Crystal structure of the 1:1 co-crystal 4-(di-methylamino)-pyridin-1-ium 8-hy-droxy-quinoline-5-sulfonate- N , N -di-methyl-pyridin-4-amine.

The asymmetric unit of the title compound is composed of two independent ion pairs of 4-(di-methyl-amino)-pyridin-1-ium 8-hy-droxy-quinoline-5-sulfonate (HDMAP + ·HqSA - , C 7 H 11 N 2 + ·C 9 H 6 NO 4 S - ) and neutral N , N -di-methyl-pyridin-4-amine mol-ecules (DMAP, C 7 H 10 N 2 ), co-crystallized as a 1:1:1 HDMAP + :HqSA - :DMAP adduct in the monoclinic system, space group Pc . The compound has a layered structure, including cation layers of HDMAP + with DMAP and anion layers of HqSA - in the crystal. In the cation layer, there are inter-molecular N-H⋯N hydrogen bonds between the protonated HDMAP + mol-ecule and the neutral DMAP mol-ecule. In the anion layer, each HqSA - is surrounded by other six HqSA - , where the planar network structure is formed by inter-molecular O-H⋯O and C-H⋯O hydrogen bonds. The cation and anion layers are linked by inter-molecular C-H⋯O hydrogen bonds and C-H⋯ π inter-actions.