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The crystal used for structure determination contained, along with the title compound, C 17 H 14 BrN 3 O 4 , an admixture [0.0324 (11)] of its 7-bromo isomer. The 2,3-di-hydro-1 H -indole ring system is nearly planar, while the conformation of the 4 H -pyran ring is close to a flattened boat. The mean planes of these fragments form a dihedral angle of 86.67 (9)°. The carboxyl-ate group lies near the plane of 4 H -pyran, its orientation is stabilized by an intra-molecular C-H⋯O contact. In the crystal, the mol-ecules are connected into layers by N-H⋯N and N-H⋯O hydrogen bonds. The most important contributions to the crystal packing are from H⋯H (33.1%), O⋯H/H⋯O (16.3%), N⋯H/H⋯N (12.1%), Br⋯H/H⋯Br (11.5%) and C⋯H/H⋯C (10.6%) inter-actions., (© Naghiyev et al. 2022.)

In 2-amino-4-(4-bromo-phen-yl)-6-oxo-1-phenyl-1,4,5,6-tetra-hydro-pyridine-3-carbo-nitrile hemihydrate, C 18 H 14 BrN 3 O·0.5H 2 O, (I), pairs of mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming dimers with an R 2 2 (12) ring motif. The dimers are connected by N-H⋯Br and O-H⋯O hydrogen bonds, and C-Br⋯π inter-actions, forming layers parallel to the (010) plane. 1,6-Di-amino-2-oxo-4-phenyl-1,2-di-hydro-pyridine-3,5-dicarbo-nitrile, C 13 H 9 N 5 O, (II), crystallizes in the triclinic space group P with two independent mol-ecules (IIA and IIB) in the asymmetric unit. In the crystal of (II), mol-ecules IIA and IIB are linked by inter-molecular N-H⋯N and N-H⋯O hydrogen bonds into layers parallel to (001). These layers are connected along the c- axis direction by weak C-H⋯N contacts. C-H⋯π and C-N⋯π inter-actions connect adjacent mol-ecules, forming chains along the a- axis direction. In (I) and (II), the stability of the packing is ensured by van der Waals inter-actions between the layers. In (I), Hirshfeld surface analysis showed that the most important contributions to the crystal packing are from H⋯H (37.9%), C⋯H/H⋯C (18.4%), Br⋯H/H⋯Br (13.3%), N⋯H/H⋯N (11.5%) and O⋯H/H⋯O (10.0%) inter-actions, while in (II), H⋯H inter-actions are the most significant contributors to the crystal packing (27.6% for mol-ecule IIA and 23.1% for mol-ecule IIB)., (© Naghiyev et al. 2022.)

Compounds (I), C 9 H 10 N 2 O 4 , (II), C 11 H 12 N 2 O 4 , and (III), C 14 H 12 N 2 O 4 ·C 3 H 7 NO represent 9,9-disubstituted-3,7-di-aza-bicyclo-[3.3.1]nonane-2,4,6,8-tetra-one deriv-atives with very similar mol-ecular geometries for the bicyclic framework: the dihedral angle between the planes of the imide groups is 74.87 (6), 73.86 (3) and 74.83 (6)° in (I)-(III), respectively. The dimethyl derivative (I) is positioned on a crystallographic twofold axis and its overall geometry deviates only slightly from idealized C 2v symmetry. The spiro-cyclo-pentane derivative (II) and the phen-yl/methyl analog (III) retain only inter-nal C s symmetry, which in the case of (II) coincides with crystallographic mirror symmetry. The cyclo-pentane moiety in (II) adopts an envelope conformation, with the spiro C atom deviating from the mean plane of the rest of the ring by 0.548 (2) Å. In compound (III), an N-H⋯O hydrogen bond is formed with the di-methyl-formamide solvent mol-ecule. In the crystal, both (I) and (II) form similar zigzag hydrogen-bonded ribbons through double inter-molecular N-H⋯O hydrogen bonds. However, whereas in (I) the ribbons are formed by two trans -arranged O=C-N-H amide fragments, the amide fragments are cis -positioned in (II). The formation of ribbons in (III) is apparently disrupted by participation of one of its N-H groups in hydrogen bonding with the solvent mol-ecule. As a result, the mol-ecules of (III) form zigzag chains rather than the ribbons through inter-molecular N-H⋯O hydrogen bonds. The crystal of (I) was a pseudo-merohedral twin.