6-(4-Aminophenyl)-4-(4-ethoxyphenyl)-2-methoxynicotinonitrile

In the title molecule, C21H19N3O2, the central pyridine ring makes dihedral angles of 14.46 (9) and 34.67 (8)° with the 4-amino- and 4-ethoxy-substituted benzene rings, respectively. The ethoxy group is essentially coplanar with the attached benzene ring [C—O—C—C torsion angle = 178.70 (16)°] as is the methoxy group with the pyridine ring [C—O—C—N torsion angle = −3.0 (3)°]. In the crystal, molecules are linked by N—H⋯N hydrogen bonds into chains along [201]. Weak C—H⋯O hydrogen bonds and C—H⋯π interactions are also present.


Related literature
The title nicotinonitrile derivative is a cyclized product of a chalcone and a malononitrile in the present of sodium methoxide. For the synthesis and applications of substituted pyridines and nicotinonitrile derivatives, see: Al-Jaber et al.  Zhou et al. (2006). For a related structure, see: Chantrapromma et al. (2010). For standard bond-length data, see: Allen et al. (1987). H atoms treated by a mixture of independent and constrained refinement Á max = 0.19 e Å À3 Á min = À0.17 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).
It was found that (I) exhibits fluorescence with the maximum emission at 498 nm when was excited at 370 nm in DMSO.

Experimental
The title compound (I) was synthesized by stirring the solution of (E)-1-(4-aminophenyl)-3-(4-ethoxyphenyl)prop-2en-1-one (0.27 g, 1 mmol) in methanol (10 ml) with a freshly prepared sodium methoxide (1.0 mmol of sodium in 20 ml of methanol). Excess malononitrile (0.13 g, 2.0 mmol) was then added with continuous stirring at room temperature until the precipitate was separated out. The resulting solid was filtered. Pale brown block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from methanol/ethanol (1:1 v/v) by the slow evaporation of the solvent at room temperature over several days, Mp. 477-478 K.

Refinement
Amino H atoms were located in difference maps and refined isotropically. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic, 0.97 for CH 2 and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.

Figure 2
The crystal packing of the title compound viewed along the a axis. Hydrogen bonds are shown as dashed lines. 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 > σ(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.