Crystal structures of the two isomeric hydrogen-bonded cocrystals 2-chloro-4-nitrobenzoic acid–5-nitroquinoline (1/1) and 5-chloro-2-nitrobenzoic acid–5-nitroquinoline (1/1)

The structures of the two isomeric hydrogen-bonded 1:1 cocrystals of 5-nitroquinoline with 2-chloro-4-nitrobenzoic acid and 5-chloro-2-nitrobenzoic acid have been determined at 190 K. In each crystal, the acid and base molecules are linked by a short O—H⋯N hydrogen bond.


Figure 1
The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The O-HÁ Á ÁN hydrogen bond is indicated by a dashed line.

Figure 2
The molecular structure of (II), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The O-HÁ Á ÁN hydrogen bond is indicated by a dashed line.
ther by an O-HÁ Á ÁN hydrogen bond between the carboxy group and the N atom of the base ( Fig. 1 and Table 1  3.94 (17) and 7.5 (5) , respectively, with the benzene ring (C1-C6) and the carboxy group (O1/C7/O2). In the acid molecule, the benzene ring makes dihedral angles of 4.3 (5) and 2.5 (5) , respectively, with the carboxy group and the nitro group (O3/ N1/O4), while in the base molecule, the quinoline ring system and the attached nitro group (O5/N3/O6) are somewhat twisted with a dihedral angle of 36.2 (5) . The molecular structure of (II) is shown in Fig. 2. Similar to (I), the acid and base molecules are held together by an O-HÁ Á ÁN hydrogen bond (Table 2). In the acid-base unit, the quinoline ring system and the hydrogen-bonded carboxy group are almost coplanar, with a dihedral angle of 2.9 (2) , while the quinoline ring system and the benzene ring of the acid are twisted with respect to each other by a dihedral angle of 37.37 (6) . In the acid molecule, the benzene ring makes dihedral angles of 40.3 (2) and 47.12 (19) , respectively, with the carboxy and nitro groups. In the base molecule, the dihedral angle between the quinoline ring system and the attached nitro group is 11.3 (2) .

Supramolecular features
In the crystal of (I), the hydrogen-bonded acid-base units are linked by a C-HÁ Á ÁO hydrogen bond (C13-H13Á Á ÁO4 ii ; symmetry code as in Table 1), forming a tape structure along [120]. The tapes are stacked into a layer parallel to the ab plane ( Fig. 3) via N-OÁ Á Á contacts (N3-O5Á Á ÁCg3 iii and N3-O5Á Á ÁCg4 iii ; Table 1) between the nitro group of the base and the quinoline ring system; Cg3 and Cg4 are the centroids of the C11-C16 ring and the N2/C8-C16 ring system of the base molecule, respectively. The layers are further linked by other C-HÁ Á ÁO hydrogen bonds (C8-H8Á Á ÁO2 i and C9-H9Á Á ÁO2 i ; Table 1), forming a three-dimensional network.

Refinement
Crystal data, data collection, and structure refinement details are summarized in Table 3. All H atoms in compounds (I) and (II) were found in difference Fourier maps. H atoms on O atoms in (I) and (II) were refined freely, with distances of O1-H1 = 1.02 (8) Å in (I) and O1-H1 = 0.99 (4) Å in (II). Other H atoms were positioned geometrically (C-H = 0.95 Å ) and treated as riding, with U iso (H) = 1.2U eq (C). For both structures, data collection: PROCESS-AUTO (Rigaku, 2006); cell refinement: PROCESS-AUTO (Rigaku, 2006); data reduction: PROCESS-AUTO (Rigaku, 2006); program(s) used to solve structure: SHELXT2018 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: CrystalStructure (Rigaku, 2018) and PLATON (Spek, 2015).  (6) 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.