Cinnarizinium picrate

In the title salt {systematic name: 4-diphenylmethyl-1-[(E)-3-phenylprop-2-en-1-yl]piperazin-1-ium 2,4,6-trinitrophenolate), C26H29N2 +·C6H2N3O7 −, the cinnarizinium cation is protonated at the piperazine N atom connected to the styrenylmethyl group; the piperazine ring adopts a distorted chair conformaiton. In the crystal, bifurcated N—H⋯(O,O) hydrogen bonds link the components into two-ion aggregates.


Cinnarizinium picrate
Yanxi Song, C. S. Chidan Kumar, G. B. Nethravathi, S. Naveen and Hongqi Li Comment Cinnarizine (Stugeron, Stunarone) is an anti-histamine which is mainly used for the control of nausea and vomiting due to motion sickness. Cinnarizine could be also viewed as a nootropic drug because of its vasorelaxating abilities (due to calcium channel blockage) and as a labyrinthine sedative (Towse et al., 1980). A clinical evaluation of cinnarizine in various allergic disorders has been reported earlier (Barrett et al., 1960). Cinnarizine can be used in scuba divers without an increased risk of central nervous system oxygen toxicity. The crystal structures of some related compounds viz.
cinnarizine (Mouillé et al., 1975) and cyclizine hydrochloride (Bertolasi et al., 1980) have been reported. In view of the above, and as a part of our studies on the salts of the piperazines, the title compound was synthesized and herein we report its crystal structure.
The molecular structure and atom numbering scheme of the title compound are shown in Fig 1. In the structure, the piperazine ring adopts a slightly distorted chair conformation with the puckering parameters Q, θ and φ having values of 0.584 (2)°, 174.3 (2)° and 179 (2)°, respectively (Cremer & Pople, 1975). These values slightly different from those reported earlier for cinnarizinium dipicrate (Jasinski et al., 2011). For an ideal chair conformation, θ has a value of 0 or 180°. The sum of the bond angles around the piperazine-N atoms N1 and N2 are 328.94° and 332.45°, respectively, indicating that they are sp 3 hybridized. The bonds N1-C7 and N2-C18 connecting the diphenylmethyl and the phenylbut-2-ene groups make an angle of 74.44 (14)° and 70.28 (14)°, respectively, with the Cremer and Pople (1975) plane of the piperazine ring and thus the substituents are in the equatorial plane. The dihedral angle between the piperazine ring and the phenyl ring (C21-C26) bridged by the but-2-ene group is 63.50 (12)° whereas the dihedral angles between the piperazine ring and the diphenyl methyl rings (C1-C6) and (C8-C13) are 77.63 (11)° and 89.85 (15)°, respectively. In the crystal structure, N-H···O hydrogen bonds link the ions into two ion aggregates.

Experimental
Cinnarizine (3.68 g, 0.01 mol) and picric acid (2.99 g, 0.01 mol) were dissolved separately in methanol. The solutions were mixed and stirred for a few minutes at room temperature. The precipitate was collected by filtration and purified by recrystallization from methanol. On recrystallization with DMF after 15 days, good quality single crystals were obtained; M.pt: 463-465 K.

Refinement
All H atoms were placed at calculated positions and refined using a riding model approximation, with C-H distances in the range 0.93-0.98 Å, and with U iso (H) = 1.2U eq (C). The ammonium-H atom was refined freely.

Figure 1
A view of the molecule structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.  Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.