Crystal structure of 2,6-distyrylpyridine

We have crystallized the 2,6-distyrylpyridine compound from the condensation reaction of the 2,6-dimethylpyridine with benzaldehyde (at 135°C) to obtain a model compound having three rings joined with two double bonds in order to understand the structure of poly(2,6-styrylpyridine) and poly(2,6-pyridinediylvinylene) and their formation mechanism. The X-ray structure shows that the title compound belongs to the trigonal crystal system, space group P3², and with unit cell dimensions a = 15.5637 (12) Å, c = 5.7852 (13) Å. From the molecular structure it was clear that the substituents on double bonds were in the trans position, which was in agreement to the IR and ¹H NMR results. The molecule is planar and forms stacks in the crystal. The molecular structure of 2,6-distyrylpyridine has two trans double bonds between the rings and therefore it can be in three nonequivalent conformations. The preferred conformation showed by X-ray crystallography can be the result of weak steric interactions between the double bond trans hydrogens and the nearby hydrogens of the phenyl or pyridyl groups. The crystal structure, and IR and ¹H NMR results are currently reported.