1,2-Bis(2-methyl-5-phenyl-3-thienyl)benzene

In the molecule of the title compound, C28H22S2, the two thiophene rings are twisted with respect to the central benzene ring, making dihedral angles of 71.59 (12) and 50.71 (12)°. The two terminal benzene rings are oriented at dihedral angles of 37.59 (11) and 20.12 (11)° to their bonded thiophene rings.

In the molecule of the title compound, C 28 H 22 S 2 , the two thiophene rings are twisted with respect to the central benzene ring, making dihedral angles of 71.59 (12) and 50.71 (12) . The two terminal benzene rings are oriented at dihedral angles of 37.59 (11) and 20.12 (11) to their bonded thiophene rings.

Data collection
Bruker SMART CCD area-detector diffractometer Absorption correction: multi-scan (SADABS; Sheldrick, 1996)  Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL software used to prepare material for publication: SHELXTL. This work was supported by the Science Fund of the Education Office of Jiangxi (GJJ09306, GJJ09302) and the Youth Science Fund of the Education Office of Jiangxi (GJJ09572).

S1. Comment
The design and synthesis of photochromic molecules is an area of intense research because of the widespread use in photonic device applications such as memory media and optical switching (Irie et al. 2001). To date, four kinds of diarylethenes with different bridge units have been reported, that is diarylethenes with a perfluorocyclopentene moiety (Peters et al. 2003), diarylethenes with maleic anhydride and maleimide moieties (Yamaguchi et al. 1997), diarylethenes with a cyclopentene moiety (Lucas et al. 1998), and diarylethenes with a 2,5-dihydrothiphene moiety (Chen & Zeng, 2004). One of our research goals is to develop a novel diarylethene derivative with the inexpensive benzene ring as bridge unit. In this paper, the ORTEP drawing of the single-crystal shows the title compound, i.e. 1,2-(2-methyl-5-phenyl-3thienyl)benzene, packed in a parallel conformation which is very rare in other diarylethene system. The two independent planar thiophene ring systems have essentially identical geometries, and the dihedral angles between the central benzenering and these of the two thiophene rings, S1/C7-C10, and S2/ C18-C21 are 71.6 (4)° and 50.5 (7)°. The two thiophene groups are linked by the central benzene-ring, with both of them attached to the ethylene group via the 2-position.
The distance between the two C atoms (C8···C19) is 4.06 (7) Å, which is short enough, theoretically, for the ring-closure reaction to take place in the crystalline phase (Ramamurthy & Venkatesan, 1987), but the crystals of the title compound is parallel thiophene-ring, so, the crystals cannot show photochromism.
The title compound was prepared by adding compound (2) (0.88 g, 4.05 mmol) with Na 2 CO 3 (2.00 mol/L, 60.00 mmol) to a stirred THF solution (50 ml) containing 1,2-dibromobenzene (0.48 g, 2.03 mmol) and Pd(PPh 3 ) 4 (0.27 g) at 293 K under a nitrogen atmosphere. After reflux for 16 h, the reaction mixture was extracted with ether, evaporated in vacuo and purified by column chromatography on SiO 2 using petroleum ether as the eluent to obtain the title compound. Single crystals of the title compound (1a) were grown from a chloroform solution by slow evaporation (m.p. 404.8-405.2 K).

S3. Refinement
H atoms were placed in calculated positions and treated as riding with C-H = 0.96 Å (methyl) or 0.93 Å (aromatic), U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (C) for the others.  Molecular view the atom-labeling scheme. Ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii.

Figure 2
The preparation of the title compound.

1,2-Bis(2-methyl-5-phenyl-3-thienyl)benzene
Crystal data   125.51, 126.00, 127.00, 127.26, 128.76, 130.61, 134.60, 135.03, 136.09, 139.01, 139.45. IR (KBr, cm -1 ): 756, 766, 849, 908, 946, 1001, 1029, 1073, 1153, 1184, 1227, 1377, 1462, 1479, 1505, 1596, 1629, 2854, 2924 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.8690 (