Crystal structures of 1-(4-chlorophenyl)-4-(4-methylphenyl)-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carboxylic acid and 4-(4-methoxyphenyl)-1-(4-methylphenyl)-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile

The asymmetric units of compounds I and II both consist of two independent molecules. In the crystal of I, molecules are linked through N—H⋯O hydrogen bonds, forming inversion dimers with (8) ring motifs and with their molecular planes parallel to (020). C—H⋯O interactions connect the dimers, forming a three-dimensional network. In the crystal of II, molecules are linked by C—H⋯N, C—H⋯O and C—H⋯π interactions, resulting in a three-dimensional network.

In compounds I and II, the observed bond lengths and bond angles are in good agreement with the reported experimental values as found in the structures of HUYVUU, TEJQII, TEJQOO, AZOWAO, XECCAL and XAYVEA. The metrical parameters are, hence, unremarkable.
The angles between the planes of the two benzene rings in I and II are 52.64 (11) for IA, 33.78 (12) for IB, 21.80 (11) for IIA and 19.39 (11) for IIB, respectively. These angles are notably distinct, even for the two independent molecules in each structure. They are all also significantly larger than the value of 11.52 (7) found in HUYVUU (the only other example with two benzene rings amongst the related struc- A view of the C-HÁ Á Á interactions in II shown as dashed lines. [Symmetry codes: (a) 1 À x, 1 À y, 1 À z; (b) 2 À x, 1 À y, 1 À z].

Figure 3
The crystal packing of I viewed down the b axis showing intermolecular hydrogen bonds as dashed lines. tures). Intermolecular interactions can be weaker or stronger based on the presence or absence or difference of functional groups and the molecular environment, depending on the crystal system, which all affect the molecular conformation. The observed difference in the angles between the two benzene rings may be attributed to these factors.
K values, which are large only for weak reflections with an F c /F cmax ratio less than 0.005 and less than 0.015 for I and II, respectively, were observed as 2.713 for I and 5.559 for II.

Refinement
Refinement on F 2 Least-squares matrix: full where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.66 e Å −3 Δρ min = −0.55 e Å −3 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 Occ.