Carbinoxaminium dipicrate

In the dication of the title salt, C16H21ClN2O2+·2C6H2N3O7 − [systematic name: 2-{(4-chlorophenyl)[2-(dimethylazaniumyl)ethoxy]methyl}pyridinium bis(2,4,6-trinitrophenolate), contains a carbinoxaminium dication and two picrate anions, which are held together through intermolecular N—H⋯O hydrogen bonds. In the dication, the two aromatic rings form a dihedral angle of 80.1 (1)°. In the two independent picrate anions, the nitro groups are twisted from the benzene plane, the largest dihedral angle in each ion being 42.8 (1) and 81.1 (5)°. In the crystal, in addition to the classical N—H⋯O hydrogen bonds, weak C—H⋯O hydrogen bonds and π–π interactions between the aromatic rings of the anions [centroid–centroid distances of 3.5768 (15) and 3.7436 (15) Å] help to establish the packing.


Experimental
The asymmetric unit of (I) (Fig. 1) contains a carbinoxaminium dication and two picrate anions, which are held together through intermolecular N-H···O hydrogen bonds (Table 1). In the dication, the pyridine ring contains a positively charged N atom with quaternary character at the 2 position and a second positive quaternay N atom at the amino group.
The two aromatic rings form a dihedral angle of 80.1 (1)°. In picrate anion A, the mean plane of the N1A/C2A/O2A/O3A group is twisted by 42.8 (1)° from the attached benzene ring. In picrate anion B, the mean plane of the N1B/C2B/O2B/O3B group is twisted by 81.1 (5)° from the attached benzene ring. In the crystal, N-H···O hydrogen bonds and weak intermolecular C-H···O interactions between the cation and anion (Table 1) and /p-/p stacking interactions between the benzene rings with the intercentroid distances of 3.5768 (15) and 3.7436 (15) Å contribute to packing stability.

Refinement
Amino atom H1 was located on a difference map and isotropically refined. All the rest H atoms were geometrically positioned (C-H 0.95-1.00 Å; N-H 1.00 Å), and then refined as riding, with U iso =1.2 -1.5 U eq of the parent atom.

Figure 1
A content of asymmetric unit of (I) showing the atomic labeling and 30% probability displacement ellipsoids. Dashed lines indicate N-H···O hydrogen bonds. C-bound H atoms were omitted for clarity.

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.