The cocrystal 10-(2-methyl-4-phenyl-1H-inden-6-yl)-10H-phenothiazine–10-(2-methyl-7-phenyl-1H-inden-5-yl)-10H-phenothiazine (0.54/0.46)

The title compound, 0.535C28H21NS.0.465C28H21NS, was synthesized by palladium-catalysed amination. The structure is composed of two isomeric molecules, viz. 10-(2-methyl-4-phenyl-1H-inden-6-yl)-10H-phenothiazine, and 10-(2-methyl-7-phenyl-1H-inden-5-yl)-10H-phenothiazine, in the refined ratio 0.535 (12):0.465 (12). The isomers differ by the localization of the double bond in the cyclopentadiene ring. There are two sites in the structure that are occupied by the isomers. The respective isomers are occupationally disordered in each site, the refined proportions being 0.640 (6):0.360 (6) and 0.43 (1):0.57 (1). Moreover, each isomeric molecule is chiral; due to the crystallographic centres of symmetry, the molecules are also present in enantiomeric pairs. The crystal structure is stabilized by weak π–π [C⋯C = 3.389 (2) Å] interactions.

In the title structure, all the bond lengths and angles show normal values (Allen et al., 1987;Allen, 2002;CSD (2007), version 5.29). In both isomers, the phenothiazine fragment is bent relative to the line connecting S1(S1') and N1(N1') atoms; the corresponding interplanar angles equal to 147.72 (3) and 147.69 (4)° for A and A' site, respectively. In each isomer, the six-membered 1,4-thiazine ring adopts the boat conformation. In each isomer, the indene ring is nearly planar (the mean deviations are 0.025° and 0.043Å for A and A', respectively). The indene rings are nearly perpendicular to the mean planes of the phenothiazine fragments (the interplanar angles are 84.24 (12) and 86.49 (12)° for A and A', respectively). The phenyl substituent at C5 (C5') atoms is rotated out of the plane of the indene ring (the interplanar angles are 41.96 (13) and 42.8 (2)° for A and A', respectively). The relative orientations of the molecular fragments are plausibly influenced by the steric repulsions of the closest hydrogen atoms. The molecules at the site A' form dimers by means of weak π-π interactions (C4'···C15'(-x, 2-y, -z), 3.389 (2) Å).

Refinement
All the H atoms except some of them in the disordered region could be distinguished in the difference electron density map. However, they were situated into the idealized positions and refined in the riding motion approximation with C-H distances equal to 0.98Å for the methyl groups, 0.95Å for the aryl carbon atoms, and 0.99Å for the carbon atoms of the cyclopentadiene ring in the sp 3 state. U iso (H)=1.5U eq (parent atom) for the methyls and U iso (H)=1.2U eq (parent atom) for the remaining atoms. For the methyl hydrogen atoms, AFIX 137 command was used (Sheldrick, 2008). In the A and A' sites, the molecules are occupatioanlly disordered, being a superposition of the isomers (Ia) and (Ib). The proportions of (Ia) to (Ib) in the sites A and A' were refined with isotropic thermal displacement parameters using EADP command to equalize thermal parameters for the corresponding atomic pairs: C1A and C1B; C1' and C1"; C2A and C2B; C2' and C2"; C3A and C3B; C3' and C3"; C10A and C1B; C10' C10". These proportions were fixed in further refinement. In the next step all the disordered carbon atoms were refined unisotropically. The disordered fragments of the sites A and A' were refined using the command SAME 0.005 0.005 for (C3A C2A C1A C10A), (C1B C2B C3B C10B), (C1' C2' C3' C10'), (C3" C2" C1" C10").
Figures Fig. 1. The view of the title molecules, showing the atom-numbering scheme and the displacement ellipsoids drawn at 50% probability level. The hydrogen atoms are shown as spheres of arbitrary radius. The major-occupied parts at the sites A and A' correspond to the isomers (Ia) and (Ib) respectively. The disorder is also shown for both sites A and A'. Bonding in the minor-occupied part is presented with open solid lines.

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.
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-supplementary materials sup-4 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.