁ
The molecular structure of the title compound is depicted in Figure  The packing of the title compound is dominated by weak C-H···F contacts, Br-π contacts and π-stacking. Strands along [011] are formed by C-H···F contacts (see Figure 2 and Table 1 for details). The π-stacking is well visible in Figure 3.
The molecules are arranged staggered by what the azo group and the Br substituent of adjacent molecules are located above or below a phenyl ring. The centre of gravity of the phenyl ring (coordinates x = 0.28683, y = 0.5321, z = 0.56133) is in a distance of 3.412 and 3.459 Å from the N-atoms of the azo group (N1 ii with ii = x,1 + y,z and N1 iii with iii = 1 -x,2y,-z resp.) and 3.573 (1) Å from an adjacent Br substituent (Br1 iv with iv = x,-1 + y,z). The perpendicular distances of phenyl rings interacting by π-contacts are in a narrow range of 3.4528 (9) and 3.4532 (9) Å with a Cg-Cg distance of sup-2 Acta Cryst. (2015). E71, o459-o460 4.5665 (14) Å. Besides the π contact the Br substituent forms weak contacts to two adjacent Br substituents in a distance of 3.6817 (4) Å each (Br1 v and Br1 vi with v = -x,1/2 + y,1/2 -z and vi = -x,-1/2 + y,1/2 -z).

S3. Refinement
All H atoms were found in difference maps. C-bonded H atoms were positioned in ideal geometry (C-H = 0.95 Å) and treated as riding on their parent atoms [U iso (H) = 1.2U eq (C)].

Figure 1
The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 30% probability level) for non-H atoms. Symmetry code: (i) 1 -x, 2 -y, 1 -z.

Figure 3
The unit cell of the title compound (displacement ellipsoids drawn at 30% probability level).

(E)-1,2-bis(4-bromo-2,6-difluorophenyl)diazene
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on all data will be even larger.