Crystal structure of the 1:1 adduct of (E)-5-(2,3-di­hydro­benzo[d]thia­zol-2-yl­idene)-2,6-dioxo-4-phenyl-1,2,5,6-tetra­hydro­pyridine-3-carbo­nitrile and its piperidinium salt, piperidinium (Z)-5-(benzo[d]thia­zol-2-yl)-3-cyano-6-oxo-4-phenyl-1,6-di­hydro­pyridin-2-olate

The central pyridinic rings are approximately coplanar to the benzo­thia­zole moieties in both the neutral mol­ecule and the anion. Bond lengths and angles indicate considerable delocalization of the multiple bonding. The neutral mol­ecule is E-configured about the central C=C bond, but the anion is Z. Classical and ‘weak’ hydrogen bonds lead to a broad ribbon of residues.

In the structure of the title compound, C₅H₁₂N⁺·C₁₉H₁₀N₃O₂S⁻·C₁₉H₁₁N₃O₂S, the central pyridinic rings are approximately coplanar to the benzo­thia­zole moieties. The phenyl groups are appreciably angled to the central rings [inter­planar angles of 57.30 (3)° for the anion and 79.01 (4)° for the neutral mol­ecule]. Bond lengths and angles correspond to considerable delocalization of the π bonding, especially for the anion; all four C=O bond lengths are similar [1.2365 (13)–1.2591 (13) Å]. The two main residues display different configurations about the formally double C—C bonds between the benzo­thia­zole and pyridinic ring systems; the neutral mol­ecule is E, facilitating an intra­molecular N—H⋯O hydrogen bond, but the anion is Z, allowing a short intra­molecular S⋯O contact of 2.5794 (10) Å. Within the asymmetric unit, the piperidinium cation is hydrogen bonded to an oxygen atom of the anion; the anion and the neutral mol­ecule are connected by two N—H⋯O hydrogen bonds, forming a ring of graph-set R²₂(8). Asymmetric units are linked to form inversion-symmetric dimers by an H_cation⋯O_anion hydrogen bond. These are further linked by a C—H⋯O hydrogen bond to form a broad ribbon of residues parallel to the a axis.