research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Crystal structure of 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate

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aLaboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal, and bICMUB UMR 6302, Université de Bourgogne, Faculté des Sciences, 9 avenue Alain Savary, 21000 Dijon, France
*Correspondence e-mail: mouhamadoubdiop@gmail.com, hcattey@u-bourgogne.fr

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 1 July 2016; accepted 7 July 2016; online 12 July 2016)

Single crystals of the title mol­ecular salt, C4H7N2+·HC2O4·2H2O, were isolated from the reaction of 2-methyl-1H-imidazole and oxalic acid in a 1:1 molar ratio in water. In the crystal, the cations and anions are positioned alternately along an infinite [010] ribbon and linked together through bifurcated N—H⋯(O,O) hydrogen bonds. The water mol­ecules of crystallization link the chains into (10-1) bilayers, with the methyl groups of the cations organized in an isotactic manner.

1. Chemical context

Imidazolium-type building blocks are useful in the field of crystal engineering (MacDonald et al., 2001[MacDonald, J. C., Dorrestein, P. C. & Pilley, M. M. (2001). Cryst. Growth Des. 1, 29-38.]). With many possibilities of substitution (involving various positions around the five-membered ring) and via the propagation of multidirectional hydrogen-bonding inter­actions, they easily lead to the self-assembly of poly-dimensional packing net­works. In 2010, Callear and co-workers described various topologies based on imidazolium/di­carb­oxy­lic acid combinations and showed the crystal-packing effects of substitution in the imidazole ring (Callear et al., 2010[Callear, S. K., Hursthouse, M. B. & Threlfall, T. L. (2010). CrystEngComm, 12, 898-908.]). In this context, and for some time, our group has focused on the contribution of the 2-methyl­imidazolium cation as a co-crystal in organic (Diop, Diop & Maris, 2016[Diop, M. B., Diop, L. & Maris, T. (2016). Acta Cryst. E72, 482-485.]) and organic–inorganic hybrid salts (Diop, Diop & Maris, 2015[Diop, M. B., Diop, L. & Maris, T. (2015). Acta Cryst. E71, 1064-1066.]; Diop, Diop, Plasseraud & Maris, 2015[Diop, M. B., Diop, L., Plasseraud, L. & Maris, T. (2015). Acta Cryst. E71, 520-522.], 2016[Diop, M. B., Diop, L., Plasseraud, L. & Maris, T. (2016). Acta Cryst. E72, 355-357.]). Continuing our ongoing studies in this field, we report herein the crystal structure of a new hydrated organic salt, namely 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate, (I)[link], isolated by reacting 2-methyl-1H-imidazole and oxalic acid in a 1:1 molar ratio in water.

[Scheme 1]

2. Structural comments

The asymmetric unit of the title molecular salt (I)[link] consists of four components, i.e. one 2-methyl-1H-imidazol-3-ium cation, one hydrogen oxalate anion and two solvent water mol­ecules (Fig. 1[link]). The hydrogen oxalate anion is slightly twisted, with O1—C6—C5—O3 and O2—C6—C5—O4 torsion angles of 6.9 (3) and 7.3 (3)°, respectively. The C5—O3 and C5—O4 bonds are almost equal in length [1.249 (2) and 1.245 (2) Å, respectively], whereas C6—O2 is typical for a >C=O group [1.206 (2) Å] and C6—O1 has a normal C—OH bond length [1.306 (2) Å] (Adams, 1978[Adams, J. M. (1978). Acta Cryst. B34, 1218-1220.]).

[Figure 1]
Figure 1
The mol­ecular structure of (I)[link], showing the atom labelling. Displacement ellipsoids are draw at the 50% probability level.

3. Supra­molecular features

Hydrogen-bonding inter­actions are listed in Table 1[link] and illustrated in Fig. 2[link]. Both N—H groups of the imidazolium cation are involved in asymmetric bifurcated N—H⋯(O,O) hydrogen bonds with two distinct neighbouring hydrogen oxalate anions, which initiates the propagation of an infinite ribbon along the b-axis direction. Considering the orientation of the methyl groups of the cations along the ribbon, the sequence can be described as `isotactic'. The cations and anions are positioned alternately and are almost coplanar [dihedral angle between adjacent species = 1.15 (9)°].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1⋯O3 0.88 1.94 2.811 (2) 172
N1—H1⋯O1 0.88 2.50 2.991 (2) 116
N2—H2⋯O4i 0.88 1.97 2.842 (2) 169
N2—H2⋯O2i 0.88 2.49 2.977 (2) 116
O1—H1A⋯O5 0.84 1.69 2.5234 (19) 169
O6—H6A⋯O2ii 0.85 2.02 2.7893 (19) 150
O6—H6B⋯O3iii 0.85 1.87 2.700 (2) 166
O5—H5A⋯O6 0.85 1.82 2.672 (2) 176
O5—H5B⋯O4iv 0.85 1.88 2.720 (2) 167
Symmetry codes: (i) x, y-1, z; (ii) [-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]; (iii) -x+1, -y+1, -z+1; (iv) [x-{\script{1\over 2}}, -y+{\script{3\over 2}}, z-{\script{1\over 2}}].
[Figure 2]
Figure 2
The crystal packing of the title salt, showing a two-dimensional bilayer-like arrangement through N—H⋯(O,O) and O—H⋯O inter­actions. H atoms not involved in hydrogen bonding have been omitted for clarity. Colour code: C dark grey, H light grey, O red and N blue.

As well as the cation-to-anion links, the OH group of the anion acts as a hydrogen-bond donor with one mol­ecule of water, which is also the donor for hydrogen-bond inter­actions with (i) a second mol­ecule of water and (ii) an O atom of a hydrogen oxalate anion involved in a neighbouring ribbon. The second water mol­ecule also bridges two distinct hydrogen oxalate anions through two O—H⋯O hydrogen bonds. Thus, all the O atoms of the hydrogen oxalate anions are involved in the hydrogen-bonding network.

The supra­molecular arrangement depicted in Fig. 2[link] relies on the contributions of the four components of (I)[link] and can be described as resulting from three levels of organization: (i) C4H7N2+ and HC2O4 assembled in infinite ribbons; (ii) parallel ribbons of C4H7N2+/HC2O4 connected together by water mol­ecules, which leads to a staircase–sheet structure; (iii) sheets stacked in pairs which can be described as a two-dimensional bilayer-like arrangement propagating in (10[\overline{1}]). This final organization is again induced by the formation of hydrogen-bonding inter­actions between the water mol­ecules contained in each sheet. The inter-sheet distance is about 3.4 Å. Inter­estingly, all the methyl substituents of the imidazolium rings are oriented in the same direction along the c axis. Thus, the isotacticity observed at the ribbon level is also extended across the supra­molecular network.

4. Database survey

To date, 176 structures of hydrogen oxalates have been deposited in the Cambridge Structural Database (CSD; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]). Among these, five hits describe imidazolium salts or derivatives, i.e. imidazolium hydrogen oxalate [CSD refcodes MEQPAZ (MacDonald et al., 2001[MacDonald, J. C., Dorrestein, P. C. & Pilley, M. M. (2001). Cryst. Growth Des. 1, 29-38.]) and MEQPAZ01 (Prasad et al., 2002[Prasad, R. A., Neeraj, S., Vaidhyanathan, R. & Natarajan, S. (2002). J. Solid State Chem. 166, 128-141.])], (S)-(+)-2-[2-(biphenyl-2-yl)-1-methyl­eth­yl]-4,5-di­hydro-1H-imidazolium hydrogen ox­alate (GAQTOI; Giannella et al., 2005[Giannella, M., Gentili, F., Bruni, B., Messori, L. & Di Vaira, M. (2005). Acta Cryst. E61, o2376-o2378.]), 1,3-diisopropyl-4,5-di­methyl­imidazolium hydrogen oxalate (DOHTOK; Abu-Rayyan et al., 2008[Abu-Rayyan, A., Abu-Salem, Q., Kuhn, N., Maichle-Mossmer, C., Mallah, E. & Steimann, M. (2008). Z. Naturforsch. Teil B, 63, 1015-1019.]), (S)-(−)-6-(4-bromo­phen­yl)-2,3,5,6-tetra­hydro­thia­zolo[2,3-b]imidazolium hydrogen oxalate (ROF­QAF; Minor & Chruszcz, 2008[Minor, T. & Chruszcz, M. (2008). Acta Cryst. E64, o1954.]).

5. Synthesis and crystallization

Equimolar solutions of 2-methyl-1H-imidazole (6.51 g, 79.39 mmol) and H2C2O4·2H2O (10.00 g, 79.39 mmol) in water (100 ml) were mixed together at room temperature (301 K). Needle-shaped colourless crystals of (I)[link] were obtained after one week by evaporation of the solvent at 333 K (yield 10.83 g, 65.5%).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All H atoms on C, O and N atoms were placed at calculated positions using a riding model, with aromatic C—H = 0.95 Å and aromatic N—H = 0.88 Å, and with Uiso(H) = 1.2Ueq(C,N), or hy­droxy O—H = 0.84 Å, water O—H = 0.85 Å and methyl C—H = 0.98 Å, and with Uiso(H) = 1.5Ueq(O,C).

Table 2
Experimental details

Crystal data
Chemical formula C4H7N2+·C2HO4·2H2O
Mr 208.18
Crystal system, space group Monoclinic, P21/n
Temperature (K) 115
a, b, c (Å) 6.7139 (7), 9.5116 (7), 15.2115 (13)
β (°) 101.151 (6)
V3) 953.07 (15)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.13
Crystal size (mm) 0.30 × 0.10 × 0.08
 
Data collection
Diffractometer Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2014[Bruker (2014). APEX2 and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.691, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 15445, 2187, 1258
Rint 0.063
(sin θ/λ)max−1) 0.650
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.115, 1.01
No. of reflections 2187
No. of parameters 135
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.40, −0.23
Computer programs: APEX2 and SAINT (Bruker, 2013[Bruker (2013). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXS2013 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Supporting information


Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

2-Methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate top
Crystal data top
C4H7N2+·C2HO4·2H2OF(000) = 440
Mr = 208.18Dx = 1.451 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 6.7139 (7) ÅCell parameters from 2578 reflections
b = 9.5116 (7) Åθ = 3.5–26.4°
c = 15.2115 (13) ŵ = 0.13 mm1
β = 101.151 (6)°T = 115 K
V = 953.07 (15) Å3Needle, colourless
Z = 40.30 × 0.10 × 0.08 mm
Data collection top
Bruker APEXII CCD
diffractometer
2187 independent reflections
Radiation source: X-ray tube, Siemens KFF Mo 2K-90C1258 reflections with I > 2σ(I)
TRIUMPH curved crystal monochromatorRint = 0.063
Detector resolution: 1024 x 1024 pixels mm-1θmax = 27.5°, θmin = 2.5°
φ and ω scans'h = 88
Absorption correction: multi-scan
SADABS (Bruker, 2014) was used for absorption correction. wR2(int) was 0.0622 before and 0.0548 after correction. The Ratio of minimum to maximum transmission is 0.9269. The λ/2 correction factor is 0.00150.
k = 1212
Tmin = 0.691, Tmax = 0.746l = 1919
15445 measured reflections
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.115 w = 1/[σ2(Fo2) + (0.0448P)2 + 0.3824P]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
2187 reflectionsΔρmax = 0.40 e Å3
135 parametersΔρmin = 0.23 e Å3
Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O40.3344 (2)0.84241 (13)0.62704 (8)0.0224 (3)
O30.3377 (2)0.60714 (13)0.62300 (9)0.0247 (3)
O10.1928 (2)0.60978 (13)0.44891 (9)0.0254 (4)
H1A0.15720.61960.39320.038*
O60.3979 (2)0.45757 (14)0.22494 (10)0.0314 (4)
H6A0.37240.39540.18420.047*
H6B0.48830.42700.26770.047*
O20.2253 (2)0.84212 (14)0.44546 (9)0.0311 (4)
O50.1121 (3)0.61142 (17)0.27986 (9)0.0357 (4)
H5A0.19860.56150.25990.054*
H5B0.01830.63600.23670.054*
N20.2719 (2)0.11229 (16)0.54620 (11)0.0231 (4)
H20.28240.02440.56470.028*
N10.2803 (2)0.33729 (17)0.54697 (11)0.0245 (4)
H10.29700.42480.56570.029*
C50.3089 (3)0.7264 (2)0.58854 (12)0.0186 (4)
C60.2361 (3)0.7327 (2)0.48607 (12)0.0187 (4)
C10.3139 (3)0.2239 (2)0.59833 (14)0.0244 (5)
C20.2138 (3)0.2951 (2)0.45809 (14)0.0287 (5)
H2A0.17890.35490.40740.034*
C40.3880 (3)0.2233 (2)0.69571 (13)0.0291 (5)
H4A0.33000.14280.72220.044*
H4B0.34720.31060.72150.044*
H4C0.53640.21600.70850.044*
C30.2088 (3)0.1547 (2)0.45810 (14)0.0296 (5)
H30.16960.09540.40750.036*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O40.0311 (8)0.0146 (7)0.0198 (7)0.0010 (6)0.0005 (6)0.0023 (6)
O30.0375 (9)0.0141 (7)0.0196 (7)0.0018 (6)0.0018 (6)0.0018 (6)
O10.0417 (10)0.0159 (7)0.0160 (7)0.0014 (6)0.0010 (7)0.0013 (5)
O60.0439 (11)0.0223 (8)0.0224 (8)0.0083 (7)0.0075 (7)0.0045 (6)
O20.0568 (11)0.0135 (7)0.0203 (8)0.0004 (7)0.0009 (7)0.0024 (6)
O50.0412 (11)0.0421 (10)0.0201 (8)0.0125 (8)0.0030 (7)0.0046 (7)
N20.0282 (10)0.0116 (8)0.0285 (10)0.0004 (7)0.0026 (8)0.0012 (7)
N10.0280 (10)0.0128 (8)0.0322 (10)0.0004 (7)0.0043 (8)0.0006 (7)
C50.0192 (11)0.0153 (9)0.0200 (10)0.0020 (8)0.0010 (8)0.0006 (8)
C60.0198 (10)0.0145 (9)0.0209 (10)0.0008 (8)0.0016 (8)0.0011 (8)
C10.0218 (11)0.0178 (9)0.0332 (12)0.0000 (9)0.0047 (9)0.0005 (9)
C20.0363 (13)0.0221 (11)0.0265 (11)0.0009 (10)0.0029 (10)0.0007 (9)
C40.0348 (13)0.0238 (10)0.0282 (11)0.0002 (10)0.0053 (10)0.0016 (9)
C30.0395 (14)0.0205 (11)0.0276 (12)0.0001 (10)0.0033 (10)0.0028 (9)
Geometric parameters (Å, º) top
O4—C51.245 (2)N1—H10.8800
O3—C51.249 (2)N1—C11.325 (3)
O1—H1A0.8400N1—C21.398 (2)
O1—C61.306 (2)C5—C61.542 (3)
O6—H6A0.8499C1—C41.469 (3)
O6—H6B0.8501C2—H2A0.9500
O2—C61.206 (2)C2—C31.336 (3)
O5—H5A0.8500C4—H4A0.9800
O5—H5B0.8500C4—H4B0.9800
N2—H20.8800C4—H4C0.9800
N2—C11.323 (2)C3—H30.9500
N2—C31.385 (2)
C6—O1—H1A109.5N2—C1—N1107.91 (17)
H6A—O6—H6B109.5N2—C1—C4126.36 (18)
H5A—O5—H5B109.5N1—C1—C4125.72 (18)
C1—N2—H2125.2N1—C2—H2A126.6
C1—N2—C3109.64 (16)C3—C2—N1106.85 (18)
C3—N2—H2125.2C3—C2—H2A126.6
C1—N1—H1125.6C1—C4—H4A109.5
C1—N1—C2108.83 (16)C1—C4—H4B109.5
C2—N1—H1125.6C1—C4—H4C109.5
O4—C5—O3127.68 (17)H4A—C4—H4B109.5
O4—C5—C6115.41 (16)H4A—C4—H4C109.5
O3—C5—C6116.90 (17)H4B—C4—H4C109.5
O1—C6—C5113.79 (16)N2—C3—H3126.6
O2—C6—O1124.38 (17)C2—C3—N2106.76 (18)
O2—C6—C5121.81 (18)C2—C3—H3126.6
O4—C5—C6—O1173.95 (17)C1—N1—C2—C30.0 (2)
O4—C5—C6—O27.3 (3)C2—N1—C1—N20.0 (2)
O3—C5—C6—O16.9 (3)C2—N1—C1—C4179.0 (2)
O3—C5—C6—O2171.78 (19)C3—N2—C1—N10.0 (2)
N1—C2—C3—N20.0 (2)C3—N2—C1—C4179.1 (2)
C1—N2—C3—C20.0 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O30.881.942.811 (2)172
N1—H1···O10.882.502.991 (2)116
N2—H2···O4i0.881.972.842 (2)169
N2—H2···O2i0.882.492.977 (2)116
O1—H1A···O50.841.692.5234 (19)169
O6—H6A···O2ii0.852.022.7893 (19)150
O6—H6B···O3iii0.851.872.700 (2)166
O5—H5A···O60.851.822.672 (2)176
O5—H5B···O4iv0.851.882.720 (2)167
Symmetry codes: (i) x, y1, z; (ii) x+1/2, y1/2, z+1/2; (iii) x+1, y+1, z+1; (iv) x1/2, y+3/2, z1/2.
 

Acknowledgements

The authors gratefully acknowledge the Cheikh Anta Diop University of Dakar (Senegal), the Centre National de la Recherche Scientifique (CNRS, France) and the University of Burgundy (Dijon, France).

References

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