Crystal structure of tetra­methyl­ammonium 1,1,7,7-tetra­cyano­hepta-2,4,6-trienide

The title compound, C(4)H(12)N(+)·C(11)H(5)N(4) (−), contains one tetra­methyl­ammonium cation and one 1,1,7,7-tetra­cyano­hepta-2,4,6-trienide anion in the asymmetric unit. The anion is in an all-trans conjugated C=C bonds conformation. Two terminal C(CN)(2) di­nitrile moieties are slightly twisted from the polymethine main chain to which they are attached [C(CN)(2)/C(5) dihedral angles = 6.1 (2) and 7.1 (1)°]. The C—C bond distances along the hepta­dienyl chain vary in the narrow range 1.382 (2)–1.394 (2) Å, thus indicating the significant degree of conjugation. In the crystal, the anions are linked into zigzag chains along the [10[Image: see text]] direction by C—H⋯N(nitrile) short contacts. The anti­parallel chains stack along the [110] direction with alternating separations between the neighboring anions in stacks of 3.291 and 3.504 Å. The C—H⋯N short contacts and stacking inter­actions combine to link the anions into layers parallel to the ([Image: see text]01) plane and separated by columns of tetra­methyl­ammonium cations.