Date Published: June 01, 2011
Publisher: International Union of Crystallography
Author(s): Dieter Schollmeyer, Heiner Detert.
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.
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 ▶).