2,2′-Bithiophene-3,3′-dicarbonitrile

The complete molecule of the title compound, C10H4N2S2, is generated by an inversion center situated at the mid-point of the bridging C—C bond. The bithiophene ring system is planar [maximum deviation = 0.003 (2) Å] and the central C—C bond length is 1.450 (2) Å. There are no significant intermolecular interactions in the crystal structure, which is stabilized by van der Waals interactions.


Related literature
For the importance of bithiophene derivatives, see: Katz et al. (1995). For their applications, see: Deng et al. (2011); Thomas et al. (2008). For background to the title compound, see: Demanze et al. (1996); Pletnev et al. (2002); For related structures, see: Benedict et al. (2004); Huang & Li (2011);Pelletier et al. (1995); Li & Li (2009) ;Teh et al. (2012). For thiophene C-S bond lengths, see: Howie & Wardell (2006). For the normal bonding picture for bithiophene, see: Khan et al. (2004). Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 2009). crystalline materials (Katz et al., 1995). Oligothiophenes and their derivatives are useful precursors for the construction of organic materials suitable for application in electronic devices (Deng et al., 2011;Thomas et al., 2008) and the presence of an electron-withdrawing cyano group may offer a route to tune the electronic properties of the resulting materials. Our interest in these derivatives has led us to prepare the title compound which is known in the literature (Pletnev et al., 2002;Demanze et al., 1996) but was obtained as a side product during the attempted synthesis of other derivatives. We herein report on the direct synthesis and the crystal structure of the title compound.
There are no significant hydrogen-bonding interactions in the crystal structure, which is stabilized by van der Waals interactions.

Experimental
Copper(I) cyanide (5.17 g, 57.72 mmol) was added to a solution of 3,3′-dibromo-2, 2′-bithiophene (6.23 g, 19.24 mmol) in 50 ml of DMF. This mixture was heated at 423 K for 32 h under nitrogen atmosphere. After cooling to room temperature, 50 ml of aqueous ammonia solution was added and allowed to stir for 4 h at room temperature. It was extracted with ethyl acetate and the combined organic layer washed with 3× 100 ml of water and dried over anhydrous sodium sulfate. On vacuum evaporation it produced a crude solid which was purified by column chromatography on silica gel using 4:1 mixture of hexanes and ethylacetate as eluant, to give a pale yellow solid; Yield 1.66 g (40%). Yellow block-like crystals were grown from an ethylacetate/hexane (1:4) mixture (M.p. 477 K). Spectroscopic data for the title compound are given in the archived CIF.

Refinement
All the H atoms were positioned geometrically and refined using a riding model: C-H = 0.93 Å with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title molecule showing the atom numbering. the displacement ellipsoids are drawn at the 50% probability level. 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.