Dioxopromethazinium picrate

The title compound {systematic name: [1-(9,9-dioxo-10H-phenothiazin-10-yl)-2-propyl] dimethylammonium 2,4,6-trinitrophenolate}, C17H21N2O2S+ center dot C6H2N3O7-, is a molecular salt arising from the reaction of racemic dioxopromethazine and picric acid, crystallizing with three ion pairs in the asymmetric unit. The conformations of the three distinct cations are very similar and each associates with a nearby picrate anion by way of hydrogen bonds. In one case, a simple N-H center dot center dot center dot O link occurs to the acceptor deprotonated phenol O atom; the other two ion pairs are linked by bifurcated N-H center dot center dot center dot(O,O) hydrogen bonds, where the second O atom is part of a nitro group. In the crystal structure, there is weak pi-pi stacking involving two of the picrate aromatic rings [ring-centroid separation = 3.676 (2) angstrom].