6-Nitro-2,3-bis(thiophen-2-yl)quinoxaline

The structure of the title nitrobis(thiophen-2-yl)quinoxaline has been determined at 298 K.

The title compound, C 16 H 9 N 3 O 2 S 2 , was synthesized via a condensation reaction in refluxing acetic acid. One thienyl ring is nearly coplanar with the quinoxaline unit [dihedral angle = 3.29 (9) ], the other makes an angle of 83.96 (4) .

Structure description
6-Nitro-2,3-bis(thiophen-2-yl)quinoxaline crystallizes in space group P2 1 /c. All bond lengths and angles are within expected values. Unlike in the related molecule 5-nitro-2,3bis(thiophen-2-yl)quinoxaline (de Freitas et al., 2020), one thienyl ring and the nitro group in the title compound are nearly coplanar with the quinoxaline moiety. The nitro group makes a dihedral angle of 7.76 (14) with respect to the mean plane of the quinoxaline unit. A survey of the literature on other 6-nitroquinoxalines reveals that the nitro group is routinely nearly coplanar. The two thienyl rings make dihedral angles of 83.96 (4) and 3.29 (9) , for the rings with S1 and S2 respectively, with the mean plane of the quinoxaline unit. The coplanar thienyl ring sulfur atom is closer in proximity to the quinoxaline nitrogen atom, in the trans arrangement of Du & Zhao (2003). The other thienyl ring is nearly perpendicular to the plane of the quinoxaline; barely adopting the aforementioned authors cis arrangement. There are no intermolecular interactions of consequence. An ORTEP view is shown in Fig. 1 and a view of the unit cell along (010) is shown in Fig. 2.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1.

Funding information
This research was funded by a CCSU-AAUP research grant.

Figure 1
A view of 6-nitro-2,3-bis(thiophen-2-yl)quinoxaline (Farrugia, 2012). Displacement ellipsoids are drawn at the 50% probability level. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.51 e Å −3 Δρ min = −0.33 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.

data-2
IUCrData (2020). 5, x200203 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. H atoms were included in calculated positions with C-H distances of 0.93 Å and were included in the refinement in riding motion approximation with U iso = 1.2 of the carrier atom.