Crystal structure and Hirshfeld surface analysis of 2-(2-hydroxyphenyl)quinoline-6-sulfonamide

The asymmetric unit of 2-(2-hydroxyphenyl)quinoline-6-sulfonamide contains two crystallographically independent molecules. The crystal structure features hydrogen bonding and π–π stacking interactions.

We report here the synthesis, structural characterization and Hirshfeld surface analysis of a new quinoline derivative, 2-(2-hydroxyphenyl)quinoline-6-sulfonamide. This compound was prepared in a two-step reaction, viz. reflux and solvothermal (see Synthesis and crystallization section).

Supramolecular features
In the crystal of (I), the presence of sulfonamide group leads indeed to the formation of strong intermolecular N-HÁ Á ÁO hydrogen bonds (Table 1), generating supramolecular hydrogen-bonded layers parallel to the (010) plane (Fig. 3a).
The packing diagram of the title compound viewed down the a axis ( Fig. 3b) shows that the layers are stacked perpendicular to the b axis at (0,1/4,0) and (0,3/4,0). These layers are formed by aggregation of R 4 4 (14) ring motifs (Fig. 3c). In addition, the hydroxyl group of each molecule is involved in a C-HÁ Á ÁO hydrogen bond, forming an inversion dimer with an R 2 2 (16) graph-set motif. The dimers are linked by a further C-HÁ Á ÁO hydrogen bond involving one of the oxygen atoms of the sulfonamide group (Fig. 3d). Weak intermolecular C-HÁ Á Á interactions are also observed in the crystal packing, forming a chain along the a-axis direction (Fig. 3e Table 1 Hydrogen-bond geometry (Å , ).

Hirshfeld surface analysis
For further characterization of the intermolecular interactions in (I), we carried out a Hirshfeld surface (HS) analysis (Spackman & Jayatilaka, 2009) using CrystalExplorer (Spackman et al., 2021) and generated the associated twodimensional fingerprint plots (McKinnon et al., 2007). The HS of (I) mapped over d norm in the range À0.5231 to +1.1263 a.u. is illustrated in Fig. 5a using color to indicate contacts that are shorter (red areas), equal to (white areas), or longer than (blue areas) the sum of the van der Waals radii. The dominant interactions between sulfonamide N-H and O atoms can be seen as the bright-red areas marked as 1, 2, 3 and 4. The lightred spots labeled as 5, 6 and 7 are due to C-HÁ Á ÁO inter-actions. The weak C-HÁ Á Á contacts are indicated by the red ellipse.
The presence of characteristic triangles on the shape-index surface ( Fig. 5b) clearly indicate the presence ofinteractions between neighboring molecules while the curvedness plots ( Fig. 5c) show flat surface patches characteristic of planar stacking.
The overall two-dimensional fingerprint plot and those delineated into CÁ Á ÁH/HÁ Á ÁC, OÁ Á ÁH/HÁ Á ÁO, HÁ Á ÁH, CÁ Á ÁC and NÁ Á ÁH/HÁ Á ÁN contacts are illustrated in Fig. 6 together with their relative contributions to the Hirshfeld surface. The fingerprint plots show that the CÁ Á ÁH/HÁ Á ÁC contacts (29.2%)      Percentage contributions of contacts to the Hirshfeld surface in the title compound. make the largest contribution to the overall packing of the crystal ( Table 2, Fig. 7), which are related to the presence of C-HÁ Á Á interactions in the structure of (I) (Fig. 8c-d).
The second most important interactions are OÁ Á ÁH/HÁ Á ÁO contributing by 28.6% to the overall crystal packing (Table 2, Fig. 6), and are related to the presence of N-HÁ Á ÁO and C-HÁ Á ÁO interactions in the structure of (I) (Fig. 8a,b). In addition, van der Waals interactions (HÁ Á ÁH) are one of the major (28.5%) interactions in this structure. The presence of weakstacking interactions are reflected in the 5.2 and 1.2% contributions from CÁ Á ÁC and CÁ Á ÁN/NÁ Á ÁC contacts to the Hirshfeld surface. Other contacts make a contribution of 3.5% in total and are not discussed in this work.

Synthesis and crystallization
The title compound was prepared by a two-step reaction. First, an ethanol solution (5 mL) of 4-aminobenzenesulfonamide (0.33 g, 1.9 mmol) was added dropwise under stirring to an ethanol solution (5 mL) of 2-hydroxybenzaldehyde (0.2 mL, 0.234 g, 1.9 mmol) and refluxed for 2 h. After that, an acetone solution (5 mL) of palladium(II) acetate (0.05 g, 0.2 mmol) was added dropwise under stirring for 1 h. The yellow mixture was then transferred to a 25 mL Teflon-lined stainless-steel autoclave and sealed to heat at 393 K. After reaction for 48 h, the autoclave was cooled down to room temperature. Yellow block-like crystals suitable for X-ray diffraction analysis were obtained, isolated by filtration, washed with water and dried in air. Yield: 0.25 g, 43.44%.

Refinement
Crystal data, details of data collection, and results of structure refinement are summarized in Table 3. The hydrogen atoms of the sulfonamide NH 2 and hydroxyl groups were localized in a difference-Fourier map and refined with O-H = 0.84 AE 0.01 Å , and with U iso (H) set to 1.5U eq (O) or 1.2U eq (N). All other hydrogen atoms were placed in calculated positions with C-H = 0.95 Å and refined using a riding model with fixed isotropic displacement parameters [U iso (H) = 1.2U eq (C)].    program(s) used to solve structure: SHELXT2018/2 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and PLATON (Spek, 2020).

2-(2-Hydroxyphenyl)quinoline-6-sulfonamide
Crystal data 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.