N,N-Dihexyl-4-[2-(4-nitro­phen­yl)vin­yl]aniline

Dieter Schollmeyer; Heiner Detert

doi:10.1107/S1600536811016709

. 2011 May 11;67(Pt 6):o1384–o1385. doi: 10.1107/S1600536811016709

N,N-Dihexyl-4-[2-(4-nitrophenyl)vinyl]aniline

Dieter Schollmeyer ^a, Heiner Detert ^a,^*

PMCID: PMC3120587 PMID: 21754774

Abstract

The title compound, C₂₆H₃₆N₂O₂, was prepared by Horner olefination of p-dihexylaminobenzaldehyde and diethyl p-nitrobenzylphosphonate. It crystallizes with two independent molecules in the asymmetric unit. Both have similar geometries of the π-systems but the conformations of all hexyl chains are different. Whereas one hexyl chain of the first molecule shows the typical all-anti conformation, the second is arranged in a gauche-anti-gauche-anti conformation with N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles of −65.1 (4), 167.3 (3), 63.3 (4), and 179.4 (3)°. One of the hexyl chains in the other molecule has an anti-anti-gauche-anti conformation [N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles = 179.6 (3), −179.8 (3), −68.7 (5) and −178.8 (4)°], the other starts with an anti-gauche-gauche sequence. Molecules A and B are composed of five planar subunits. The angle sums around the N atoms are in the range 356 (2)–360.0 (2)°. Torsion angles between these segments do not exceed 4.9 (4)°, except for one of the alkyl chains each [molecule A = 26.2 (4)°; molecule B = −6.0 (4)°]. The high planarity of the molecules and the short aniline C—N bonds [1.385 (3) Å in molecule A and 1.378 (3) Å in molecule B] indicate a strong electronic coupling through the stilbene unit. One methylene group is disordered over two positions with an occupancy ratio of 0.72:0.28.

Related literature

For chromophores and fluorophores based on quadrupolar donor–acceptor-substituted stilbenoid systems, see: Detert & Sugiono (2005 ▶); Strehmel et al. (2003 ▶); Nemkovich et al. (2010 ▶). Similar aminonitrostilbenes had been prepared earlier, see: Pfeiffer et al. (1915 ▶); Chardonnens & Heinrich (1939 ▶); Meier et al. (2004 ▶). The optical properties of these dyes are strongly dependent on charge transfer and torsion angles, see: Baumann et al. (1977 ▶); Goerner (1998 ▶); Dekhtyar & Rettig (2007 ▶). Conjugated oligomers with basic sites are sensing materials for polarity and cations, see: Wilson & Bunz (2005 ▶); Zucchero et al. (2009 ▶). For a comparable compound, see: Fischer et al. (2011 ▶).

Experimental

Crystal data

C₂₆H₃₆N₂O₂
M _r = 408.57
Triclinic,
a = 9.6574 (9) Å
b = 11.4153 (10) Å
c = 23.604 (2) Å
α = 93.297 (3)°
β = 94.834 (3)°
γ = 112.696 (3)°
V = 2380.6 (4) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 173 K
0.54 × 0.37 × 0.06 mm

Data collection

Bruker SMART APEXII diffractometer
Absorption correction: multi-scan (PLATON; Spek, 2009 ▶) T _min = 0.936, T _max = 0.996
90478 measured reflections
11464 independent reflections
7228 reflections with I > 2σ(I)
R _int = 0.062

Refinement

R[F ² > 2σ(F ²)] = 0.082
wR(F ²) = 0.239
S = 1.02
11464 reflections
553 parameters
H-atom parameters constrained
Δρ_max = 0.76 e Å⁻³
Δρ_min = −0.46 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: SAINT (Bruker, 2006 ▶); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811016709/bt5539sup1.cif

e-67-o1384-sup1.cif^{(38.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811016709/bt5539Isup2.hkl

e-67-o1384-Isup2.hkl^{(560.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811016709/bt5539Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

Financial support from the Deutsche Forschungsgemeinschaft is gratefully acknowledged.

supplementary crystallographic information

Comment

The title compound was prepared as a reference compound in a project focusing on chromophores and fluorophores based on quadrupolar donor-acceptor substituted stilbenoid systems, see: Detert & Sugiono (2005); Strehmel et al. (2003); and Nemkovich et al. (2010). Crystals of the title compound are composed of two independent molecules A and B with nearly identical geometries of the π-systems but different conformations of the alkyl chains. Whereas one hexyl chain of A shows the typical all-anti conformation, the second is arranged in a gauche-anti-gauche-anti conformation with torsion angles -65.1 (4)°, 167.3 (3)°, 63.3 (4)°, and 179.4 (3)°. The hexyl chains in B are also different, one has an anti-anti-gauche-anti conformation (torsion angles: 179.6 (3)°, -179.8 (3)°, -68.7 (5)°, and -178.8 (4)°), the other starts with an anti-gauche-gauche sequence and the penultimate C20B is disordered. The strong acceptor effect of the nitro groups through the stilbene unit is reflected by short aniline C—N-bonds: 1.385 (3)Å for C12A—N15A and 1.378 (3)Å for C12B—N15B and planar amino groups with angle sums on the aniline-N of 356° (A) and 359.7° (B). Accordingly, the stilbene framework is nearly coplanar with torsion angles of 2.7 (4)° for C7A—C8A—C9A—C10A (178.8 (2)°in B), -178.2 (2)° for C1A—C7A—C8A—C9A (179.3 (2)°in B), and -3.0 (4)° for C6A—C1A—C7A—C8A (175.9 (2)° in B). These bond lengths and torsion angles are similar to those reported for a 2,5-bis(dimethylaminostyryl)pyrazine (Fischer et al., 2011). The packing of the molecules in the crystal is dominated by the voluminous side chains. Parallel but alternatingly twisted nitrostilbenes form a herringbone lattice, perpendicular to this layer, the orientation of the neighbouring molecules is antiparallel.

Experimental

The title compound was prepared by adding potassium tert-butylate (1.46 g, 13 mmol) under nitrogen to a cooled solution of p-N,N-dihexylaminobenzaldehyde (2.17 g, 10 mmol) and diethyl p-nitrobenzylphosphonate (2.83 g, 10 mmol) in THF (anhyd., 50 ml) and the mixture was stirred for 2 h at 273 K and for further 2 h at ambient temperature. Acetic acid (2M, 5 ml) and water (70 ml) were added, the mixture was extracted with toluene (3 x 20 ml) and the pooled organic solutions were washed with brine (3 x 20 ml), dried (CaCl₂), concentrated in vacuo and the title compound was isolated from the red oil by chromatography on silica gel using toluene. Red crystals with m.p. = 351 K were obtained by slow evaporation of a solution of the title compound in methanol/chloroform.