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

Johannes Broichhagen; David H Woodmansee; Dirk Trauner; Peter Mayer

doi:10.1107/S2056989015010622

. 2015 Jun 10;71(Pt 7):o459–o460. doi: 10.1107/S2056989015010622

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

Johannes Broichhagen ^a, David H Woodmansee ^a, Dirk Trauner ^a, Peter Mayer ^a,^*

PMCID: PMC4518941 PMID: 26279907

Abstract

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.

Keywords: crystal structure

Related literature

For background on azobenzenes, see: Mitscherlich (1834 ▸); Fehrentz et al. (2011 ▸); Banghart et al. (2004 ▸); Levitz et al. (2013 ▸); Broichhagen et al. (2014 ▸); Velema et al. (2013 ▸); Bléger et al. (2012 ▸). For the synthesis, see: Bléger et al. (2012 ▸). For related structures, see: Wragg et al. (2011 ▸); Gabe et al. (1981 ▸); Crispini et al. (1998 ▸); Elder & Vargas-Baca (2012 ▸); Komeyama et al. (1973 ▸); Ferguson et al. (1998 ▸); Reichenbächer et al. (2007 ▸). graphic file with name e-71-0o459-scheme1.jpg

Experimental

Crystal data

C₁₂H₄Br₂F₄N₂
M _r = 411.98
Monoclinic,
a = 10.3274 (5) Å
b = 4.5667 (2) Å
c = 13.1039 (6) Å
β = 90.340 (3)°
V = 618.00 (5) Å³
Z = 2
Mo Kα radiation
μ = 6.60 mm⁻¹
T = 173 K
0.14 × 0.07 × 0.02 mm

Data collection

Bruker D8 Quest diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2012 ▸) T _min = 0.572, T _max = 0.746
9803 measured reflections
1523 independent reflections
1218 reflections with I > 2σ(I)
R _int = 0.051

Refinement

R[F ² > 2σ(F ²)] = 0.027
wR(F ²) = 0.055
S = 1.02
1523 reflections
91 parameters
H-atom parameters constrained
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Data collection: Bruker Instrument Service (Bruker, 2007 ▸); cell refinement: APEX2 (Bruker, 2007 ▸); data reduction: SAINT (Bruker, 2007 ▸); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▸); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015 ▸); molecular graphics: ORTEP-III (Burnett & Johnson, 1996 ▸); software used to prepare material for publication: PLATON (Spek, 2009 ▸).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989015010622/nr2060sup1.cif

e-71-0o459-sup1.cif^{(332.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015010622/nr2060Isup2.hkl

e-71-0o459-Isup2.hkl^{(123KB, hkl)}

Click here for additional data file.^{(4.5KB, cml)}

Supporting information file. DOI: 10.1107/S2056989015010622/nr2060Isup3.cml

Click here for additional data file.^{(999.9KB, tif)}

x y z . DOI: 10.1107/S2056989015010622/nr2060fig1.tif

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.

Click here for additional data file.^{(1.1MB, tif)}

. DOI: 10.1107/S2056989015010622/nr2060fig2.tif

Weak C—H⋯F contacts (dotted lines) linking the title compound into strands along [011].

Click here for additional data file.^{(1.4MB, tif)}

. DOI: 10.1107/S2056989015010622/nr2060fig3.tif

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

CCDC reference: 1404445

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
C5H5F2ⁱ	0.95	2.53	3.190(3)	126

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank Professor Wolfgang Schnick for generous allocation of diffractometer time.

supplementary crystallographic information

S1. Comment

Azobenzenes, first discovered in 1834 [Mitscherlich (1834)], are experiencing a renaissance in the last decade for the photocontrol of biological function [Fehrentz et al. (2011)]. They offer cis-/trans-isomerism upon irradiation with discrete and orthogonal wavelengths of light. When attached to a pharmacophore, this conformational change has an impact on binding affinities to its biological target. Therefore, a wide variety of transmembrane proteins, such as ion-channels [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.

The molecular structure of the title compound is depicted in Figure 1. There are several structures containing (E)-1,2-bis(phenyl)diazene derivatives with at least one halogen substituent in 2-, 4- or 6-position reported in the literature, e.g. Wragg et al. (2011), Gabe et al. (1981), Crispini et al. (1998), Elder & Vargas-Baca (2012) and Komeyama et al. (1973). Furthermore there are two structures reported which contain the 4-bromo-2,6-difluorophenyl moiety [Ferguson et al. (1998), Reichenbächer et al. (2007)]. Due to centrosymmetry the phenyl rings are exactly coplanar, however, the entire molecule deviates significantly from exact planarity. The bond of the azo group forms an angle of 4.04 (16)° with the least-square plane of the phenyl ring while it is much larger with 13.21 (12)° in a related structure [Crispini et al. (1998)]. The C4–Br1 bond encloses an angle of 2.95 (10)° with the least-square plane of the phenyl ring which is quite close to the angle of 0.2 (3)° in a reported 4-bromo-2,6-difluorophenyl derivative [Ferguson et al. (1998)]. The 4-bromo-2,6-difluorophenyl derivative reported of Reichenbächer et al. (2007) is suitable for the comparison of bond lengths with the title compound since both compounds have been investigated at 173 K. In the title compound, the C–Br bond distance is 1.888 (2) Å which is almost in the same range of distances found in the reported structure: 1.889 (5), 1.883 (6) and 1.882 (6) Å. The C–F distances are 1.345 (3) and 1.335 (3) Å in the title compound and in the range of 1.336 (7) to 1.353 (7) Å in the related derivative [Reichenbächer et al. (2007)].

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 (N1ⁱⁱ with ⁱⁱ = x,1 + y,z and N1ⁱⁱⁱ with ⁱⁱⁱ = 1 - x,2 - y,-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 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).

S2. Experimental

(E)-1,2-bis(4-bromo-2,6-difluorophenyl)diazene (1) was synthesized as reported before and the spectral data matched the previously reported data [Bléger et al. (2012)]. Crystals suitable for X-Ray diffractometry were obtained as deep-red needles by slow evaporization from chloroform.