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The title complex, 2C5H7N2+·C4H2O42−·C4H4O4, contains cyclic eight-membered hydrogen-bonded rings involving 2-­aminopyridinium and fumarate ions. The fumaric acid mol­ecules and fumarate ions lie on inversion centers and are linked into zigzag chains by O—H...O hydrogen bonds. The dihedral angle between the pyridinium ring and the hydrogen-bonded fumarate ion is 7.60 (4)°. The fumarate anion is linked to the pyridinium cations by intermolecular N—H...O hydrogen bonds. The heterocycle is fully protonated, thus enabling amine–imine tautomerization.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104010546/fr1480sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104010546/fr1480Isup2.hkl
Contains datablock I

CCDC reference: 245877

Comment top

The title complex was obtained from the reaction of 2-aminopyridine (used in the manufacture of pharmaceuticals, hair dyes and other dyes) and fumaric acid. Hydrogen bonding plays a key role in molecular recognition (Goswami & Ghosh, 1997) and crystal engineering research (Goswami et al., 1998). The design of highly specific solid-state structures is of considerable significance in organic chemistry due to their important applications in the development of new optical, magnetic and electronic systems (Lehn, 1992). The present work is part of a structural study of complexes of 2-aminopyridinium systems with hydrogen-bond donors, and we report here the structure of 2-aminopyridinium–fumarate–fumaric acid (2/1/1), (I) (Fig. 1).

The 2-aminopyridinium ions are linked to the fumarate ions through N1—H1···O4 and N2—H11···O3 hydrogen bonds, resulting in the formation of cyclic eight-membered hydrogen-bonded rings (Fig. 1 and Table 2). The 2-aminopyridinium–fumarate–fumaric acid units are arranged so that a two-dimensional network of N1—H1···O4, N2—H11···O3 and O1—H10···O4 hydrogen bonds exists and these networks are connected via N2—H12···O3 hydrogen bonds, forming a complete three-dimensional network with a dihedral angle of 79.0 (2)° between 2-aminopyridinium ions (Fig. 2).

The 2-aminopyridine–carboxylic acid system has been the subject of theoretical (Inuzuka & Fujimoto, 1990) and spectroscopic (Inuzuka & Fujimoto, 1986) amino–imino tautomerization studies. 2-Aminopyridine, like other organic bases, is protonated in acidic solutions. The bonding of the H atom to the ring N atom of 2-aminopyridine, but not to the amino N atom, gives an ion for which an additional resonance structure can be written. As this monocation has more resonance energy (additional ionic resonance) than 2-aminopyridine itself, 2-aminopyridine is a strong base, like amidines (Acheson, 1967).

The present investigation, like our previous work (Büyükgüngör & Odabaşoğlu, 2002, 2003; Odabaşoğlu et al., 2003), clearly shows that the positive charge in the 2-aminopyridinium ions of (I) is on the amino group. Our investigations show clearly that 2-aminopyridinium cation is present in the crystal lattice as the A tautomeric form (see scheme below).

The C1—N2 bond is approximately equal to a CN double-bond length (Shanmuga Sundara Raj, Fun, Lu et al., 2000), indicating that atom N2 of the amino group must also be sp2 hybridized. This is also supported by the C1—N2—H11 angle of 121.00 (13)° and by the fact that atoms C1, N2, H11 and H12 lie in the pyridine plane, with a maximum deviation of 0.018 (7) Å for atom N2 (Table 1). Similar bond distances and angles have been observed in 2-aminopyridinium succinate–succinic acid (Büyükgüngör & Odabaşoğlu, 2002) and 2-aminopyridinium adipate monoadipic acid dihydrate (Odabaşoğlu et al., 2003), bis(2-aminopyridinium)maleate (Büyükgüngör & Odabaşoğlu, 2003) and in some 2-aminopyridine-containing molecules (Yang et al., 1995; Grobelny et al., 1995; Shanmuga Sundara Raj, Fun, Zhao et al., 2000).

The CC bond length [1.311 (3) Å] in fumaric acid molecule is somewhat shorter than the CC bond length [1.319 (3) Å] of the fumarate ion. A similar bond length [1.323 (3) Å] was found in the maleate anion of previous work (Büyükgüngör & Odabaşoğlu, 2003). The average C—O distances in the carboxylate groups that form intermolecular hydrogen bonds are 1.32 (2) Å for the hydroxyl C—OH bond and 1.21 (3) Å for the carbonyl CO bond (Borthwick, 1980). The value for the carboxylate anion is also reported as 1.25 Å (Borthwick, 1980) (Table 1).

Experimental top

The title compound was prepared by mixing 2-aminopyridine and fumaric acid in a 1:1 molar ratio in water at 353 K. Crystals of (I) were obtained by slow evaporation of the solvent (m.p. 456–458 K)

Refinement top

Refined C—H distances are in the range 0.94 (2)–0.98 (2) Å and Uiso values for H atoms are in the range 0.035 (5)–0.063 (7) Å2.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. A view of the (I), with the atom-numbering scheme and 50% probability displacement ellipsoids [symmetry code: (i) −x, −y, −z]
[Figure 2] Fig. 2. A packing diagram of (I), viewed along the b axis.
2-aminopyridinium–fumarate–fumaric acid (2/1/1) top
Crystal data top
2C5H7N2+·C4H4O42·C4H2O4F(000) = 440
Mr = 420.38Dx = 1.457 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 580 reflections
a = 10.4012 (15) Åθ = 2.2–25.5°
b = 4.9254 (7) ŵ = 0.12 mm1
c = 19.162 (3) ÅT = 210 K
β = 102.484 (3)°Prism, light yellow
V = 958.5 (2) Å30.40 × 0.35 × 0.20 mm
Z = 2
Data collection top
Bruker SMART CCD area-detector
diffractometer
1868 independent reflections
Radiation source: fine-focus sealed tube1639 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.043
ω scansθmax = 26.0°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Blessing, 1995)
h = 1212
Tmin = 0.955, Tmax = 0.977k = 56
4856 measured reflectionsl = 1723
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.042Hydrogen site location: difference Fourier map
wR(F2) = 0.112All H-atom parameters refined
S = 1.08 w = 1/[σ2(Fo2) + (0.0603P)2 + 0.2244P]
where P = (Fo2 + 2Fc2)/3
1868 reflections(Δ/σ)max < 0.001
176 parametersΔρmax = 0.18 e Å3
0 restraintsΔρmin = 0.24 e Å3
Crystal data top
2C5H7N2+·C4H4O42·C4H2O4V = 958.5 (2) Å3
Mr = 420.38Z = 2
Monoclinic, P21/cMo Kα radiation
a = 10.4012 (15) ŵ = 0.12 mm1
b = 4.9254 (7) ÅT = 210 K
c = 19.162 (3) Å0.40 × 0.35 × 0.20 mm
β = 102.484 (3)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
1868 independent reflections
Absorption correction: multi-scan
(SADABS; Blessing, 1995)
1639 reflections with I > 2σ(I)
Tmin = 0.955, Tmax = 0.977Rint = 0.043
4856 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.112All H-atom parameters refined
S = 1.08Δρmax = 0.18 e Å3
1868 reflectionsΔρmin = 0.24 e Å3
176 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.28839 (11)0.9060 (2)0.48461 (6)0.0313 (3)
O20.39950 (12)0.8202 (3)0.39912 (6)0.0402 (3)
O30.01125 (10)0.6021 (2)0.37236 (5)0.0301 (3)
O40.17449 (10)0.3064 (2)0.40659 (6)0.0302 (3)
N10.24904 (12)0.3967 (3)0.27916 (7)0.0267 (3)
N20.10764 (13)0.7615 (3)0.24931 (8)0.0326 (3)
C10.19504 (14)0.5899 (3)0.23203 (8)0.0254 (3)
C20.23543 (15)0.6033 (3)0.16620 (8)0.0283 (3)
C30.32862 (15)0.4276 (3)0.15312 (8)0.0305 (4)
C40.38426 (16)0.2320 (3)0.20416 (9)0.0310 (4)
C50.34181 (15)0.2197 (3)0.26617 (9)0.0294 (4)
C60.37754 (14)0.7767 (3)0.45769 (8)0.0256 (3)
C70.45086 (15)0.5695 (3)0.50735 (8)0.0280 (3)
C80.07828 (13)0.4483 (3)0.41789 (7)0.0236 (3)
C90.04570 (14)0.4256 (3)0.49011 (8)0.0263 (3)
H10.2197 (17)0.376 (4)0.3234 (11)0.037 (5)*
H20.1965 (18)0.739 (4)0.1345 (10)0.035 (5)*
H30.3597 (17)0.441 (4)0.1088 (10)0.035 (5)*
H40.4514 (18)0.113 (4)0.1967 (10)0.037 (5)*
H50.3702 (18)0.093 (4)0.3045 (11)0.041 (5)*
H70.4234 (18)0.551 (4)0.5512 (10)0.044 (5)*
H90.0969 (17)0.291 (4)0.5218 (9)0.035 (5)*
H100.245 (2)1.048 (5)0.4535 (13)0.063 (7)*
H110.0822 (19)0.746 (4)0.2907 (11)0.039 (5)*
H120.0697 (18)0.892 (4)0.2164 (11)0.038 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0374 (6)0.0325 (6)0.0257 (6)0.0098 (5)0.0107 (4)0.0042 (5)
O20.0466 (7)0.0479 (8)0.0310 (6)0.0162 (6)0.0193 (5)0.0160 (5)
O30.0339 (6)0.0354 (6)0.0228 (5)0.0080 (5)0.0096 (4)0.0042 (5)
O40.0342 (6)0.0333 (6)0.0268 (6)0.0099 (5)0.0148 (4)0.0047 (5)
N10.0316 (7)0.0277 (7)0.0221 (6)0.0026 (5)0.0090 (5)0.0032 (5)
N20.0366 (7)0.0355 (8)0.0288 (7)0.0067 (6)0.0137 (6)0.0060 (6)
C10.0256 (7)0.0252 (8)0.0255 (7)0.0046 (6)0.0057 (6)0.0001 (6)
C20.0315 (8)0.0302 (8)0.0236 (7)0.0019 (6)0.0068 (6)0.0061 (6)
C30.0342 (8)0.0353 (9)0.0240 (8)0.0043 (7)0.0104 (6)0.0001 (7)
C40.0338 (8)0.0295 (8)0.0309 (8)0.0015 (7)0.0098 (6)0.0003 (7)
C50.0331 (8)0.0265 (8)0.0287 (8)0.0002 (6)0.0072 (6)0.0050 (7)
C60.0268 (7)0.0251 (8)0.0256 (7)0.0018 (6)0.0076 (6)0.0018 (6)
C70.0320 (8)0.0287 (8)0.0239 (7)0.0002 (6)0.0077 (6)0.0037 (6)
C80.0252 (7)0.0237 (7)0.0228 (7)0.0001 (6)0.0072 (6)0.0007 (6)
C90.0267 (7)0.0309 (8)0.0221 (7)0.0024 (6)0.0070 (6)0.0021 (6)
Geometric parameters (Å, º) top
O1—C61.3182 (18)C2—H20.94 (2)
O1—H100.97 (2)C3—C41.405 (2)
O2—C61.2118 (19)C3—H30.974 (18)
O3—C81.2482 (17)C4—C51.355 (2)
O4—C81.2771 (17)C4—H40.946 (19)
N1—C11.3479 (19)C5—H50.96 (2)
N1—C51.363 (2)C6—C71.488 (2)
N1—H10.97 (2)C7—C7i1.311 (3)
N2—C11.334 (2)C7—H70.95 (2)
N2—H110.89 (2)C8—C91.498 (2)
N2—H120.93 (2)C9—C9ii1.319 (3)
C1—C21.415 (2)C9—H90.978 (18)
C2—C31.362 (2)
C6—O1—H10112.6 (13)C5—C4—H4119.8 (11)
C1—N1—C5122.56 (13)C3—C4—H4121.7 (11)
C1—N1—H1119.8 (11)C4—C5—N1120.61 (14)
C5—N1—H1117.6 (11)C4—C5—H5126.5 (11)
C1—N2—H11121.0 (13)N1—C5—H5112.9 (11)
C1—N2—H12118.9 (12)O2—C6—O1124.50 (14)
H11—N2—H12120.0 (17)O2—C6—C7122.70 (14)
N2—C1—N1119.23 (14)O1—C6—C7112.80 (13)
N2—C1—C2122.77 (14)C7i—C7—C6122.45 (18)
N1—C1—C2117.99 (14)C7i—C7—H7122.5 (12)
C3—C2—C1119.65 (14)C6—C7—H7115.0 (12)
C3—C2—H2124.1 (11)O3—C8—O4123.61 (13)
C1—C2—H2116.2 (11)O3—C8—C9119.15 (13)
C2—C3—C4120.64 (14)O4—C8—C9117.24 (12)
C2—C3—H3120.0 (10)C9ii—C9—C8123.03 (18)
C4—C3—H3119.3 (10)C9ii—C9—H9122.0 (10)
C5—C4—C3118.52 (15)C8—C9—H9115.0 (10)
C5—N1—C1—N2177.97 (14)C3—C4—C5—N11.2 (2)
C5—N1—C1—C21.3 (2)C1—N1—C5—C40.1 (2)
N2—C1—C2—C3177.66 (15)O2—C6—C7—C7i3.9 (3)
N1—C1—C2—C31.5 (2)O1—C6—C7—C7i175.69 (19)
C1—C2—C3—C40.5 (2)O3—C8—C9—C9ii4.5 (3)
C2—C3—C4—C50.9 (2)O4—C8—C9—C9ii175.54 (18)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O40.97 (2)1.79 (2)2.7533 (16)174.2 (17)
N2—H11···O30.89 (2)2.00 (2)2.8643 (18)163.2 (19)
N2—H12···O3iii0.93 (2)2.01 (2)2.9211 (19)166.0 (17)
O1—H10···O40.97 (2)1.64 (3)2.6004 (15)175 (2)
Symmetry code: (iii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formula2C5H7N2+·C4H4O42·C4H2O4
Mr420.38
Crystal system, space groupMonoclinic, P21/c
Temperature (K)210
a, b, c (Å)10.4012 (15), 4.9254 (7), 19.162 (3)
β (°) 102.484 (3)
V3)958.5 (2)
Z2
Radiation typeMo Kα
µ (mm1)0.12
Crystal size (mm)0.40 × 0.35 × 0.20
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Blessing, 1995)
Tmin, Tmax0.955, 0.977
No. of measured, independent and
observed [I > 2σ(I)] reflections
4856, 1868, 1639
Rint0.043
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.112, 1.08
No. of reflections1868
No. of parameters176
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.18, 0.24

Computer programs: SMART (Bruker, 1997), SMART, SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).

Selected geometric parameters (Å, º) top
O1—C61.3182 (18)N1—C51.363 (2)
O2—C61.2118 (19)N2—C11.334 (2)
O3—C81.2482 (17)C7—C7i1.311 (3)
O4—C81.2771 (17)C9—C9ii1.319 (3)
N1—C11.3479 (19)
O2—C6—O1124.50 (14)O3—C8—O4123.61 (13)
C5—N1—C1—N2177.97 (14)O3—C8—C9—C9ii4.5 (3)
O2—C6—C7—C7i3.9 (3)O4—C8—C9—C9ii175.54 (18)
O1—C6—C7—C7i175.69 (19)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O40.97 (2)1.79 (2)2.7533 (16)174.2 (17)
N2—H11···O30.89 (2)2.00 (2)2.8643 (18)163.2 (19)
N2—H12···O3iii0.93 (2)2.01 (2)2.9211 (19)166.0 (17)
O1—H10···O40.97 (2)1.64 (3)2.6004 (15)175 (2)
Symmetry code: (iii) x, y+1/2, z+1/2.
 

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