4-Carb­oxy­pyridin-1-ium 2,4,5-tri­carb­oxy­benzoate monohydrate

Hadi D Arman; Edward R T Tiekink

doi:10.1107/S1600536813016437

. 2013 Jun 19;69(Pt 7):o1122–o1123. doi: 10.1107/S1600536813016437

4-Carboxypyridin-1-ium 2,4,5-tricarboxybenzoate monohydrate

Hadi D Arman ^a, Edward R T Tiekink ^b,^*

PMCID: PMC3770392 PMID: 24046677

Abstract

The title hydrated salt, C₆H₆NO₂ ⁺·C₁₀H₅O₈ ⁻·H₂O, was isolated from the 1:1 cocrystallization of benzene-1,2,4,5-tetracarboxylic acid and isonicotinic acid in ethanol solution. In the crystal, the cation is close to planar [r.m.s. deviation = 0.085 Å for the nine fitted atoms; the C—C—C—O(carbonyl) torsion angle = −8.7 (4)°], but twists are evident in the anion, with all but the carboxylic acid group diagonally opposite the carboxylate group being significantly twisted out of the plane of the benzene ring [C—C—C—O(carbonyl) torsion angles = −118.1 (2), −157.6 (2), 4.3 (3) and 77.3 (3)°]. In the crystal, the ions and water molecules are consolidated into a three-dimensional architecture by O—H⋯O and N—H⋯O hydrogen bonding along with C—H⋯O interactions.

Related literature

For background to pharmaceutical co-crystals, see: Almarsson & Zaworotko (2004 ▶). For related co-crystallization studies on 1,2,4,5-benzenetetracarboxylic acid, see: Arman & Tiekink (2013a ▶,b ▶). For the structure of isonicotinic acid, see: Takusagawa & Shimada (1976 ▶). For the structure of the analogous salt formed from nicotinic acid, see: Dos Santos et al. (2012 ▶). For the calculation of pK _a values, see: Chemaxon (2009 ▶).

Experimental

Crystal data

C₆H₆NO₂ ⁺·C₁₀H₅O₈ ⁻·H₂O
M _r = 395.27
Triclinic,
a = 9.724 (2) Å
b = 10.007 (2) Å
c = 10.755 (2) Å
α = 99.56 (1)°
β = 114.667 (8)°
γ = 110.283 (9)°
V = 830.7 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.14 mm⁻¹
T = 98 K
0.33 × 0.25 × 0.20 mm

Data collection

Rigaku AFC12/SATURN724 diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.807, T _max = 1.000
5233 measured reflections
3414 independent reflections
3200 reflections with I > 2σ(I)
R _int = 0.020

Refinement

R[F ² > 2σ(F ²)] = 0.056
wR(F ²) = 0.133
S = 1.17
3414 reflections
281 parameters
8 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012 ▶) and DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536813016437/hb7093sup1.cif

e-69-o1122-sup1.cif^{(19.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813016437/hb7093Isup2.hkl

e-69-o1122-Isup2.hkl^{(164KB, hkl)}

Click here for additional data file.^{(6.5KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536813016437/hb7093Isup3.cml

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
O4—H4O⋯O3ⁱ	0.84 (3)	1.82 (3)	2.654 (3)	176 (3)
O6—H6O⋯O1ⁱⁱ	0.85 (5)	1.69 (5)	2.534 (3)	174 (5)
O8—H8O⋯O1W	0.85 (5)	1.79 (5)	2.634 (3)	171 (6)
O10—H10O⋯O2ⁱⁱⁱ	0.85 (4)	1.78 (4)	2.625 (3)	172 (4)
N1—H1N⋯O5^iv	0.89 (4)	1.86 (4)	2.711 (3)	160 (4)
O1W—H1W⋯O2^v	0.85 (2)	2.16 (2)	2.957 (3)	156 (3)
O1W—H2W⋯O2ⁱⁱⁱ	0.85 (1)	2.05 (2)	2.853 (3)	158 (4)
C6—H6⋯O7^v	0.95	2.40	3.267 (3)	151
C12—H12⋯O9^vi	0.95	2.35	3.179 (4)	146
C14—H14⋯O6^vii	0.95	2.40	3.300 (4)	159

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

Acknowledgments

We gratefully thank the Ministry of Higher Education (Malaysia) for funding structural studies through the High-Impact Research scheme (UM.C/HIR-MOHE/SC/12).

supplementary crystallographic information

Comment

Interest in co-crystallization experiments stems largely from potential applications in the pharmaceutical industry (Almarsson & Zaworotko, 2004). The title salt hydrate, (I), was isolated during an investigation of co-crystallization experiments with 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid; LH₄) and various pyridyl derivatives (Arman & Tiekink, 2013a; Arman & Tiekink, 2013b).

The 1:1 co-crystallization of pyromellitic acid and isonicotinic acid in an ethanol solution afforded a salt hydrate, (I), there being one complete molecule of the 4-carboxypyridin-1-ium cation, the hydroxy(2,4,5-tricarboxyphenyl)methanolate anion and a water molecule in the asymmetric unit. Confirmation of protonation of isonicotinic acid during crystallization is found in the nature of hydrogen bonding involving the pyridinium cation (see below), and the widening of the C13—N1—C14 angle to 123.1 (2)° cf. 118.9 (2)° in the structure of isonicotinic acid itself (Takusagawa & Shimada, 1976). Further, the disparity in the C—O bond lengths of the carboxylic acid residue, Δ(C—O) = [(C—O)_long - (C—O)_short] = 0.10 Å, confirms that isonicotinic acid has been protonated at N1, rather than existing in a zwitterionic form, with equivalent C—O bonds. Complementing this evidence, in the anion, the Δ(C—O) value for the O1-carboxylate group is 0.01 Å, indicating considerable delocalization of electron density over the CO₂ atoms, compared to values in the range 0.07 to 0.11 Å for the remaining carboxylic acids.

In the cation, the carboxylic acid residue is approximately co-planar with the pyridyl ring to which it is attached as seen in the C12—C11—C16—O9 torsion angle of -8.7 (4)°. Indeed, the entire cation is approximately planar with the r.m.s. deviation = 0.085 Å for the nine fitted atoms. By contrast, anion is non-planar with the carboxylic acid diagonally opposite the carboxylate group being co-planar to the phenyl ring [C—C—C—O(carbonyl) torsion angle = 4.3 (3)°] but the remaining carboxylic acids and carboxylate residues deviate significantly [C—C—C—O(carbonyl) torsion angles =-118.1 (2), -157.6 (2) and 77.3 (3)°].

The three-dimensional crystal structure of (I) is consolidated by O—H···O and N—H···O hydrogen bonding involving all three components of the structure; geometric parameters characterizing these are summarized in Table 1. Two distinct supramolecular aggregation patterns are clearly discerned, with the first of these being a tape along [1 0 0] comprising hydroxy(2,4,5-tricarboxyphenyl)methanolate anions, Fig. 2, which is sustained by centrosymmetric eight-membered {···O=COH}₂ synthons involving the O3-carboxylic acid and orthogonal O6—H···O1 hydrogen bonds. A supramolecular chain containing alternating cations and anions is also found, Fig. 3. This is aligned along [1 0 - 1] and is stabilized by O10—H···O2 and N1—H···O5 hydrogen bonds. The aforementioned are connected into a supramolecular layer in the ac plane. As seen in Fig. 4, the centrosymmetrically related water molecules are bridged by carboxylate-O2 atoms to form an eight-membered {···HOH···O}₂ ring. The water-O1w atom also accepts a hydrogen bond from the O8—H hydroxyl group. Also evident from the image in Fig. 4 is the critical role played by the trifurcated carboxylate-O2 atom in stabilizing the crystal structure. Several of the oxygen atoms not involved in formal hydrogen bonding interactions participate in C—H···O interactions to consolidate the crystal packing, Fig. 5.

While salt (I) was characterized from the 1:1 co-crystallization of LH₄ with isonicoinic acid in an ethanol solution, the analogous experiment with nicotinic [NA] acid gave a salt of composition [NAH]₂[LH₂] (Dos Santos, et al., 2012). While protonation of NA is not surprising the fact that LH₄ has been doubly deprotonated correlates nicely with the increased basicity of the nitrogen atom in NA cf. isonicotinic acid, i.e. calculated pK_a = 4.19 and 2.35, respectively (Chemaxon, 2009).

Experimental

Crystals of the title salt hydrate were harvested from an ethanol (10 ml) solution containing a 1:1 molar ratio of pyromellitic acid (Sigma-Aldrich; 6 mg) and isonicoinic acid (Sigma-Aldrich; 3 mg).