1-Piperonylpiperazinium 4-nitro-benzoate monohydrate.

IN THE TITLE HYDRATED SALT [SYSTEMATIC NAME: 1-(1,3-benzodioxol-5-ylmeth-yl)piperazin-1-ium 4-nitro-benzoate monohydrate], C12H17N2O2 (+)·C7H4NO4 (-)·H2O, the piperazinium ring of the cation adopts a slightly distorted chair conformation. The piperonyl and piperazine rings are rotated with respect to each other with an N-C-C-C torsion angle of 45.6†(2)°. In the anion, the nitro group is almost coplanar with the adjacent benzene ring, forming a dihedral angle of only 3.9†(4)°. In the crystal, the cations, anions and water mol-ecules are linked through N-H⋯O and O-H⋯O hydrogen bonds into chains along the a axis. In addition, weaker inter-molecular C-H⋯O inter-actions are also observed within the chains. The anions form centrosymmetric couples through π-stacking inter-actions, with an inter-centroid distance of 3.681†(4)†à between the benzene rings.