3-(Ammoniomethyl)pyridinium bis(perchlorate)

In the title molecular salt, C6H10N2 2+·2ClO4 −, the Cl—O bond lengths [anion 1: 1.369 (3)–1.415 (3); anion 2: 1.420 (2)–1.441 (2) Å] and the O—Cl—O angles [anion 1: 105.4 (2)–111.8 (4); anion 2: 107.8 (1)–110.3 (1)°] indicate a slight distortion of the perchlorate anions from regular tetrahedral symmetry. In the crystal, the components are linked into columns along the a-axis direction via N—H⋯O and C—H⋯O hydrogen bonds, with stacks of the organic molecules being surrounded by stacks of perchlorate anions.

The structure consists of one 3-ammoniomethylpyrinidinium dication and two perchlorate anions (Fig. 1). In the crystal, the three H atoms of the ammonium group are involved into N-H···Cl and N-H···O hydrogen bonds: N2-H2C···Cl1(v), N2-H2B···Cl2(ii), N2-H2C···O1(v), N2-H2A··· (O6vi, O2iv) and N2-H2B··· (O6iv, O3vii), the two laters are bifurcated (for the symmetry codes, see Table 1). These hydrogen bonds link the ionic units (NH 3 + and [ClO 4 ] -) to form columns running along the a-axis direction (Fig.2) and situated at y = z = 1/2 (Fig.3). The organic groups are located between these columns via two kinds of hydrogen bonds: a bifurcated N-H···O and two C-H···O: N1-H1 (O5, O7viii), C6-H6A···O8(iii) and C5-H5···O1(vi) (Fig. 3, Table 1). No π-π stacking interactions between the organic rings or C-H··· π interactions towards them are observed. It is worth noting that the C-N-C angles of pyridine are very sensitive to protonation: a pyridinium cation always has an expanded angle of the C-N-C in comparison with the parent pydidine. The angle C(5)-N(1)-C(1) [123.4 (2)°] is consistent with the type of pyridinium cation. The hydrogen atom HN(1), which is deprived from its parent, attaches the nitrogen atom. As expected, the [ClO 4 ]anion has typical tetrahedral geometry where the Cl-O bond lengths and O-Cl-O angles are not equal to one another but vary with the environment around the O atoms. In the title compound, the Cl-O bond lengths vary from 1.369 (3) (Kapplinger & Keutel, 1999). The O-Cl-O angles range from 105.4 (2) to 111.8 (4)° for the first anion and from 109.04 (15) to 110.33 (13)° for the second one. These values, which are characteristic of perchlorate anions (Ye et al., 2002), clearly indicate that the coordination geometry of the Cl(2) atom can be regarded as being a less distorted tetrahedron than the one of the Cl(1). However, for the Cl(2)O 4 tetrahedron, all the oxygen atoms are involved in hydrogen bonds, while only three oxygen atoms act as acceptors of hydrogen bonds for the [Cl(1)O 4 ] tetrahedron.
Experimental 3-ammoniomethylpyrinidinium (1 mmol, 0.108 g) was dissolved in a mixture of distilled water (10 ml) and perchloric acid (0.5 ml).The resultant solution was evaporated at room temperature. Crystals of the title compound, which remained stable under normal conditions of temperature and humidity, were isolated after several days and subjected to X-ray diffraction analysis (yield 64%).

Refinement
All the H-atoms were located in difference Fourier synthesis maps and refined as riding on their parent atoms, using SHELXL97 (Sheldrick, 2008) defaults.

Figure 1
A view of the title compound, showing 50% probability displacement ellipsoids and arbitrary spheres for the H atoms.   The crystal packing of the title compound viewed along the a axis.

3-(Ammoniomethyl)pyridinium bis(perchlorate)
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.