Pyridin-4-ylmethanaminium perchlorate monohydrate

The title compound crystallizes in the monoclinic space group P21/n with two formula units per asymmetric unit (Z′ = 2) and features an intricate tri-periodic hydrogen-bonding network.


data reports
13.2 (3) in molecule 2. The difference is ascribable to intermolecular interactions and packing effects in the solid state. In the nine crystal structures containing 4-picolylammonium ions deposited with the CSD, the torsion angles range from 6.4 in HEBJOR to 88.5 in WEBXAE, indicating great conformational flexibility. The molecular structure of cation 2 in (1) exhibits an r.m.s. deviation from C S point group symmetry of 0.082 Å , as calculated with MOLSYM in PLATON (Spek, 2020). The two crystallographically distinct perchlorate anions are non-disordered, both showing an r.m.s. deviation of 0.011 Å from molecular T d point group symmetry.
Apart from Coulombic interactions, the supramolecular structure in (1) is dominated by classical N-HÁ Á ÁO, O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds. Fig. 2 depicts a part of the crystal structure, illustrating the crystallographically unique hydrogen bonds. As hydrogen-bond donors, the water molecules join the 4-picolylammonium and perchlorate ions through O-HÁ Á ÁN pyridine and O-HÁ Á ÁO hydrogen bonds, respectively. Towards the protonated amino groups, the water molecules act as hydrogen-bond acceptors for N-HÁ Á ÁO hydrogen bonds, resulting in hydrogen-bonded chains propagating parallel to the c-axis direction. The remaining hydrogen-bond donor sites of the 4-picolylammonium ions form donating bifurcated N-HÁ Á ÁO hydrogen bonds to perchlorate oxygen atoms, resulting in an intricate tri-periodic network. Table 1 lists numerical details of the relevant hydrogen bonds in (1), which are characteristic of strong hydrogen bonds (Thakuria et al., 2017).

Synthesis and crystallization
Compound (1) was synthesized by adding a solution of 4picolylamine (216 mg, 2 mmol) in 40 ml of ethanol to 40 ml of 0.1 M perchloric acid. The reaction mixture was stirred for 4 h at room temperature and then left at ambient conditions. After one week, the precipitate was collected by filtration and air-dried. Colourless crystals of (1) suitable for X-ray diffraction were grown from a methanol/water solution at room temperature over a period of three weeks, while the solvents were allowed to evaporate slowly. Caution: organic perchlorate salts are potentially explosive and should be handled with care!

Refinement
Crystal data, data collection and structure refinement details are listed in Table 2. Part of the crystal structure of (1) viewed approximately along the a-axis direction towards the origin, showing N-HÁ Á ÁO, O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds (dashed lines). The number after the underscore indicates unique molecules 1 and 2 in each case. Carbon-bound hydrogen atoms are omitted for clarity. Symmetry codes refer to Table 1. Table 1 Hydrogen-bond geometry (Å , ).

Figure 1
Asymmetric unit of (1

data-1
IUCrData ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.44 e Å −3 Δρ min = −0.42 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.

data-2
IUCrData (2023). 8, x230459 Refinement. Nitrogen-bound and water hydrogen atoms were located from difference-Fourier maps and were refined with N-H and O-H distances restrained to target values of 0.91 (2) and 0.84 (2) Å, respectively. The respective U iso (H) values were refined freely.