2-(5,6-Diphenyl-1,2,4-triazin-3-yl)aniline

The title compound, C21H16N4, obtained under standard Suzuki cross-coupling conditions, is a model compound in the synthesis and biological activity evaluation of new aza-analogues of sildenafil containing a pyrazolo-[4,3-e][1,2,4]triazine system. An N-H⋯N intra-molecular hydrogen bond involving the amino-benzene system and the 1,2,4-triazine moiety helps to establish a near coplanar orientation of the rings with a dihedral angle of 12.04 (4)°, which is believed to be necessary for the biological activity of sildenafil analogues. The 1,2,4-triazine ring is slightly distorted from planarity [r.m.s deviation = 0.0299 (11) Å] and forms dihedral angles of 58.60 (4) and 36.35 (3)° with the pendant phenyl rings. The crystal packing features bifurcated N-H⋯(N,N) hydrogen bonds linking screw-axis-related mol-ecules into chains parallel to the [010] direction and π-π inter-actions, with a centroid-centroid separation of 3.8722 (7) Å and a slippage of 1.412 (3) Å. The crystal studied was a nonmerohedral twin with a ratio of 0.707 (2):0293 (2).