Crystal structures and Hirshfeld surface analyses of two new tetra-kis-substituted pyrazines and a degredation product.

The two new tetra-kis-substituted pyrazines, 1,1',1'',1'''-(pyrazine-2,3,5,6-tetra-yl) tetra-kis-(,-di-methyl-methanamine), CHN, (I) and ,','','''-[pyrazine-2,3,5,6-tetra-yltetra-kis-(methyl-ene)]tetra-kis-(-methyl-aniline), CHN, (II), both crystallize with half a mol-ecule in the asymmetric unit; the whole mol-ecules are generated by inversion symmetry. There are weak intra-molecular C-H⋯N hydrogen bonds present in both mol-ecules and in (II) the pendant -methyl-aniline rings are linked by a C-H⋯π inter-action. The degredation product, ,[(6-phenyl-6,7-di-hydro-5-pyrrolo-[3,4-]pyrazine-2,3-di-yl)bis(methyl-ene)]bis-(-methyl-aniline), CHN, (III), was obtained several times by reacting (II) with different metal salts. Here, the 6-phenyl ring is almost coplanar with the planar pyrrolo-[3,4-]pyrazine unit (r.m.s. deviation = 0.029 Å), with a dihedral angle of 4.41 (10)° between them. The two -meth-yl-aniline rings are inclined to the planar pyrrolo-[3,4-]pyrazine unit by 88.26 (10) and 89.71 (10)°, and to each other by 72.56 (13)°. There are also weak intra-molecular C-H⋯N hydrogen bonds present involving the pyrazine ring and the two -methyl-aniline groups. In the crystal of (I), there are no significant inter-molecular contacts present, while in (II) mol-ecules are linked by a pair of C-H⋯π inter-actions, forming chains along the -axis direction. In the crystal of (III), mol-ecules are linked by two pairs of C-H⋯π inter-actions, forming inversion dimers, which in turn are linked by offset π-π inter-actions [inter-centroid distance = 3.8492 (19) Å], forming ribbons along the -axis direction.