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.