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ld2040 scheme

Acta Cryst. (2012). E68, o134-o135    [ doi:10.1107/S1600536811052998 ]

1H-Imidazol-3-ium-4-carboxylate

Q. Cao, B.-R. Duan, B. Zhu and Z. Cao

Abstract top

In the title compound, C4H4N2O2, both imidazole N atoms are protonated and carboxylate group is deprotonated, resulting in a zwitterion. The molecule is essentially planar, with an r.m.s. deviation of 0.012 (1) Å. In the crystal, N-H...O hydrogen bonds and [pi]-[pi] stacking interactions [centroid-centroid distance = 3.674 (2) Å] between the imidazole rings link the molecules into a three-dimensional supramolecular network.

Comment top

The organic ligands containing N and O donors, especially the N-heterocyclic carboxylates, are ideal candidates for constructing novel metal coordination polymers, because of their versatile coordination modes and potential hydrogen bonding donors and acceptors. Particular attention has been paid to the 1H-imidazole-4,5-dicarboxylic acid ligand (H3IDC), because it can coordinate with metal ions in different coordination fashions to offer a series of complexes with diverse structures and interesting properties (Alkordi, Liu et al., 2008; Alkordi, Brant et al., 2009; Gu et al., 2010; Lu et al., 2006; Nouar et al., 2009; Wang et al., 2010). Recently, an analogue of H3IDC, 1H-imidazole-4-carboxylic acid (H2IMC), has also been used to prepare new coordination polymers (Haggag, 2005; Starosta & Leciejewicz, 2006; Gryz et al., 2007; Yin et al., 2009; Shuai et al., 2011; Zheng et al., 2011). However, the crystal structure of H2IMC ligand has not been determined. With this in mind, we attempteted to obtain its crystal structure that is reported here.

As illustrated in Fig. 1, the title compound, C4H4N2O2, crystallizes as a zwitterion in which the imidazole N atom is protonated and the carboxylate group is deprotonateded. In the crystal structure, intermolecular N2—H2···O2i and N1—H1···O1ii hydrogen bonds (Table 1) [symmetry code: (i) -x + 1/2, y - 1/2, z + 1/2; (ii) -x,-y + 1, z + 1/2] between the imidazole N—H groups and carboxylate O atoms link the molecules into a three-dimensional supramolecular network (Fig. 2). Moreover, the crystal structure is further stabilized by π-π stacking interactions between neighbouring imidazole rings [N2—C4—N1—C2—C3 and N2v—C4v—N1v—C2v—C3v, symmetry code: (v) x, y, z + 1], with centroid···centroid distances of 3.674 (2) Å (Fig. 2).

Related literature top

For general background to the construction of coordination polymers based on 1H-imidazole-4,5-dicarboxylic acid, see: Alkordi, Liu et al. (2008); Alkordi, Brant et al. (2009); Gu et al. (2010); Lu et al. (2006); Nouar et al. (2009); Wang et al. (2010). For related complexes with 1H-imidazole-4-carboxylic acid, see: Haggag (2005); Starosta & Leciejewicz (2006); Gryz et al. (2007); Yin et al. (2009); Shuai et al. (2011); Zheng et al. (2011). For the synthesis of 1H-imidazole-4-carboxylic acid, see: Davis et al. (1982).

Experimental top

The compound was synthesized from 1H-imidazole-4,5-dicarboxylic acid according to the method reported in the literature (Davis et al., 1982). Colourless single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in water at room temperature.

Refinement top

All non-hydrogen atoms were assigned anisotropic displacement parameters in the refinement. The zwitter-ionic structure was established from a difference Fourier synthesis. Consequently, all hydrogen atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 Å and N—H =0.86 Å and with Uiso(H) =1.2 Ueq(C, N). Since this is a light atom structure (does not contain any atoms heavier than Si) and since the data collection was carried out using Mo radiation, it was not possible to unambiguously determine the absolute configuration of this molecule. In the absence of significant anomalous scattering effects Friedel pairs have been merged.

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The structure of the title compound, showing the atom-labelling scheme and displacement ellipsoids drawn at the 30% probability level.
[Figure 2] Fig. 2. A view showing part of the three-dimensional supramolecular network linked by N–H···O hydrogen bonds and π-π stacking interactions. Hydrogen bonds and π-π stacking interactions are shown as dashed lines. Symmetry codes: (i) -x + 1/2, y - 1/2, z + 1/2; (ii) -x, -y + 1, z + 1/2; (v) x, y, z + 1.
1H-Imidazol-3-ium-4-carboxylate top
Crystal data top
C4H4N2O2F(000) = 232
Mr = 112.09Dx = 1.657 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 1380 reflections
a = 10.474 (6) Åθ = 2.6–27.0°
b = 11.676 (7) ŵ = 0.14 mm1
c = 3.674 (2) ÅT = 298 K
V = 449.3 (5) Å3Block, colourless
Z = 40.25 × 0.21 × 0.18 mm
Data collection top
Bruker APEXII CCD area-detector
diffractometer
510 independent reflections
Radiation source: fine-focus sealed tube480 reflections with I > 2σ(I)
graphiteRint = 0.023
phi and ω scansθmax = 26.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1212
Tmin = 0.967, Tmax = 0.976k = 1412
2280 measured reflectionsl = 44
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)] = 0.029Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.083H-atom parameters constrained
S = 1.10 w = 1/[σ2(Fo2) + (0.0578P)2 + 0.0406P]
where P = (Fo2 + 2Fc2)/3
510 reflections(Δ/σ)max < 0.001
73 parametersΔρmax = 0.12 e Å3
1 restraintΔρmin = 0.19 e Å3
Crystal data top
C4H4N2O2V = 449.3 (5) Å3
Mr = 112.09Z = 4
Orthorhombic, Pna21Mo Kα radiation
a = 10.474 (6) ŵ = 0.14 mm1
b = 11.676 (7) ÅT = 298 K
c = 3.674 (2) Å0.25 × 0.21 × 0.18 mm
Data collection top
Bruker APEXII CCD area-detector
diffractometer
510 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
480 reflections with I > 2σ(I)
Tmin = 0.967, Tmax = 0.976Rint = 0.023
2280 measured reflectionsθmax = 26.0°
Refinement top
R[F2 > 2σ(F2)] = 0.029H-atom parameters constrained
wR(F2) = 0.083Δρmax = 0.12 e Å3
S = 1.10Δρmin = 0.19 e Å3
510 reflectionsAbsolute structure: ?
73 parametersFlack parameter: ?
1 restraintRogers parameter: ?
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
C20.15183 (19)0.33109 (16)0.6250 (7)0.0265 (5)
C10.20900 (19)0.44287 (17)0.5153 (6)0.0268 (5)
N20.10851 (15)0.15065 (14)0.7501 (6)0.0302 (5)
H20.11490.07740.76600.036*
C40.0113 (2)0.21278 (18)0.8693 (7)0.0301 (5)
H40.06100.18440.98530.036*
O20.31910 (13)0.43682 (12)0.3734 (5)0.0361 (5)
O10.14526 (14)0.53104 (13)0.5736 (6)0.0367 (5)
N10.03417 (16)0.32279 (14)0.7956 (6)0.0284 (5)
H10.01580.37910.84560.034*
C30.1970 (2)0.22218 (17)0.5977 (7)0.0280 (5)
H30.27430.20030.49400.034*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C20.0254 (9)0.0223 (10)0.0320 (13)0.0003 (8)0.0016 (10)0.0003 (10)
C10.0295 (11)0.0190 (9)0.0319 (13)0.0011 (8)0.0047 (9)0.0035 (9)
N20.0323 (9)0.0181 (8)0.0401 (11)0.0007 (7)0.0033 (9)0.0011 (9)
C40.0275 (10)0.0271 (10)0.0358 (14)0.0035 (8)0.0004 (9)0.0032 (11)
O20.0324 (8)0.0235 (7)0.0524 (12)0.0013 (6)0.0078 (8)0.0043 (9)
O10.0352 (8)0.0203 (7)0.0545 (12)0.0047 (6)0.0018 (8)0.0025 (9)
N10.0279 (9)0.0203 (8)0.0371 (11)0.0024 (7)0.0016 (9)0.0004 (8)
C30.0261 (9)0.0222 (10)0.0357 (14)0.0005 (8)0.0022 (10)0.0017 (10)
Geometric parameters (Å, °) top
C2—C31.361 (3)N2—C31.368 (3)
C2—N11.386 (3)N2—H20.8600
C2—C11.491 (3)C4—N11.334 (3)
C1—O11.246 (3)C4—H40.9300
C1—O21.267 (3)N1—H10.8600
N2—C41.324 (3)C3—H30.9300
C3—C2—N1106.10 (17)N2—C4—N1108.81 (19)
C3—C2—C1131.2 (2)N2—C4—H4125.6
N1—C2—C1122.71 (17)N1—C4—H4125.6
O1—C1—O2127.19 (19)C4—N1—C2108.57 (17)
O1—C1—C2117.49 (18)C4—N1—H1125.7
O2—C1—C2115.32 (18)C2—N1—H1125.7
C4—N2—C3108.78 (17)C2—C3—N2107.74 (19)
C4—N2—H2125.6C2—C3—H3126.1
C3—N2—H2125.6N2—C3—H3126.1
C3—C2—C1—O1180.0 (3)C3—C2—N1—C40.5 (3)
N1—C2—C1—O11.9 (3)C1—C2—N1—C4178.0 (2)
C3—C2—C1—O20.5 (4)N1—C2—C3—N20.2 (3)
N1—C2—C1—O2177.6 (2)C1—C2—C3—N2178.1 (2)
C3—N2—C4—N10.4 (3)C4—N2—C3—C20.1 (3)
N2—C4—N1—C20.6 (3)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N2—H2···O2i0.861.822.648 (2)160.
N1—H1···O1ii0.861.912.736 (2)161.
Symmetry codes: (i) −x+1/2, y−1/2, z+1/2; (ii) −x, −y+1, z+1/2.
Table 1
Hydrogen-bond geometry (Å, °)
top
D—H···AD—HH···AD···AD—H···A
N2—H2···O2i0.861.822.648 (2)160.
N1—H1···O1ii0.861.912.736 (2)161.
Symmetry codes: (i) −x+1/2, y−1/2, z+1/2; (ii) −x, −y+1, z+1/2.
Acknowledgements top

The authors gratefully acknowledge the Scientific Research Foundation of Weinan Normal University (grant No. 07YKZ027), the Natural Science Foundation of Yantai University (grant No. HY10Z10), the Science and Technology Research Projects of Yantai City (grant No. 2006GGAO00143), the Science and Technology Research Projects of Shandong Province (grant No. 2008 GG10003020) and the National Science and Technology Research Projects (grant No. 2004BA320B) for supporting this work.

references
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