2-[(E)-2-(1H-Indol-3-yl)ethen-yl]-1-methyl-pyridinium 4-chloro-benzene-sulfonate.

In the title compound, C(16)H(15)N(2) (+)·C(6)H(4)ClO(3)S(-), the cation exists in an E configuration with respect to the central C=C bond and is approximately planar, with a dihedral angle of 2.95 (5)° between the pyridinium and indole rings. The mean plane of the π-conjugated system of the cation and the benzene ring of the anion are inclined to each other at a dihedral angle of 69.65 (4)°. In the crystal packing, the cations are stacked in an anti-parallel manner along the a axis, resulting in a π-π inter-action with a centroid-centroid distance of 3.5889 (7) Å. The anions are linked into a chain along the a axis by weak C-H⋯O inter-actions. The cations are linked with the anions into a three-dimensional network by N-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. There are also short O⋯Cl [3.1272 (10) Å] and C⋯O [3.1432 (14)-3.3753 (14) Å] contacts. The crystal structure is further stabilized by C-H⋯π inter-actions.