1,1′-Dimethyl-4,4′-[(2,4-diphenylcyclobutane-1,3-diyl)dipyridinium–(E)-1-methyl-4-styrylpyridinium–benzenesulfonate (0.15/1.70/2)

In the title compound, 1.70C14H14N+·0.15C28H28N2 2+·2C6H5O3S−, the monocation exists in the E configuration with respect to the ethenyl C=C double bond and is close to planar, the dihedral angle between the pyridinium and phenyl ring being 5.20 (13)°. The dication lies about an inversion centre. In the crystal, the dication occupies almost the same site occupied by monocations at (x, y, z) and (2 − x, 1 − y, 1 − z). The O atoms of the anion are disordered over two positions with occupancies of 0.75 and 0.25. In the crystal, the cations are stacked in an antiparallel manner along the a axis, whereas the anions are linked into chains along the same direction by C—H⋯O hydrogen bonds. In addition, C—H⋯π and π–π interactions [centroid–centroid distance = 3.593 (9) or 3.6705 (16) Å] are observed.

In the title compound, 1.70C 14 H 14 N + Á0.15C 28 H 28 N 2 2+ Á-2C 6 H 5 O 3 S À , the monocation exists in the E configuration with respect to the ethenyl C C double bond and is close to planar, the dihedral angle between the pyridinium and phenyl ring being 5.20 (13) . The dication lies about an inversion centre. In the crystal, the dication occupies almost the same site occupied by monocations at (x, y, z) and (2 À x, 1 À y, 1 À z). The O atoms of the anion are disordered over two positions with occupancies of 0.75 and 0.25. In the crystal, the cations are stacked in an antiparallel manner along the a axis, whereas the anions are linked into chains along the same direction by C-HÁ Á ÁO hydrogen bonds. In addition, C-HÁ Á Á andinteractions [centroid-centroid distance = 3.593 (9) or 3.6705 (16) Å ] are observed.

Comment
Recently, there is considerable interest in the synthesis of new materials with large second-order optical nonlinearities. Such materials require both molecular hyperpolarizability and orientation in a noncentrosymmetric arrangement (Lin et al., 2002).
Taking advantage of our previous experience in the crystal growth of some pyridinium derivatives (Chanawanno et al., 2008;Chantrapromma et al., 2009a,b;Fun et al., 2009a,b), we report the synthesis and crystal structure of the title compound in which the dication is resulted from the unexpected [2+2] cycloaddition of the monocation. The title compound crystallizes in the centrosymmetric space group P1 and does not exhibit second-order nonlinear optical properties. to the monocation, with the dihedral angles between the mean plane through C1-C6 with N1/C7-C11 and C14-C19 being 87.56 (11) and 82.36 (12)°, respectively. Bond lengths are comparable with those in related structures (Chantrapromma et al., 2009a,b;Fun et al., 2009a,b).

Experimental
Silver (

Refinement
The fractional occupancies of the monocation and dication were initially refined to 0.847 (3)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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.