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

The title compound, C(26)H(30)N(4), 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.