Monoclinic polymorph of 2,5-bis[4-(dimethylamino)styryl]-3,6-dimethylpyrazine

Abstract

The title compound, C26H30N4, was prepared by condensation of tetramethylpyrazine and dimethylaminobenzaldehyde and crystallizes from chloroform/methanol in two different forms. Block-shaped crystals belong to the monoclinic crystal system and plates to the triclinic system. The two crystal forms differ in the arrangement of the centrosymmetric molecules, which have nearly identical geometries. In the monoclinic crystals reported here, planar molecules [maximum deviation = 0.062 (2) Å], with a transoid arrangement of the (E)-styryl units and completely planarized dimethylamino groups [sum of the C—N bond angles = 359.9 (2)°], form layers connected via H–π-stacking. The dihedral angle between the central and pendant rings is 1.30 (8)°. The triclinic polymorph contains two half molecules, both completed by crystallographic inversion symmetry.