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Two cyclic eight-membered hydrogen-bonded rings exist in the title compound, 2C5H7N2+·C4H2O42−, involving the 2-amino­pyridinium and maleate ions. The dihedral angle between the two pyridinium rings hydrogen bonded to the maleate ion is 74.80 (4)°. The maleate anion lies on a twofold axis and is linked to the pyridinium cations by intermolecular N—H...O hydrogen bonds. The heterocycle is fully proton­ated, which enables amino–imino tautomerization.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103001586/fr1408sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103001586/fr1408Isup2.hkl
Contains datablock I

CCDC reference: 208007

Comment top

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 bis(2-aminopyridinium) maleate, (I). A similar series of complexes formed from 2-aminopyridine and carboxylate have been reported recently (Büyükgüngör & Odabaşoǧlu, 2002; Odabaşoǧlu et al., 2003). \sch

A view of hydrogen-bonded (I) is shown in Fig. 1. The complex owes its formation to two hydrogen-bond pairs, one between atoms O1 and O2 of the maleate ions and hydrogen-bond donors N1—H1 and N2—H2A, and the other between their symmetry-related pairs. There are two eight-membered rings in the structure, formed as a result of these N—H···O hydrogen-bonds. Furthermore, there is also an intermolecular hydrogen-bond in (I) (Table 2).

The average C—O distances of carboxylate groups that form intermolecular hydrogen bonds are 1.32 (2) Å for the hydroxyl C—OH and 1.21 (3) Å for the carbonyl CO bond (Borthwick, 1980). This value for the carboxylate anion is also reported as 1.25 Å (Borthwick, 1980). The bond lengths of O1—C11 and O2—C11 in (I) thus fall into the category of a normal COO group (Table 1).

The C—N—C angle of pyridines is very sensitive to protonation (Jin, Pan, Xu & Xu, 2000 Is this the correct citation?; Jin et al., 2002). In comparison with 2-amino-6-methylpyridinium neoabietate (Jin, Pan, Liu & Xu, 2000), the complete protonation of the heterocycle in (I) is indicated by the enlarged C1—N1—C5 angle [122.69 (15)°] and by the reduced N1—C1—C2 angle [117.47 (16)°]. The 2-aminopyridine-carboxylic acid system has been the subject of theoretical (Inuzuka & Fujimoto, 1990) and spectroscopic (Inuzuka & Fujimoto, 1986) amino-imino tautomerization studies. The main features of amino-imino tautomerization (Scheme 2) are shown in the structure of (I) by the bond lengths and angles of the heterocycle and the maleate anion, respectively. The present investigation, like our previous work (Büyükgüngör & Odabaşoǧlu, 2002; Odabaşoǧlu et al., 2003), clearly shows that the positive charge in the 2-aminopyridinium ions of (I) is on the amino group.

Experimental top

The title compound was prepared by dissolving 2-aminopyridine and maleic acid in a 2:1 molar ratio in water at 373 K, and crystals of (I) were obtained by slow evaporation of the solvent at the room temperature.

Refinement top

Although space group Cc gave a chemically reasonable and computationally stable refinement, the correct space group was found to be Fdd2. Refinement of the absolute structure parameter was meaningless because of its large s.u. (1.2), and so Friedel-pair reflections were averaged before the final refinement. All the H atoms were treated using a riding model, with C—H distances of 0.95 Å and N—H distances of 0.88 Å, and with Uiso(H) = 1.2Ueq(parent).

Computing details top

Data collection: XSCANS (Siemens 1991); cell refinement: XSCANS; data reduction: SHELXTL (Sheldrick, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1998).

Figures top
[Figure 1] Fig. 1. A view of the moieties of (I), with the atom-numbering scheme and 50% probability displacement ellipsoids [symmetry code: (i) 1/2 − x, 1/2 − y, z].
[Figure 2] Fig. 2. A packing diagram for (I), viewed along the c axis.
Bis(2-aminopyridinium) maleate top
Crystal data top
2C5H7N2+·C4H2O42Dx = 1.403 Mg m3
Mr = 304.30Melting point = 415–418 K
Orthorhombic, Fdd2Mo Kα radiation, λ = 0.71073 Å
Hall symbol: F 2 -2dCell parameters from 161 reflections
a = 21.756 (5) Åθ = 2.6–12.7°
b = 23.531 (5) ŵ = 0.11 mm1
c = 5.6280 (11) ÅT = 153 K
V = 2881.2 (11) Å3Rectangular, light yellow
Z = 80.20 × 0.15 × 0.10 mm
F(000) = 1280
Data collection top
Siemens P4
diffractometer
Rint = 0.016
Radiation source: fine-focus sealed tubeθmax = 27.0°, θmin = 2.5°
Graphite monochromatorh = 275
ω scansk = 300
1564 measured reflectionsl = 67
873 independent reflections1 standard reflections every 120 min
814 reflections with I > 2σ(I) intensity decay: <2%
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.026H-atom parameters constrained
wR(F2) = 0.072 w = 1/[σ2(Fo2) + (0.0451P)2 + 0.5722P]
where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max < 0.001
873 reflectionsΔρmax = 0.11 e Å3
101 parametersΔρmin = 0.11 e Å3
1 restraintExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0048 (6)
Crystal data top
2C5H7N2+·C4H2O42V = 2881.2 (11) Å3
Mr = 304.30Z = 8
Orthorhombic, Fdd2Mo Kα radiation
a = 21.756 (5) ŵ = 0.11 mm1
b = 23.531 (5) ÅT = 153 K
c = 5.6280 (11) Å0.20 × 0.15 × 0.10 mm
Data collection top
Siemens P4
diffractometer
Rint = 0.016
1564 measured reflections1 standard reflections every 120 min
873 independent reflections intensity decay: <2%
814 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0261 restraint
wR(F2) = 0.072H-atom parameters constrained
S = 1.05Δρmax = 0.11 e Å3
873 reflectionsΔρmin = 0.11 e Å3
101 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
N10.20760 (6)0.10405 (5)0.4447 (3)0.0369 (3)
H10.21840.12790.55760.044*
N20.10908 (7)0.10719 (7)0.5886 (3)0.0537 (4)
H2A0.12120.13160.69730.064*
H2B0.07040.09630.58350.064*
C10.14878 (7)0.08687 (6)0.4336 (3)0.0378 (4)
C20.13296 (8)0.04786 (8)0.2529 (4)0.0462 (4)
H20.09210.03400.24230.055*
C30.17568 (9)0.03024 (8)0.0951 (4)0.0501 (5)
H30.16440.00470.02810.060*
C40.23675 (9)0.04951 (7)0.1121 (4)0.0495 (4)
H40.26710.03720.00240.059*
C50.25099 (8)0.08613 (7)0.2892 (4)0.0421 (4)
H50.29200.09950.30470.051*
O10.23854 (5)0.18379 (5)0.7565 (2)0.0413 (3)
O20.14697 (6)0.18946 (6)0.9268 (3)0.0608 (4)
C110.20258 (7)0.19907 (6)0.9210 (3)0.0354 (3)
C120.22988 (7)0.22893 (6)1.1315 (3)0.0355 (3)
H120.21670.21601.28300.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0367 (7)0.0372 (6)0.0367 (7)0.0039 (5)0.0012 (6)0.0028 (6)
N20.0367 (7)0.0697 (10)0.0547 (10)0.0103 (7)0.0071 (7)0.0200 (8)
C10.0359 (7)0.0393 (7)0.0381 (9)0.0021 (6)0.0011 (7)0.0018 (7)
C20.0414 (9)0.0490 (9)0.0483 (10)0.0053 (7)0.0065 (8)0.0074 (8)
C30.0594 (11)0.0470 (9)0.0438 (10)0.0010 (8)0.0061 (9)0.0102 (8)
C40.0523 (10)0.0504 (9)0.0458 (10)0.0050 (8)0.0103 (9)0.0047 (9)
C50.0376 (8)0.0420 (8)0.0467 (9)0.0013 (6)0.0056 (7)0.0027 (7)
O10.0346 (5)0.0495 (6)0.0398 (6)0.0036 (5)0.0037 (5)0.0124 (6)
O20.0356 (6)0.0793 (9)0.0675 (9)0.0087 (6)0.0103 (6)0.0273 (8)
C110.0335 (7)0.0336 (7)0.0392 (8)0.0001 (6)0.0041 (7)0.0021 (6)
C120.0426 (8)0.0348 (6)0.0291 (7)0.0038 (6)0.0032 (7)0.0015 (7)
Geometric parameters (Å, º) top
N1—C11.3434 (19)C3—H30.9500
N1—C51.354 (2)C4—C51.354 (3)
N1—H10.8800C4—H40.9500
N2—C11.318 (2)C5—H50.9500
N2—H2A0.8800O1—C111.264 (2)
N2—H2B0.8800O2—C111.2310 (19)
C1—C21.412 (3)C11—C121.500 (2)
C2—C31.351 (3)C12—C12i1.323 (3)
C2—H20.9500C12—H120.9500
C3—C41.407 (3)
C1—N1—C5122.69 (15)C4—C3—H3119.8
C1—N1—H1118.7C5—C4—C3118.12 (17)
C5—N1—H1118.7C5—C4—H4120.9
C1—N2—H2A120.0C3—C4—H4120.9
C1—N2—H2B120.0C4—C5—N1120.96 (16)
H2A—N2—H2B120.0C4—C5—H5119.5
N2—C1—N1118.97 (16)N1—C5—H5119.5
N2—C1—C2123.56 (15)O2—C11—O1125.12 (16)
N1—C1—C2117.47 (16)O2—C11—C12117.01 (15)
C3—C2—C1120.34 (16)O1—C11—C12117.81 (13)
C3—C2—H2119.8C12i—C12—C11127.83 (8)
C1—C2—H2119.8C12i—C12—H12116.1
C2—C3—C4120.40 (17)C11—C12—H12116.1
C2—C3—H3119.8
C5—N1—C1—N2178.63 (16)C2—C3—C4—C50.4 (3)
C5—N1—C1—C21.0 (3)C3—C4—C5—N10.5 (3)
N2—C1—C2—C3177.82 (18)C1—N1—C5—C40.1 (3)
N1—C1—C2—C31.8 (3)O2—C11—C12—C12i136.4 (2)
C1—C2—C3—C41.5 (3)O1—C11—C12—C12i46.3 (3)
Symmetry code: (i) x+1/2, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.881.782.6557 (18)172
N2—H2A···O20.881.962.837 (2)177
N2—H2B···O1ii0.881.972.832 (2)168
Symmetry code: (ii) x1/4, y+1/4, z1/4.

Experimental details

Crystal data
Chemical formula2C5H7N2+·C4H2O42
Mr304.30
Crystal system, space groupOrthorhombic, Fdd2
Temperature (K)153
a, b, c (Å)21.756 (5), 23.531 (5), 5.6280 (11)
V3)2881.2 (11)
Z8
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.20 × 0.15 × 0.10
Data collection
DiffractometerSiemens P4
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
1564, 873, 814
Rint0.016
(sin θ/λ)max1)0.639
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.026, 0.072, 1.05
No. of reflections873
No. of parameters101
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.11, 0.11

Computer programs: XSCANS (Siemens 1991), XSCANS, SHELXTL (Sheldrick, 1990), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1998).

Selected geometric parameters (Å, º) top
N1—C11.3434 (19)O1—C111.264 (2)
N1—C51.354 (2)O2—C111.2310 (19)
N1—H10.8800C11—C121.500 (2)
N2—C11.318 (2)C12—C12i1.323 (3)
C1—C21.412 (3)
C1—N1—C5122.69 (15)N1—C1—C2117.47 (16)
Symmetry code: (i) x+1/2, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.881.782.6557 (18)172
N2—H2A···O20.881.962.837 (2)177
N2—H2B···O1ii0.881.972.832 (2)168
Symmetry code: (ii) x1/4, y+1/4, z1/4.
 

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