Received 6 September 2012
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-HN intramolecular hydrogen bond involving the aminobenzene 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 molecules into chains parallel to the  direction< and - interactions, 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).
For background information on the activity of sildenafil citrate, see: Terrett et al. (1996); Card et al. (2004). For the synthesis of the title compound, see: Agarwal et al. (2010). For a description of the Cambridge Structural Database, see: Allen (2002); Bruno et al. (2002).
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 2012).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LR2082 ).
This research was supported by grant No. NN405 092340 from the National Science Centre, Poland.
Agarwal, P. K., Saifuddin, M. & Kundu, B. (2010). Tetrahedron, 66, 862-870.
Allen, F. H. (2002). Acta Cryst. B58, 380-388.
Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruno, I. J., Cole, J. C., Edgington, P. R., Kessler, M., Macrae, C. F., McCabe, P., Pearson, J. & Taylor, R. (2002). Acta Cryst. B58, 389-397.
Card, G. L., England, B. P., Suzuki, Y., Fong, D., Powell, B., Lee, B., Luu, C., Tabrizizad, M., Gillette, S., Ibrahim, P. N., Artis, D. R., Bollag, G., Milburn, M. V., Kim, S. H., Schlessinger, J. & Zhang, K. Y. (2004). Structure, 12, 2233-2247.
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Terrett, N. K., Bell, A. S., Brown, D. & Ellis, P. (1996). Bioorg. Med. Chem. Lett. 6, 1819-1824.