3,5-Di­carboxypyridinium fluoride

The cation of the title salt, C₇H₆NO₄^+.F⁻, lies on a twofold rotation axis that passes through the N and 4-C atoms of the pyridine ring; the carb­oxy­lic acid substituent features unambiguous carbon–oxygen single and double bonds. The fluoride ion is a hydrogen-bond acceptor to two hy­droxy and one amino groups, these O—H⋯F and N—H⋯F hydrogen bonds leading to the formation of a layer structure parallel to the ab plane. The F atom lies on a position of 2 site symmetry.

Related literature

For the crystal structure of pyridine-3,5-dicarb­oxy­lic acid, see: Cowan et al. (2005); Takusagawa et al. (1973).

Experimental

Crystal data

• C₇H₆NO₄⁺·F⁻

• M_r = 187.13

• Monoclinic, C 2/c

• a = 11.3959 (14) Å

• b = 11.4503 (14) Å

• c = 6.1601 (7) Å

• β = 104.197 (2)°

• V = 779.26 (16) ų

• Z = 4

• Mo Kα radiation

• μ = 0.15 mm⁻¹

• T = 293 K

• 0.40 × 0.35 × 0.25 mm

Data collection

• Bruker SMART APEX diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996) T_min = 0.686, T_max = 0.746

• 2354 measured reflections

• 883 independent reflections

• 750 reflections with I > 2σ(I)

• R_int = 0.012

Refinement

• R[F² > 2σ(F²)] = 0.034

• wR(F²) = 0.105

• S = 1.11

• 883 reflections

• 67 parameters

• 2 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.29 e Å⁻³

• Δρ_min = −0.16 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯F1	0.86 (1)	1.60 (1)	2.458 (1)	176 (2)
N1—H2⋯F1^i	0.88 (1)	1.68 (1)	2.563 (2)	180
Symmetry code: (i) .

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Supporting information

S1. Comment

The organic salt was the crystalline product obtained in a hydrothermal reaction involving molybdic acid, hydrogen fluoride and pyridine-3,5-dicarboxylic acid; the reaction merely involved the protonation of the carboxylic acid by hydrogen fluoride. The parent carboxylic acid itself displays short O–H···O hydrogen bonds (Cowan et al., 2005; Takusagawa et al., 1973). The hydrogen fluoride salt, C₇H₆NO₄⁺ F^- (Scheme I, Fig. 1), lies on a twofold rotation axis that passes through the pyridine ring; the carboxylic acid substituent features unambiguous carbon-oxygen single- and double-bonds [1.306 (1), 1.207 (1) Å]. The fluoride ion is hydrogen bond acceptor to two hydroxy and one amino groups, these O–H···F and N–H···F hydrogen bonds leading to the formation of a layer structure parallel to the a–b plane (Fig. 2).

Related literature

For the crystal structure of pyridine-3,5-dicarboxylic acid, see: Cowan et al. (2005); Takusagawa et al. (1973).

S2. Experimental

To a solution of molybdic acid, H₂MoO₄ (1 mmol) in water (10 ml) was added 3,5-pyridinedicarboxylic acid (5 mmol). The mixture was placed in a 23 ml, Teflon-lined, stainless steel Parr bomb. Several drops of hydrofluoric acid were added. The bomb was heated at 373 for 3 days. It was then cooled to room temperature at 5 K per hour. Yellow block-shaped crystals were obtained in about 50% yield.

S3. Refinement

Carbon-bound H-atoms were placed in calculated positions (C—H 0.93 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U(C).

The amino and hydroxy H-atoms were located in a difference Fourier map, and were refined with a distance restraint of N–H 0.88±0.01 and O–H 0.84±0.01 Å; their temperature factors were freely refined.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of C7H6NO4^+ F^- at the 50% probability level; hydrogen atoms are drawn as spheres of arbitrary radius. The unlabeled atoms are related to the labeled ones by –x, y, 3/2 - z.
	Fig. 2. Layer structure.

3,5-Dicarboxypyridinium fluoride

Crystal data

C7H6NO4^+·F^−	F(000) = 384
Mr = 187.13	Dx = 1.595 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1129 reflections
a = 11.3959 (14) Å	θ = 2.6–28.4°
b = 11.4503 (14) Å	µ = 0.15 mm^−1
c = 6.1601 (7) Å	T = 293 K
β = 104.197 (2)°	Block, yellow
V = 779.26 (16) Å^3	0.40 × 0.35 × 0.25 mm
Z = 4

Data collection

Bruker SMART APEX diffractometer	883 independent reflections
Radiation source: fine-focus sealed tube	750 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.012
ω scans	θmax = 27.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −10→14
Tmin = 0.686, Tmax = 0.746	k = −13→14
2354 measured reflections	l = −8→5

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.105	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0615P)^2 + 0.1524P] where P = (Fo^2 + 2Fc^2)/3
883 reflections	(Δ/σ)max = 0.001
67 parameters	Δρmax = 0.29 e Å^−3
2 restraints	Δρmin = −0.16 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
F1	0.5000	0.54662 (9)	0.7500	0.0536 (4)
O1	0.30965 (8)	0.64863 (8)	0.74566 (19)	0.0454 (3)
H1	0.3745 (12)	0.6097 (17)	0.747 (3)	0.069 (6)*
O2	0.21589 (9)	0.47552 (8)	0.71733 (17)	0.0428 (3)
H2	0.0000	0.8997 (9)	0.7500	0.050 (6)*
N1	0.0000	0.82283 (12)	0.7500	0.0346 (4)
C1	0.21620 (10)	0.58059 (11)	0.7326 (2)	0.0321 (3)
C2	0.10381 (10)	0.64621 (10)	0.73953 (19)	0.0294 (3)
C3	0.10135 (10)	0.76662 (11)	0.7394 (2)	0.0328 (3)
H3	0.1701	0.8087	0.7320	0.039*
C4	0.0000	0.58621 (14)	0.7500	0.0294 (4)
H4	0.0000	0.5050	0.7500	0.035*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0272 (6)	0.0273 (6)	0.1130 (11)	0.000	0.0301 (6)	0.000
O1	0.0245 (5)	0.0335 (5)	0.0811 (7)	0.0017 (4)	0.0183 (5)	−0.0042 (5)
O2	0.0370 (6)	0.0281 (5)	0.0663 (7)	0.0059 (4)	0.0184 (5)	−0.0033 (4)
N1	0.0268 (7)	0.0209 (7)	0.0570 (9)	0.000	0.0121 (6)	0.000
C1	0.0265 (6)	0.0299 (6)	0.0409 (7)	0.0029 (5)	0.0102 (5)	−0.0008 (5)
C2	0.0249 (6)	0.0254 (6)	0.0385 (6)	0.0012 (4)	0.0087 (5)	−0.0012 (4)
C3	0.0239 (6)	0.0260 (6)	0.0495 (7)	−0.0025 (4)	0.0108 (5)	−0.0004 (5)
C4	0.0272 (8)	0.0218 (7)	0.0394 (9)	0.000	0.0085 (6)	0.000

Geometric parameters (Å, º)

O1—C1	1.306 (1)	C1—C2	1.495 (2)
O1—H1	0.86 (1)	C2—C3	1.379 (2)
O2—C1	1.207 (2)	C2—C4	1.383 (1)
N1—C3^i	1.338 (1)	C3—H3	0.9300
N1—C3	1.338 (1)	C4—C2^i	1.383 (1)
N1—H2	0.88 (1)	C4—H4	0.9300
C1—O1—H1	112.1 (14)	C3—C2—C1	121.33 (11)
C3^i—N1—C3	122.48 (15)	C4—C2—C1	120.03 (11)
C3^i—N1—H2	118.76 (7)	N1—C3—C2	119.92 (11)
C3—N1—H2	118.76 (7)	N1—C3—H3	120.0
O2—C1—O1	125.90 (11)	C2—C3—H3	120.0
O2—C1—C2	121.15 (11)	C2—C4—C2^i	120.44 (15)
O1—C1—C2	112.95 (11)	C2—C4—H4	119.8
C3—C2—C4	118.62 (11)	C2^i—C4—H4	119.8
O2—C1—C2—C3	−174.90 (12)	C4—C2—C3—N1	0.20 (16)
O1—C1—C2—C3	5.39 (16)	C1—C2—C3—N1	−178.73 (9)
O2—C1—C2—C4	6.18 (17)	C3—C2—C4—C2^i	−0.10 (8)
O1—C1—C2—C4	−173.53 (9)	C1—C2—C4—C2^i	178.85 (11)
C3^i—N1—C3—C2	−0.10 (8)

Symmetry code: (i) −x, y, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···F1	0.86 (1)	1.60 (1)	2.458 (1)	176 (2)
N1—H2···F1^ii	0.88 (1)	1.68 (1)	2.563 (2)	180

Symmetry code: (ii) x−1/2, y+1/2, z.