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Acta Crystallogr Sect E Struct Rep Online. 2009 January 1; 65(Pt 1): o22.
Published online 2008 December 6. doi:  10.1107/S1600536808040221
PMCID: PMC2967941

4-Carb­oxy-2-methyl-1H-imidazol-3-ium-5-carboxyl­ate monohydrate

Abstract

In the title compound, C6H6N2O4·H2O, one carboxyl group is deprotonated and one imidazole N atom is protonated. The organic mol­ecule, excluding methyl H atoms, is essentially planar, with an r.m.s. deviation of 0.0156 (1) Å. In the crystal structure, inter­molecular N—H(...)O hydrogen bonds link mol­ecules into chains along the b axis; these chains are further linked via O—H(...)O hydrogen bonds involving the water O atoms and carboxyl O atoms, generating a two-dimensional supra­molecular framework.

Related literature

For details of related structures, see: Sun et al. (2006 [triangle]); Nie et al. (2007 [triangle]). For applications as functional materials, see: Liang et al. (2002 [triangle]); Qin et al. (2002 [triangle]); Li et al. (1998 [triangle]). For biological activities, see: Ucucu et al. (2001 [triangle]); Maeda et al. (1984 [triangle]); Quattara et al. (1987 [triangle]); Seko et al. (1991 [triangle]). For the synthesis of the title compound, see: Anderson et al. (1989 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-00o22-scheme1.jpg

Experimental

Crystal data

  • C6H6N2O4·H2O
  • M r = 188.14
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-00o22-efi1.jpg
  • a = 8.491 (2) Å
  • b = 14.280 (4) Å
  • c = 6.5385 (17) Å
  • β = 97.386 (5)°
  • V = 786.2 (4) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.14 mm−1
  • T = 295 (2) K
  • 0.23 × 0.09 × 0.08 mm

Data collection

  • Bruker SMART APEX area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996 [triangle]) T min = 0.969, T max = 0.995
  • 4506 measured reflections
  • 1538 independent reflections
  • 1246 reflections with I > 2σ(I)
  • R int = 0.032

Refinement

  • R[F 2 > 2σ(F 2)] = 0.056
  • wR(F 2) = 0.131
  • S = 1.05
  • 1538 reflections
  • 128 parameters
  • 4 restraints
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.25 e Å−3
  • Δρmin = −0.26 e Å−3

Data collection: SMART (Bruker, 2002 [triangle]); cell refinement: SAINT (Bruker, 2002 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808040221/wn2295sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808040221/wn2295Isup2.hkl

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

Acknowledgments

The author thanks Jiangxi Science and Technology Normal University for supporting this study.

supplementary crystallographic information

Comment

In recent years, N-heterocyclic carboxylic acids have attracted considerable interest as ligands in metal complexes because of their structural diversity (Nie et al., 2007; Sun et al.) and their potential applications as functional materials (Liang et al., 2002; Qin et al., 2002; Li et al., 1998). Sun et al. (2006) have prepared the inner salt, 4-carboxy-2-(pyridinium-4-yl)-1H-imidazole-5-carboxylate monohydrate; in its crystal structure, one carboxyl group is deprotonated and the pyridyl group is protonated. Nie et al. (2007) have reported the mononuclear complex, diaquabis(5-carboxy-2-methyl-1H-imidazole-4-carboxylate- κ2N3,O4)cadmium(II). Imidazole derivatives have a wide range of biological activities such as analgesic (Ucucu et al., 2001), anti-inflammatory (Maeda et al., 1984), antiparasitic (Quattara et al., 1987), antiepileptic and platelet aggregation inhibitors (Seko et al., 1991). I report here the crystal structure of 4-carboxy-2-methyl-1H-3-imidazolium-5-carboxylate monohydrate.

As shown in Fig. 1, the asymmetric unit consists of a neutral C6H6N2O4 molecule and one water molecule. The organic molecule, excluding methyl hydrogen atoms, is essentially planar, with an r.m.s. deviation of 0.0156 (1) Å. The C1-containing carboxylate group forms an intramolecular hydrogen bond with the neighboring C5-containing carboxyl group.

In the crystal structure, intermolecular N—H···O hydrogen bonds link the molecules into chains along the b axis; these chains are further linked via O—H···O hydrogen bonds involving the water O atoms and carboxyl O atoms, generating a two-dimensional supramolecular framework (Fig. 2).

Experimental

The title compound was synthesized according to a revised procedure (Anderson et al., 1989). 2-Methylimidazole (3.0 g) was added to a mixture of concentrated sulfuric acid (40 ml) and water (30 ml) at 363 K. This was followed by the careful addition of powdered potassium dichromate (22 g). After 30 min the mixture was poured into ice-cold water. The white precipitates were collected by filtration, and washed with water. Recrystallization from hot water afforded colorless block crystals of the title compound. Yield: 1.8 g (44%).

Refinement

The carboxyl and water H atoms were located in a difference Fourier map and refined with Uiso(H) = 1.5Ueq(O). The O—H distances of the water molecule were restrained to 0.85 (1) Å; however, that of the carboxyl was refined freely. All other H-atoms were positioned geometrically and refined using a riding model with C—H (methyl) = 0.96 Å, N—H = 0.86 Å; Uiso(H) = kUeq(carrier atom), where k = 1.2 for N and 1.5 for C.

Figures

Fig. 1.
The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level. Hydrogen atoms are drawn as spheres of arbitrary radius.
Fig. 2.
Packing diagram of the title structure, showing the intermolecular N—H···O and O—H···O hydrogen bonds as dashed lines. Methyl H atoms are omitted for clarity.

Crystal data

C6H6N2O4·H2OF(000) = 392
Mr = 188.14Dx = 1.589 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 927 reflections
a = 8.491 (2) Åθ = 2.4–24.3°
b = 14.280 (4) ŵ = 0.14 mm1
c = 6.5385 (17) ÅT = 295 K
β = 97.386 (5)°Block, colorless
V = 786.2 (4) Å30.23 × 0.09 × 0.08 mm
Z = 4

Data collection

Bruker SMART APEX area-detector diffractometer1538 independent reflections
Radiation source: fine-focus sealed tube1246 reflections with I > 2σ(I)
graphiteRint = 0.032
[var phi] and ω scansθmax = 26.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)h = −8→10
Tmin = 0.969, Tmax = 0.995k = −17→17
4506 measured reflectionsl = −8→7

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.131H atoms treated by a mixture of independent and constrained refinement
S = 1.05w = 1/[σ2(Fo2) + (0.0559P)2 + 0.4711P] where P = (Fo2 + 2Fc2)/3
1538 reflections(Δ/σ)max < 0.001
128 parametersΔρmax = 0.25 e Å3
4 restraintsΔρmin = −0.26 e Å3

Special details

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)

xyzUiso*/Ueq
O10.5312 (2)0.88207 (11)0.2430 (3)0.0404 (5)
O30.1439 (2)0.68027 (12)0.1429 (3)0.0430 (5)
H30.191 (3)0.7337 (12)0.157 (5)0.065*
N20.5293 (2)0.56877 (13)0.2531 (3)0.0287 (5)
H20.51260.50940.25010.034*
O20.2822 (2)0.83103 (12)0.1822 (3)0.0436 (5)
N10.6490 (2)0.70121 (13)0.2840 (3)0.0284 (5)
H10.72320.74240.30450.034*
C20.4901 (3)0.72074 (15)0.2375 (3)0.0265 (5)
C30.4139 (3)0.63632 (15)0.2178 (3)0.0265 (5)
C10.4314 (3)0.81906 (15)0.2198 (4)0.0303 (6)
C40.6708 (3)0.60933 (16)0.2927 (4)0.0283 (5)
C50.2437 (3)0.61108 (17)0.1680 (4)0.0335 (6)
O40.2045 (2)0.52952 (12)0.1540 (3)0.0506 (6)
C60.8249 (3)0.56070 (18)0.3429 (4)0.0405 (7)
H6A0.85570.53330.21990.061*
H6B0.81480.51240.44250.061*
H6C0.90430.60490.39870.061*
O1W0.8762 (2)0.83332 (13)0.3359 (4)0.0563 (6)
H1WA0.961 (3)0.827 (2)0.419 (5)0.084*
H1WB0.840 (4)0.8884 (12)0.345 (5)0.084*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0417 (11)0.0175 (8)0.0613 (13)−0.0014 (7)0.0041 (9)−0.0002 (8)
O30.0293 (10)0.0278 (10)0.0697 (14)−0.0004 (7)−0.0020 (9)0.0000 (9)
N20.0313 (11)0.0172 (9)0.0371 (12)0.0002 (8)0.0025 (9)−0.0009 (8)
O20.0360 (11)0.0272 (9)0.0664 (14)0.0062 (8)0.0025 (9)0.0008 (8)
N10.0287 (11)0.0206 (10)0.0351 (11)−0.0044 (8)0.0016 (8)−0.0009 (8)
C20.0288 (12)0.0229 (11)0.0275 (13)0.0001 (9)0.0028 (10)−0.0002 (9)
C30.0330 (13)0.0200 (11)0.0267 (12)0.0015 (9)0.0042 (10)0.0005 (9)
C10.0380 (14)0.0214 (12)0.0315 (14)0.0013 (10)0.0046 (10)0.0005 (9)
C40.0304 (13)0.0230 (12)0.0311 (13)−0.0008 (9)0.0028 (10)−0.0005 (9)
C50.0307 (13)0.0278 (14)0.0413 (15)−0.0016 (10)0.0023 (11)0.0009 (10)
O40.0399 (11)0.0261 (10)0.0835 (16)−0.0082 (8)−0.0013 (10)−0.0008 (9)
C60.0346 (14)0.0309 (13)0.0551 (18)0.0050 (11)0.0019 (12)0.0018 (12)
O1W0.0395 (12)0.0292 (10)0.0942 (18)−0.0035 (8)−0.0148 (11)0.0009 (11)

Geometric parameters (Å, °)

O1—C11.232 (3)C2—C31.367 (3)
O3—C51.299 (3)C2—C11.489 (3)
O3—H30.861 (10)C3—C51.484 (3)
N2—C41.329 (3)C4—C61.481 (3)
N2—C31.373 (3)C5—O41.212 (3)
N2—H20.8600C6—H6A0.9600
O2—C11.271 (3)C6—H6B0.9600
N1—C41.325 (3)C6—H6C0.9600
N1—C21.373 (3)O1W—H1WA0.849 (10)
N1—H10.8600O1W—H1WB0.850 (10)
C5—O3—H3112 (2)O2—C1—C2117.2 (2)
C4—N2—C3109.54 (19)N1—C4—N2107.8 (2)
C4—N2—H2125.2N1—C4—C6126.1 (2)
C3—N2—H2125.2N2—C4—C6126.2 (2)
C4—N1—C2109.81 (19)O4—C5—O3123.6 (2)
C4—N1—H1125.1O4—C5—C3120.0 (2)
C2—N1—H1125.1O3—C5—C3116.4 (2)
C3—C2—N1106.37 (19)C4—C6—H6A109.5
C3—C2—C1132.4 (2)C4—C6—H6B109.5
N1—C2—C1121.2 (2)H6A—C6—H6B109.5
C2—C3—N2106.5 (2)C4—C6—H6C109.5
C2—C3—C5132.1 (2)H6A—C6—H6C109.5
N2—C3—C5121.3 (2)H6B—C6—H6C109.5
O1—C1—O2125.4 (2)H1WA—O1W—H1WB110 (2)
O1—C1—C2117.4 (2)
C4—N1—C2—C30.1 (3)C3—C2—C1—O21.2 (4)
C4—N1—C2—C1179.5 (2)N1—C2—C1—O2−178.0 (2)
N1—C2—C3—N20.0 (2)C2—N1—C4—N2−0.1 (3)
C1—C2—C3—N2−179.3 (2)C2—N1—C4—C6−178.7 (2)
N1—C2—C3—C5−179.6 (2)C3—N2—C4—N10.1 (3)
C1—C2—C3—C51.1 (4)C3—N2—C4—C6178.7 (2)
C4—N2—C3—C2−0.1 (3)C2—C3—C5—O4178.1 (3)
C4—N2—C3—C5179.6 (2)N2—C3—C5—O4−1.4 (4)
C3—C2—C1—O1−178.9 (2)C2—C3—C5—O3−2.3 (4)
N1—C2—C1—O11.9 (3)N2—C3—C5—O3178.2 (2)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O1W—H1WB···O4i0.85 (1)2.05 (1)2.887 (3)168 (4)
O1W—H1WA···O3ii0.85 (1)2.00 (1)2.839 (3)173 (4)
N2—H2···O1iii0.861.862.716 (3)176
N1—H1···O1W0.861.832.689 (3)177
O3—H3···O20.86 (1)1.59 (2)2.447 (2)179 (3)

Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) x+1, −y+3/2, z+1/2; (iii) −x+1, y−1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WN2295).

References

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