Crystal Structure Refinement for 3,5-Dimethyl-1,7-diphenyl-4-(2,4,6-trinitrophenyl)-2,6-diazahepta-2,4-diene and Crystal Structure Determination for Its Hydrochloride

The crystal structure of 3,5-dimethyl-1,7-diphenyl-4-(2,4,6-trinitrophenyl)-2,6-diazahepta-2,4-diene (I) has been refined by X-ray crystallography; the crystal structure of its hydrochloride, C₂₅H₂₄N₅O₆)⁺ Cl^- (II), has been determined. Crystals II are trigonal, space group P3₁₂₁, a = 12.110(3), c = 15.135(3) , Z = 3. The structures of I and II were solved by direct methods and refined by full-matrix least-squares analysis anisotropically to R = 0.065 (I) and 0.049 (II) for all 4083 (I) and 3720 (II) independent (taking into account anomalous scattering for II) measured reflections (CAD-4 automatic diffractometer, MoK ). The configuration and conformation of molecule I in crystal I differ strongly from those of cation II (with a protonated nitrogen-2 atom) in crystal II. In crystal II, cation II has a twofold symmetry axis coinciding with the 2 crystallographic axis; the Cl^- anion lies on the other 2 axis. In crystal II, cations II and Cl^- anions are linked by N-H...Cl^- type hydrogen bonds into infinite (along the z axis) helices around the 3₁ screw axes.