Synthesis, crystal structure and Hirshfeld surface analysis of 3-(4-fluorophenyl)-2-formyl-7-methylimidazo[1,2-a]pyridin-1-ium chloride monohydrate

In the salt 3-(4-fluorophenyl)-2-formyl-7-methylimidazo[1,2-a]pyridin-1-ium chloride monohydrate, water molecules form an (8) motif parallel to the (100) plane by bonding with the chloride ions via O—H⋯Cl hydrogen bonds. The cations are connected along the b axis via N—H⋯O hydrogen bonds involving the O atoms of water molecules.

The bond lengths and angles in the molecule of the title salt are comparable with those of closely related structures detailed in Section 4 (Database survey).

Figure 2
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level.

Figure 4
View of the molecular packing along the b axis.Hydrogen bonds are depicted as in Fig. 3.

Figure 5
View of the molecular packing along the c axis.Hydrogen bonds are depicted as in Fig. 3.
The results show that the H� � �H (35.2%) contacts give the major contribution to the crystal packing, and that the C� � �H/ H� � �C (19.0%),O� � �H/H� � �O (15.5%) and F� � �H/H� � �F (9.9%) contacts also give a significant contribution to the total area of the Hirshfeld surface.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3.The N-bound H atom and the H atoms of the water molecule were located in a difference Fourier map and refined freely along with their isotropic displacement parameters.C-bound H atoms were included in calculated positions and treated as riding atoms (C-H = 0.95-0.98A ˚), with U iso (H) = 1.2U eq (C) for aromatic H atoms and 1.5U eq (C) for methyl H atoms. used to refine structure: SHELXL2019 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020).

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

Figure 1
Figure 1Reaction mechanism of the title compound.

Figure 3
Figure 3 View of the molecular packing along the a axis.N-H� � �O and O-H� � �Cl hydrogen bonds are shown as dashed lines.

Figure 6
Figure 6View of the �-� stacking interactions along the b axis in the unit cell.

Figure 7 (
Figure 7 (a) Front and (b) back sides of the three-dimensional Hirshfeld surface of the title compound mapped over d norm , with a fixed colour scale from À 0.7283 to 1.3376 a.u.
[021] by O-H� � �Cl and N-H� � �Cl hydrogen bonds.In the crystal of UREPIR, N-H� � �O interactions form a one-dimensional chain, which propagates in the b-axis direction.C-H� � �O interactions are also found in the crystal packing.The crystal structure of ABAJOE is consolidated by weak C-H� � �O and C-H� � �Cl interactions involving the 'olate' O atom and the Cl atom attached to the benzoyl group as acceptors.In the crystal of BIZWAI02, molecules are linked by O-H� � �O, N-H� � �O and C-H� � �O hydrogen bonds, and �-� interactions [centroid-to-centroid distance = 3.5822 (11) A ˚], forming a three-dimensional structure.In the crystal of UREYIA, the components are linked by N-H� � �O and C-H� � �O hydrogen bonds and �-� stacking interactions [centroidcentroid separation = 3.642 (3) A ˚].In the crystal of NEQPOP, intermolecular O-H� � �O and N-H� � �O hydrogen bonds link the molecules into two-dimensional layers.

AFigure 8
Figure 8 The two-dimensional fingerprint plots of the title compound, showing (a) all interactions, and delineated into (b) H� � �H, (c) C� � �H/H� � �C, (d) O� � �H/H� � �O and (e) F� � �H/H� � �F interactions.d e and d i represent the distances from a point on the Hirshfeld surface to the nearest atoms outside (external) and inside (internal) the surface, respectively.

Table 2
Summary of short interatomic contacts (A ˚) in the title compound.

Table 3
Experimental details.