Date Published: June 01, 2011
Publisher: International Union of Crystallography
Author(s): Sebastian Moschel, Dieter Schollmeyer, Heiner Detert.
The title compound, C22H26N4, was prepared from p-dimethylaminopropiophenone in six steps. The molecule has no crystallographic symmetry. The dihedral angles between the pyrazine ring and the phenyl rings are 35.81 (6) and 37.11 (8)°. The dimethylamino groups are essentially planar (sum of the bond angles at N = 359.3 and 359.9°) and nearly coplanar with the adjacent aromatic ring [dihedral angles = 5.54 (11) and 7.40 (3)°]. This effect and the short aniline C—N bonds can be rationalised in terms of charge transfer from the amino groups to the central pyrazine ring.
The title compound was prepared as a fundamental chromophore and as an intermediate for the preparation of acidochromic dyes, see: Detert & Sugiono (2005 ▶); Schmitt et al. (2008 ▶); Nemkovich et al. (2010 ▶). Conjugated oligomers with a pyrazine center and lateral donors are solvatochromic probes, see: Collette & Harper (2003 ▶) and Schmitt et al. (2011 ▶). 2,5-Diphenylpyrazine shows interplanar angles of about 21° (Pieterse et al., 2000 ▶); due to steric hindrance these angles are opened up to 37–49° in the tetraphenylpyrazine (Bartnik et al., 1999 ▶). The planarization of terminal amino groups and short aniline C—N bonds due to strong electronic coupling has also been observed in 2,5-bis(p-dimethylaminostyryl)pyrazine, see: Fischer et al. (2011 ▶).