2,4,6-Trimethyl­pyridinium dihydrogen phosphate

Jing Dai; Jie Xu

doi:10.1107/S1600536810052153

. 2010 Dec 18;67(Pt 1):o149. doi: 10.1107/S1600536810052153

2,4,6-Trimethylpyridinium dihydrogen phosphate

Jing Dai ^a,^*, Jie Xu ^a

PMCID: PMC3050353 PMID: 21522656

Abstract

The asymmetric unit of the title compound, C₈H₁₂N⁺·H₂PO₄ ⁻, contains two H₂PO₄ ⁻ anions and two 2,4,6-trimethylpyridinium cations. In the crystal, the anions are linked by O—H⋯O hydrogen bonds, forming supramolecular chains running along the a axis; the cations are connected to the anion chains by N—H⋯O hydrogen bonds. Weak intermolecular C—H⋯O hydrogen bonding is also present in the crystal structure.

Related literature

For the properties and structures of pyridine salts, see: Fu et al. (2007 ▶, 2008 ▶, 2009 ▶); Fu & Xiong (2008 ▶).

Experimental

Crystal data

C₈H₁₂N⁺·H₂PO₄ ⁻
M _r = 219.17
Monoclinic,
a = 7.9501 (16) Å
b = 15.324 (3) Å
c = 9.0252 (18) Å
β = 97.97 (3)°
V = 1088.9 (4) Å³
Z = 4
Mo Kα radiation
μ = 0.24 mm⁻¹
T = 298 K
0.30 × 0.05 × 0.05 mm

Data collection

Rigaku Mercury2 diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T _min = 0.910, T _max = 1.000
11306 measured reflections
4970 independent reflections
3973 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.101
S = 1.02
4970 reflections
275 parameters
5 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.15 e Å⁻³
Δρ_min = −0.25 e Å⁻³
Absolute structure: Flack (1983 ▶), 2380 Friedel pairs
Flack parameter: 0.01 (8)

Data collection: CrystalClear (Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810052153/xu5121sup1.cif

e-67-0o149-sup1.cif^{(20.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810052153/xu5121Isup2.hkl

e-67-0o149-Isup2.hkl^{(243.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O8	0.85 (2)	1.77 (2)	2.610 (2)	169 (3)
O3—H3⋯O7ⁱ	0.85 (3)	1.72 (3)	2.569 (2)	173 (3)
O5—H5⋯O4ⁱⁱ	0.84 (2)	1.79 (2)	2.627 (3)	173 (3)
O6—H6⋯O2	0.85 (2)	1.69 (2)	2.538 (2)	176 (3)
N1—H1A⋯O4ⁱⁱⁱ	0.86	1.77	2.633 (3)	177
N2—H2A⋯O8^iv	0.86	1.78	2.632 (3)	170
C2—H2B⋯O6^v	0.93	2.59	3.443 (4)	152
C4—H4A⋯O7ⁱ	0.93	2.59	3.481 (4)	161

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

This work was supported by a start-up grant from Southeast University, China.

supplementary crystallographic information

Comment

Salts of pyridine attracted more attention as phase transition dielectric materials for its application in memory storage (Fu et al. 2007; Fu & Xiong 2008; Fu et al. 2008; Fu et al. 2009). With the purpose of obtaining phase transition crystals of 2,4,6-trimethylpyridine salts, its interaction with various acids has been studied and we have elaborated a series of new materials with this organic molecule. In this study, we describe the crystal structure of the title compound, di-2,4,6-trimethylpyridinium dihydrogen phosphate.

The dielectric constant of title compound as a function of temperature indicates that the permittivity is basically temperature-independent, suggesting that this compound should be not a real ferroelectrics or there may be no distinct phase transition occurred within the measured temperature range. Similarly, below the melting point (425 K) of the compound, the dielectric constant as a function of temperature also goes smoothly, and there is no dielectric anomaly observed (dielectric constant equaling to 6.9 to 8.7).

The asymmetric unit is composed of two H₂PO₄^- anion and two C₈H₁₂N⁺ cation (Fig.1). Both the pyridine N atoms are protonated, thus indicating two positive charges in the pyridine N atoms. And the H₂PO₄^- anions were showing two negative charges to make the charge balance. The geometric parameters of the title compound are in the normal range.

In the crystal structure, all the H atoms of pyridinium cations and the H₂PO₄^- anions are involved in N—H···O and O—H···O hydrogen bonds. These hydrogen bonds link the ionic units into a one-dimentional chains parallel to the a-axis. Furthermore, the π···π (centroid-to-centroid distance = 3.8403 (8) Å and 4.1676 (8) Å) interactions link the chains into a two-dimentional network parallel to the (0 0 1) plane. (Table 1 and Fig.2).

Experimental

The commercial 2,4,6-trimethylpyridine (3 mmol) was dissolved in water/H₃PO₄ (50:1 v/v) solution. The solvent was slowly evaporated in air affording colourless needle-shaped crystals of the title compound suitable for X-ray analysis.