Molecular and Crystal Structure of 7,7-dimethyl-2-pyridin-4-yl- 6,7-dihydro-1,2,4-triazolo[1,5-a][1,3,5]triazin-5-amine [1]

When crystallized from ethanol,


Introduction
Compounds with 1,2,4-triazolo[1,5-a]triazine ring system have not been found in nature.However, this heterocyclic system resembles purine which is one of the most important heterocycles in nature.The additional bridge nitrogen atom of 1,2,4-triazolo [1,5-a]triazines makes them 5-azaisosters of purines.The chemistry and biological activity of 1,2,4-triazolo [1,5-a]triazines have been extensively explored and this heterocyclic system has been well recognized as a promising scaffold for the construction of molecules with diverse biological effects [2].

Results and Discussion
Crystals suitable for the X-ray diffraction analysis were obtained by recrystallization from ethanol (colorless blocks, m.p. 302 °C).The crystal and instrumental parameters used in the unit cell determination and data collection are summarized in Table 1.

Experimental Section
The X-ray diffraction data for the compound were measured at room temperature on a Bruker SMART APEX CCD diffractometer using Mo Kα (λ = 0.71073 Å) radiation.The empirical absorption corrections were applied by the multi-scan method using SADABS [21].Intensity data were collected in the ω-φ scan mode using SMART [22] and were reduced using SAINT [22].The structure was solved by direct methods using SHELXS97 [23] and difference Fourier synthesis using SHELXL97 [23].The positions and anisotropic displacement parameters of all non-hydrogen atoms were included in the full-matrix least-square refinement using SHELXL97 [23] and the procedures were carried out for a few cycles until convergence was reached.A total of 8323 reflections were collected, resulting in 2736 (R int = 0.037) independent reflections of which the number of reflections satisfying I > 2σ(I) criteria was 2282.All the N-bound hydrogen atoms were located in a difference map and refined freely.The hydrogen atoms attached to the carbon atoms were placed in calculated positions (0.94 Å for C aryl -H and 0.97 Å for the methyl groups) and included in the final cycles of refinement using a riding model, with U iso (H) = 1.2U eq (C aryl ) and U iso (H) = 1.5U eq (C methyl ).A rotating group model was used for the methyl groups.The R factor for observed data finally converged to R 1 = 0.0476 with wR 2 = 0.1188 in the compound.The maximum and minimum values of residual electron density were 0.268 and -0.213 eÅ -3 .The geometry calculations were performed using PLATON [24].SHELXTL [23] and MERCURY [25] were used for the diagram generation.

Figure 3 .
Figure 3.A view of the crystal packing in 1 along the c axis, showing the C(4)C(6) chain of molecules formed by the NH•••N hydrogen bonds running parallel to the [101] direction.

Figure 4 .
Figure 4.A view of the crystal packing in 1 along the c axis, showing the C(11) chain of molecules formed by the NH•••N hydrogen bonds running parallel to the [010] direction.
a][1,3,5] triazin-5-amine has been determined and compared with structurally similar molecules.The classical NH•••N hydrogen bonds and C-H•••π interactions stabilizing packing of the molecules in the crystal has been described.