Redetermination of 4-nitrostilbene

In the title compound, C14H11NO2, the benzene rings are inclined to each other with a dihedral angle between their mean planes of 8.42 (6)°. The nitro group is almost coplanar with the attached benzene ring but is rotated about the C—N bond by 5.84 (12)°. This redetermination results in a crystal structure with significantly higher precision than the original determination [Hertel & Romer (1931 ▶). Z. Kristallogr. 76, 467–469], and the intermolecular interactions have been established. In the crystal structure, molecules are linked by C—H⋯O hydrogen bonds to generate C(5), C(13) and edge-fused R 3 3(28) rings.

In the title compound, C 14 H 11 NO 2 , the benzene rings are inclined to each other with a dihedral angle between their mean planes of 8.42 (6) . The nitro group is almost coplanar with the attached benzene ring but is rotated about the C-N bond by 5. 84 (12) . This redetermination results in a crystal structure with significantly higher precision than the original determination [Hertel & Romer (1931). Z. Kristallogr. 76,[467][468][469], and the intermolecular interactions have been established. In the crystal structure, molecules are linked by C-HÁ Á ÁO hydrogen bonds to generate C(5), C(13) and edgefused R 3 3 (28) rings.

Comment
A great interest in the design of materials with potential applications in photonic technology has been developed in recent years (Luo et al., 2003;Vidal et al., 2008). Significant efforts have been focused on studying of design and the synthesis of organic molecules with potential nonlinear optical response (NLO), improved optical transparency and thermal stability (Park et al., 2004). A specific type of these molecules consists of electron donor and acceptor end groups interacting through a conjugating segment. In a first stage of work in our group, the synthesis of a stilbene molecule with nitro group with electron-withdrawing capacity as a substituent in para position, is considered. In order to obtain detailed structural information on the molecular conformation, its NLO responses, its hydrogen bonded interactions and its supramolecular arrangement, the crystal structure of p-nitrostilbene (I) was undertaken.
Perspective view of the title molecule, showing the atomic numbering scheme, is given in Fig. 1. The benzene rings are twisted out of the ethylene plane, as defined by the torsion angles C3-C4-C7-C8 and C7-C8-C9-C14 therefore the benzene rings are inclined to each other showing a dihedral angle between their mean planes of 8.42 (6)°. The nitro group is almost coplanar with the benzene ring but it is rotated about the C-N bond with an angle of rotation of 5.84 (12)°.
If compared with the C7-C8 bond length to the expected value for a localized double bond [1.317 (13) Å, Allen et al., 1987], the title distance shows some lengthening that is indicative of some π conjugation of the two benzene rings through the central ethene bridge. The torsion angle between the benzene rings [C4-C7═C8-C9 = 178.48 (12)°] indicates a trans geometry between them. The crystal structure of (I) is stabilized by weak C-H···O hydrogen-bonding interactions [Nardelli, 1995, Table 1]. The formation of the framework can be explained in terms of three-one substructures. In the first substructure atom C2 in the molecule at (x, y, z) acts as a hydrogen bond donor to nitro atom O1 in the molecule at (-1/2 + x, 1/2 -y, 2 -z) so generating, by 2 1 screw axes, C(5) chains which are running along [100] (Fig. 2). In the second substructure, atom C12 in the molecule at (x, y, z) acts as hydrogen bond donor to nitro atom O2 in the molecule at (x, 1/2 -y, -1/2 + z) so generating C(13) chains along [001] (Fig. 3). In the third-one dimensional substructure atom C12 in the molecule at (x, y, z) acts simultaneously as hydrogen bond donor to atoms O1 in the molecule at (x, 1/2 -y, -1/2 + z) and atom O1 in the molecule at (3/2 -x, -y, -1/2 + z) so generating a chain of edge-fused with graph motif R 3 3 (28) rings along [001] (Etter, 1990), [Fig. 4].

Experimental
The synthesis of (I) was prepared by taking equimolar quantities of benzyltriphenylphosphonium bromide (0.9600 g, 2.20 mmol) and 4-nitrobenzaldehyde (0.3355 g, 2.20 mmol). The mixture was stirred and it was taken to reflux in dry THF in a nitrogen atmosphere at 273 K. 3.3 mmol of potassium tert-butoxide was dissolved in 5 ml of t-butanol and this solution was added drop to drop to the phosphonium mixture obtaining a change in the color of the reaction mixture and completion of the reaction after two hours. Single crystals suitable for X-ray analysis were obtained by evaporation at room temperature using ethyl acetate as solvent.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance mat-  (18)