Crystal structure and Hirshfeld surface analysis of 6-amino-8-phenyl-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrimidine-7,9-dicarbonitrile

In the crystal of the title compound, the molecules form dimers with centrosymmetric (12) motifs linked by pairwise N—H⋯N hydrogen bonds and C—H⋯N contacts connect these dimers into double layers.

As part of our ongoing studies in this area (Naghiyev et al., 2021), we now report the crystal structure and Hirshfeld surface analysis of the title compound, C 16 H 15 N 5 (I), obtained by a three-component synthesis (Naghiyev, 2019). ISSN 2056-9890

Supramolecular features
In the crystal, pairwise N1-H1Á Á ÁN17 hydrogen bonds link the molecules into centrosymmetric dimers with R 2 2 (12) motifs (Table 1) and C8-H8Á Á ÁN10 contacts connect these dimers to form double layers lying parallel to (001) (Figs. 2 and 3). The layers are consolidated by C-HÁ Á Á and N-HÁ Á Á interactions and weak van der Waals interactions occur between the layers. The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

Hirshfeld surface analysis
The nature of the intermolecular interactions in (I) were examined with CrystalExplorer17.5 (Turner et al., 2017), using Hirshfeld surfaces (Spackman & Jayatilaka, 2009) and twodimensional fingerprint plots. The Hirshfeld surfaces mapped over d norm (Fig. 4) show the intermolecular contacts as redcoloured spots, which indicate the closer contacts of the N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds.
In the molecule of HECLUZ, the seven-membered pentamethylene ring adopts a twist-boat conformation. In the crystal, hydrogen bonds with a 16-membered ring and a chain motif are generated by N-HÁ Á ÁN and N-HÁ Á ÁO contacts. The hydrogen-bonded chains formed along [100] are connected by aromaticstacking interactions observed between the pyridine and pyrimidine rings. In the crystal of VAMBET, the molecules are linked via C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds, forming layers lying parallel to (101). In LEGLIU, the molecular structure is built up with two fused six-membered rings and one seven-membered ring linked through a spiro C atom. The crystal packing features N-HÁ Á ÁO hydrogen bonds. In KUTPEV, the water molecules are mutually O-HÁ Á ÁO hydrogen bonded and form infinite chains propagating along the b-axis direction. Neighboring chains are linked by the quinazoline molecules by means of O-HÁ Á ÁO C hydrogen bonds, forming a two-dimensional network.

Synthesis and crystallization
The title compound was synthesized using our previously reported procedure (Naghiyev, 2019), and colourless prisms were obtained upon recrystallization from methanol solution. The three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range À0.47 to +1.30 a.u.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were placed in calculated positions (C-H = 0.95-1.00 Å ) and refined as riding atoms with U iso (H) = 1.2U eq (C). The N-bound H atoms were located in difference maps and their positions were freely refined with the constraint U iso (H) = 1.2U eq (N) applied.  program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020). Extinction correction: SHELXL, Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.00309 (14) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq N1 0.6921 (