N,N′-Bis(2-thienylmethylene)benzene-1,4-diamine

The Schiff base, C16H12N2S2, has been synthesized by refluxing an ethanolic solution of thiophene-2-carbaldehyde and benzene-1,4-diamine. The center of the benzene ring is located on a crystallographic center of inversion. The dihedral angle between the benzene and thiophene rings is 63.6 (1)°.


Comment
During the past decades, Schiff bases have been intensively investigated not only because of their strong coordination capability but also due to diverse biological activities, such as e.g. antibacterial and antitumor activities (Andersen et al., 2005;Koizumi et al., 2005;Boskovic et al., 2003;Oshio et al., 2005). Here we report the structure of N,N'-bis-thiophene-2-ylmethylene-1,4-benzenediamine, which could be used as another Schiff base ligand in combination with metal ions.
The molecular structure of the title compound is depicted in Figure 1. The center of the phenyl ring represents a crystallographic center of inversion. The dihedral angle between the phenyl and thiophene rings is 63.6 (1)°. As it is expected the thiophene rings also are perfectly planar with a deviation of the S atom of 0.001 Å.
Experimental N,N'-Bis-thiophene-2-yl-methylene-1,4-benzenediamine was prepared according to the method reported in the literature (Kannappan et al., 2005). Thiophene-2-carboxaldehyde (0.02 mol) was added to a stirred ethanolic solution of p-phenylenediamine (0.01 mol). The reaction mixture was stirred about 3 h and then the mixture was allowed to stand at room temperature for about two days. Yellow crystals suitable for X-ray diffraction analysis were collected with a yield of 60%. Anal.

Refinement
All H atoms were placed in calculated positions with C-H = 0.93Å and refined as riding with U iso (H) = 1.2U eq (carrier).

Figures
Fig . 1. View of the molecular structure of the title compound, showing the atomic numbering scheme and 50% probability displacement ellipsoids. Atoms labeled with A at the symmetry positions (-x + 1,-y + 1,-z + 1). 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 Rfactors(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 S1 0.15131 (14