Crystal structure of 1,3-bis(2,3-dimethylquinoxalin-6-yl)benzene

The molecular structure of the title complex is composed of a central benzene ring with 3-dimethylquinoxalin-6-yl groups at the 1 and 3 positions. There are intermolecular π–π interactions which result in a two-dimensional extended structure. The layers extend parallel to the ab plane and stack along the c axis.


Chemical context
The title complex, (I), is one of the 1 st generation of quionoxaline-terminated polyphenylene dendrimers that were prepared to study the effect of multivalency on the electrochemistry of quinoxalines (Carino et al., 2015). The synthesis is based on C-H iridium-catalyzed borylation (Cho et al., 2002) followed by Suzuki coupling, which was previously used in our group in the preparation of polyphenylene dendrimers (Finke & Moore, 2008).

Supramolecular features
The molecules of (I) form extended layers via intermolecular interactions linking each molecule to its four nearest neighbors, Fig. 2a,b. The two-dimensional layers lie parallel to the ab-plane and stack along the c axis, Fig. 2c. The interactions occur between the central benzene ring and one of the heterocycles on a neighboring molecule. The orientation of these interacting groups is between 'parallel offset' and 'perpendicular t-shaped' as the C3-H3A bond points towards the C7 ii -N1 ii -C8 ii -C9 ii -N2 ii -C10 ii ring centroid [symmetry code: (ii) x + 1 2 , y + 1 2 , z]. The dihedral angle between a best fit plane through the C1-C2-C3-C4-C3 i -C2 i [symmetry code: (i) Àx + 1, y, Àz + 1 2 ] ring and a best-fit plane through the C7 ii -N1 ii -C8 ii -C9 ii -N2 ii -C10 ii ring is 41.70 (11) . The distance between the centroid of C7 ii -N1 ii -C8 ii -C9 ii -N2 ii -C10 ii ring A plot of (a) a two-dimensional layer of (I), (b) a molecule of (I) highlighted in yellow showing it interacting with its four nearest neighbors, and (c) a view along the a axis showing the separation between the layers and an overlay of the unit cell. All H atoms have been omitted for clarity. The intermolecular interactions are indicated by red dashed lines. and C3 is 3.311 (3)Å . The centroid(C7-N1-C8-C9-N2-C10)Á Á Ácentroid(C7-N1-C8-C9-N2-C10) distance between the layers of 4.721 (3)Å is too long to be considered another interaction. It appears the methyl groups on the quinoxaline prevent the layers from coming closer together.
The five 2,3-dimethylquinoxaline structures have a range of the dihedral angle between a best-fit plane through the sixmembered carbon ring and a best-fit plane through the sixmembered nitrogen heterocycle of 0.02 (5)-1.59 (7) . The two crystallographically independent molecules of the nitrosubstituted compound have dihedral angles of 0.18 (3) and 1.07 (2) , while this angle is 4.93 (2) for the dimeric complex. The methyl groups for all of these molecules lie slightly out of the plane of the heterocycle with a range of N-C-C-Me torsion angles of 176.64 (7)-179.90 (5) . The methyl groups in the database compounds range from nearly coplanar [Me-C-C-Me, = 0.09 (11) ] to significantly more twisted out of plane [Me-C-C-Me, = 3.33 (5) ]. Similar to (I), the dimeric molecule deviates significantly from being a planar molecule with a C2-C1-C1 iii -C2 iii [symmetry code: (iii) Àx, y, 1 2 À z] torsion angle of À43.40 (10) between the two 2,3-dimethylquinoxaline moieties.
combined organic layers were washed with water and brine, and dried over anhydrous MgSO 4 . Column chromatography on silica gel eluting with 8:2 hexane:EA to provide (I) (312.2 mg). Suitable single crystals were grown from slow diffusion of hexanes into a dichloromethane solution of (I

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