1-Piperonylpiperazinium 4-chlorobenzoate

In the title salt {systematic name: 1-[(1,3-benzodioxol-5-yl)methyl]piperazin-1-ium 4-chlorobenzoate}, C12H17N2O2 +·C7H4ClO2 −, the piperazine ring adopts a slightly disordered chair conformation. The dioxole ring is in a flattened envelope conformation with the methylene C atom forming the flap. The relative orientation of the piperonyl ring system and the piperazine rings is reflected in the N—C—C C torsion angle of 132.3 (1)°. In the anion, the mean plane of the carboxylate group is twisted from that of the benzene ring by 14.8 (9)°. In the crystal, the components are linked by N—H⋯O and weak C—H⋯O hydrogen bonds, forming chains along [010].

In the title salt {systematic name: 1-[(1,3-benzodioxol-5-yl)methyl]piperazin-1-ium 4-chlorobenzoate}, C 12 H 17 N 2 O 2 + Á-C 7 H 4 ClO 2 À , the piperazine ring adopts a slightly disordered chair conformation. The dioxole ring is in a flattened envelope conformation with the methylene C atom forming the flap. The relative orientation of the piperonyl ring system and the piperazine rings is reflected in the N-C-C . . . C torsion angle of 132.3 (1) . In the anion, the mean plane of the carboxylate group is twisted from that of the benzene ring by 14.8 (9) . In the crystal, the components are linked by N-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds, forming chains along [010].

Experimental
Piperazines are among the most important building blocks in today's drug discovery and are found in biologically active compounds across a number of different therapeutic areas (Brockunier et al., 2004;Bogatcheva et al., 2006). A review of the current pharmacological and toxicological information for piperazine derivatives is described (Elliott, 2011). The crystal structure of an N-piperonyl analogue of the atypical antipsychotic clozapine (Capuano et al., 2000) is reported. In continuation of our work on salts of piperonylpiperazines, this paper reports the crystal structure of the title compound (I).
The asymmetric unit of (I) consists of a 1-piperonylpiperazinium cation and a p-chlorobenzoate anion (Fig. 1). The piperazine ring in the cation adopts a slightly disordered chair conformation (puckering parameters Q, θ, and φ = 0.5761 (14) Å , 177.7 (2) ° and 177 (4) °; (Cremer & Pople, 1975). The dioxole group is in a slightly distorted envelope configuration (puckering parameters Q and φ = 0.1693 (15) Å and 36.1 (5) ° with atom C5A displaced by 0.2683 (18) Å from the plane through the other four atoms). The piperonyl ring system and the piperazine rings are twisted with respect to each other as reflected in the N1A-C1A-C2A-C8A torsion angle of 132.2 (5)°. In the anion, the mean plane of the carboxylate group is twisted from that of the benzene ring by 14.8 (9)°. Bond lengths are in normal ranges (Allen et al., 1987). In the crystal, N-H···O hydrogen bonds and a weak C10A-H10A···O2B iii intermolecular interactions are observed which influence the crystal packing stability forming 1-D chains along [0 1 0] (Fig. 2).

Experimental
1-piperonylpiperazine ( 2.2 g, 0.01 mol) and p-chlorobenzoic acid (1.56 g, 0.01 mol) were dissolved in hot N,N-dimethylformamide and stirred for 10 mins at 323 K. The resulting solution was allowed to cool slowly at room temperature. The crystals of the title salt appeared after a few days and were suitable for X-ray studies (m.p.:464-470 K).

Refinement
All H atoms were placed in calculated positions and then refined using the riding-model approximation with Atom-H lengths of 0.93Å (CH), 0.97Å (CH 2 ) or 0.90Å (NH). Isotropic displacement parameters were set to 1.2U eq of the parent atom.

Figure 1
The asymmetric unit of (I) with 30% probability displacement ellipsoids.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.