2,3,5,6-Tetrafluoro-1,4-bis({[(thiophen-2-yl)methylidene]amino}methyl)benzene

In the title compound, C18H12F4N2S2, a bis-thiophenyl Schiff base ligand with a perifluorinated aromatic core, the complete molecule is generated by crystallographic inversion symmetry. The thiophene and tetrafluorinated benzene rings are oriented at a dihedral angle of 77.38 (4)°. The crystal structure exhibits C—H⋯F hydrogen bonds, resulting in supramolecular chains along the c-axis direction.

In the title compound, C 18 H 12 F 4 N 2 S 2 , a bis-thiophenyl Schiff base ligand with a perifluorinated aromatic core, the complete molecule is generated by crystallographic inversion symmetry. The thiophene and tetrafluorinated benzene rings are oriented at a dihedral angle of 77.38 (4) . The crystal structure exhibits C-HÁ Á ÁF hydrogen bonds, resulting in supramolecular chains along the c-axis direction.

Comment
In the past decade, thiophen-based bidentate Schiff base ligands have been utilized intensively to assemble various coordination compounds with intriguing structural features and potential applications (Hee & Soon, 2007;Fang et al., 2001). As part of our ongoing studies of the effect of fluorine substitution on crystal structures of coordination polymers (Chen et al., 2012), herein, we wish to report the crystal structure of the title compound, 2,3,5,6-tetrafluoro-1,4-bis(1-(1thiophen-2-yl)methyleneaminomethyl)benzene, (I).
A perspective view of (I), including the atomic numbering scheme, is shown in Fig. 1. (I) crystallizes around a crystallographic centre with a half molecule in the asymmetric unit. Bond lengths and angles are within normal ranges.
The terminal thiophenyl groups are coplanar, and they form a dihedral angle of 77.38 (4)° with the central tetrafluorinated benzene ring. Intermolecular C-H···F hydrogen-bonding interactions link the adjacent molecules to generate onedimensional supramolecular chains along the c axis (see Fig. 2).

Experimental
Compound (I) was synthesized and purified according to the method described by Zhang et al. (2011)  Colourless needle-like single crystals (m.p. 452.3-452.6 K) suitable for X-ray analysis were obtained by dissolving (I) (20.0 mg) in dichloromethane (6 ml) solution and then slowly evaporating the solvent at room temperature for a period of about one week.

Refinement
All H atoms bound to carbon were assigned to calculated positions, with C-H = 0.97 Å (methylene) and 0.93 Å (aromatic and imine), and refined using a riding model, with U iso (H)=1.2U eq (C).  Molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted for clarity.

Figure 2
View of the one-dimensional supramolecular chain structure constructed via intermolecular C-H···F hydrogen-bonding interactions (irrelative hydrogen atoms are omitted for clarity). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.28 e Å −3 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 > 2sigma(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.