Crystal structures of 2,3-bis(thiophen-2-yl)pyrido[2,3-b]pyrazine and 7-bromo-2,3-bis(thiophen-2-yl)pyrido[2,3-b]pyrazine

• Main Authors: Rafal Popek, Guy Crundwell
• Format: Article
• Language: English
• Published: International Union of Crystallography 2019-01-01
• Series: Acta Crystallographica Section E: Crystallographic Communications
• Subjects: crystal structure; pyrido[2,3-b]pyrazines; offset π-π interactions; hydrogen bonding
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S2056989018016882

The crystal structures of 2,3-bis(thiophen-2-yl)pyrido[2,3-b]pyrazine, C15H9N3S2 (1), and 7-bromo-2,3-bis(thiophen-2-yl)pyrido[2,3-b]pyrazine, C15H8BrN3S2 (2), are discussed. Both molecules crystallize in space group P21/c. In 1, the thienyl rings are inclined to the mean plane of the pyridopyrazine moiety by 6.16 (7) and 86.66 (8)°, where as in 2 the corresponding dihedral angles are 33.29 (11) and 19.84 (9)°. The pyridopyrazine moiety is relatively planar in 1 with the two rings being inclined to each other by 1.33 (7)°. In 2, however, the pyridopyrazine moiety is buckled with the corresponding dihedral angle being larger at 8.78 (10)°. In the crystal of 1, the packing creates intersecting bilayers; the layering results from the pyridopyrazine moieties being engaged in offset π-stacking, where the interplanar distance is 3.431 (9) Å with an offset 1.14 Å. In the crystal of 2, the molecules pack head-to-head and are linked by a series of C—H...Br and C—H...N intermolecular interactions, forming layers parallel to the ab plane.