Bis(2-methyl­imidazolium) terephthalate bis­(2-methyl­imidazole) tetra­hydrate

The title compound, 2C₄H₇N₂⁺·C₈H₄O₄²⁻·2C₄H₆N₂·4H₂O, was formed by the reaction of terephthalic acid (H₂tere) and 2-methyl­imidazole (2-MeIm). The asymmetric unit consists of half a tere dianion, a 2-methyl­imidazolium cation, a neutral 2-MeIm mol­ecule and two solvent water mol­ecules, the formula unit being generated by crystallographic inversion symmetry. A combination of N—H...N, N—H...O, O—H...O and C—H...O hydrogen bonds, C—H...π inter­actions, and π–π inter­actions [with centroid–centroid distances of 3.654 (1) and 3.337 (1) Å] link the independent components into a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.046
• wR factor = 0.151
• Data-to-parameter ratio = 15.5

checkCIF/PLATON results

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Alert level C
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        100 Deg.
PLAT180_ALERT_3_C Check Cell Rounding: # of Values Ending with 0 =          3
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          2
              C4 H7 N2
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          3
              C4 H6 N2

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S1. Comment

As part of our continuing studies involving H-bonding, C–H···π and π–π interactions in organic adducts (Yang and Qu, 2006a,2006b), we report here the molecular and supramolecular structure of an organic analog formed by terephthalic acid acid (tere) and 2-Methylimidazole (2-MeIm), namely Bis(2-Methylimidazolium) terephthalate bis(2-Methylimidazole) tetrahydrate.

In the title compound, the formula unit is composed of a tere dianion which lies on a crystallographic centre of inversion, two 2-MeIm cations, two neutral 2-MeIm molecules and four water solvent molecules (Fig.1). As expected, in the molecular structure both the carboxyl H atoms are transferred to the adjacent imine N atoms. The four incorporated water solvent molecules may help stabilize the crystal structure. However, the reason of the incorporation of another two neutral 2-MeIm molecules whether incidental or inevitable might be confirmed by modulating the reactant molar ration of tere versus 2-MeIm. The further research work is being undertaken.

The supramolecular structure is formed by a combination of N–H···N, N–H···O, O–H···O, C–H···O hydrogen bonds, C–H···π and π–π interactions which can be analysed in terms of several simple substructures.

Firstly, a combination of H-bonding formed between the tere dianions and two water molecules links the three independent components into a two-dimensional network running parallel to the (010) direction which is built from alternating R⁶₄(16) and R⁴₄(12) H-bonding rings (Fig.2) (Bernstein et al., 1995). Secondly, the combination of N2–H2A···O2, N1–H1A···N3, N4–H4C···O4ⁱⁱⁱ and C12–H12B···O3^iv hydrogen bonds [symmetry codes as in Table 1] running along the [01–2] direction (Table 1) links the adjacent networks into a three-dimensional network. Finally, the crystal structure is consolidated by C–H···π [H···Cg = 2.89 Å, C–H···Cg (x,y,-1 + z and -z,-y,-z) = 147°, where Cg is the centroid of the benzene ring] and π–π interactions [Cg1–Cg1 (-1 - x,1 - y,-1 - z) centroid-centroid distance of 3.64 (1) and perpendicular distance of 3.34 Å; where Cg1 is the centroid of ring atoms N3/C9/N4/C/11/C10].

Related literature

For related literature, see: Yang & Qu (2006a,b); Bernstein et al. (1995).

S2. Experimental

All reagents and solvents were used as obtained without further purification. 2:1 molar amount of 2-methylimidazole (0.4 mmol, 32 mg) and terephthalic acid (0.2 mmol, 33 mg) were dissolved in 95% methanol (10 ml). The mixture was stirred for ten minutes at ambient temperature. The resulting colorless solution was kept in air for several days. Crystals suitable for single-crystal X-ray diffraction analysis were grown by slow evaporation of the solution at the bottom of the vessel.

S3. Refinement

H atoms bonded to carbon atoms were located at the geometrical positions with C—H = 0.93 Å (aromatic) and 0.96 Å(methyl), and U_iso(H) = 1.2U_eq(aromatic C) and 1.5U_eq(methyl C). H atoms bonded to N and water O atoms were located from the difference maps with the N(or O)–H distances refined freely and their U_iso values being set 1.2 and 1.5 times of their carrier atoms for N and O atoms, respectively.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON (Spek, 2003).

Figures

	Fig. 1. Molecular structure showing the atom-numbering scheme·Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are shown as dashed lines. Atoms marked with 'a' are realted by the symmetry operator (-x, -y, 1 - z).
	Fig. 2. Part of the crystal structure, showing the formation of the two-dimensional (010) network by hydrogen bonds formed between tere dianions and water molecules. Hydrogen bonds are shown as dashed lines. Atom marked with sign '#' and '$' are at symmetry positions (1 + x,y,z) and (1 - x,-y,-z), respectively.
	Fig. 3. Part of the crystal structure, showing the formation of the three-dimensional netwok by N2–H2A···O2, N1–H1A···N3, N4–H4C···O4^iii and C12–H12B···O3^iv hydrogen bonds. Hydrogen bonds are shown as dashed lines. Symmetry codes as in Table 1.

Bis(2-methylimidazolium) terephthalate bis(2-methylimidazole) tetrahydrate

Crystal data

2C4H7N2^+·C8H4O4^2^−·2C4H6N2·4H2O	Z = 1
Mr = 566.62	F(000) = 302
Triclinic, P1	Dx = 1.268 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.8753 (4) Å	Cell parameters from 3333 reflections
b = 10.5598 (7) Å	θ = 2.4–27.2°
c = 11.2757 (7) Å	µ = 0.10 mm^−1
α = 71.105 (1)°	T = 297 K
β = 78.984 (1)°	Block, colorless
γ = 74.738 (1)°	0.40 × 0.23 × 0.20 mm
V = 742.17 (8) Å^3

Data collection

Bruker SMART APEX CCD area-detector diffractometer	3175 independent reflections
Radiation source: fine focus sealed Siemens Mo tube	2301 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.051
0.3° wide ω exposures scans	θmax = 27.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −8→8
Tmin = 0.956, Tmax = 0.981	k = −13→13
8374 measured reflections	l = −14→14

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.046	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.151	w = 1/[σ^2(Fo^2) + (0.0879P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max = 0.002
3175 reflections	Δρmax = 0.22 e Å^−3
205 parameters	Δρmin = −0.20 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.091 (12)

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 (Ų)

	x	y	z	Uiso*/Ueq
C1	0.0079 (2)	0.06134 (12)	0.36920 (12)	0.0394 (3)
C2	0.1787 (2)	0.03001 (14)	0.43034 (13)	0.0464 (4)
H2	0.2997	0.0501	0.3841	0.056*
C3	0.1712 (2)	−0.03109 (14)	0.55977 (13)	0.0467 (4)
H3	0.2874	−0.0520	0.5992	0.056*
C4	0.0135 (2)	0.13144 (13)	0.22876 (12)	0.0444 (4)
O1	0.17895 (18)	0.15475 (12)	0.16824 (9)	0.0610 (3)
O2	−0.15041 (18)	0.16592 (12)	0.18190 (10)	0.0645 (4)
O3	0.5850 (2)	0.00820 (15)	0.17111 (15)	0.0791 (4)
H3A	0.662 (4)	0.061 (3)	0.175 (3)	0.119*
H3B	0.484 (4)	0.055 (3)	0.169 (3)	0.119*
C5	−0.2141 (2)	0.33062 (15)	−0.14696 (13)	0.0494 (4)
C6	−0.2641 (3)	0.55302 (18)	−0.18719 (17)	0.0655 (5)
H6	−0.2866	0.6460	−0.2304	0.079*
C7	−0.2412 (3)	0.49718 (18)	−0.06486 (16)	0.0659 (5)
H7	−0.2456	0.5439	−0.0069	0.079*
C8	−0.1840 (3)	0.19192 (17)	−0.16068 (17)	0.0678 (5)
H8A	−0.0457	0.1625	−0.1934	0.102*
H8B	−0.2729	0.1941	−0.2177	0.102*
H8C	−0.2139	0.1291	−0.0798	0.102*
N1	−0.2483 (2)	0.44791 (13)	−0.23739 (12)	0.0556 (4)
H1A	−0.256 (3)	0.4523 (18)	−0.3158 (10)	0.067*
N2	−0.2101 (2)	0.35862 (15)	−0.04107 (12)	0.0565 (4)
H2A	−0.190 (3)	0.290 (2)	0.0328 (19)	0.068*
N3	−0.2465 (2)	0.47035 (12)	−0.48371 (11)	0.0518 (4)
N4	−0.2631 (2)	0.56086 (15)	−0.68589 (12)	0.0561 (4)
H4C	−0.277 (3)	0.6260 (19)	−0.7539 (19)	0.067*
C9	−0.2679 (2)	0.58589 (15)	−0.57583 (14)	0.0489 (4)
C10	−0.2261 (3)	0.36807 (16)	−0.53889 (16)	0.0590 (4)
H10	−0.2077	0.2750	−0.4964	0.071*
C11	−0.2366 (3)	0.42301 (17)	−0.66313 (16)	0.0627 (5)
H11	−0.2277	0.3764	−0.7219	0.075*
C12	−0.2916 (3)	0.72429 (17)	−0.56221 (17)	0.0671 (5)
H12A	−0.3974	0.7377	−0.4954	0.101*
H12B	−0.3263	0.7924	−0.6398	0.101*
H12C	−0.1664	0.7324	−0.5425	0.101*
O4	0.2874 (2)	0.22477 (14)	−0.09066 (13)	0.0788 (4)
H4A	0.318 (4)	0.149 (3)	−0.102 (2)	0.118*
H4B	0.246 (4)	0.207 (3)	−0.007 (3)	0.118*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0524 (8)	0.0337 (6)	0.0306 (7)	−0.0078 (5)	−0.0061 (6)	−0.0079 (5)
C2	0.0505 (8)	0.0529 (8)	0.0344 (7)	−0.0156 (6)	−0.0022 (6)	−0.0088 (6)
C3	0.0518 (9)	0.0516 (8)	0.0351 (7)	−0.0111 (6)	−0.0116 (6)	−0.0066 (6)
C4	0.0591 (9)	0.0395 (7)	0.0329 (7)	−0.0088 (6)	−0.0060 (7)	−0.0092 (6)
O1	0.0697 (8)	0.0692 (7)	0.0340 (6)	−0.0158 (6)	−0.0017 (5)	−0.0032 (5)
O2	0.0730 (8)	0.0773 (8)	0.0369 (6)	−0.0174 (6)	−0.0187 (5)	0.0000 (5)
O3	0.0703 (9)	0.0749 (9)	0.0892 (10)	−0.0070 (7)	−0.0135 (8)	−0.0244 (8)
C5	0.0502 (8)	0.0547 (9)	0.0383 (8)	−0.0104 (6)	−0.0063 (6)	−0.0069 (7)
C6	0.0890 (13)	0.0511 (9)	0.0538 (10)	−0.0136 (8)	−0.0155 (9)	−0.0086 (7)
C7	0.0809 (12)	0.0653 (11)	0.0543 (10)	−0.0108 (9)	−0.0133 (9)	−0.0218 (8)
C8	0.0811 (12)	0.0575 (10)	0.0608 (11)	−0.0162 (8)	−0.0069 (9)	−0.0118 (8)
N1	0.0727 (9)	0.0548 (8)	0.0370 (7)	−0.0150 (6)	−0.0130 (6)	−0.0055 (6)
N2	0.0633 (8)	0.0624 (8)	0.0367 (7)	−0.0072 (6)	−0.0109 (6)	−0.0067 (6)
N3	0.0634 (8)	0.0480 (7)	0.0406 (7)	−0.0113 (6)	−0.0102 (6)	−0.0065 (5)
N4	0.0655 (9)	0.0598 (8)	0.0358 (7)	−0.0082 (6)	−0.0057 (6)	−0.0086 (6)
C9	0.0510 (8)	0.0514 (8)	0.0411 (8)	−0.0114 (6)	−0.0064 (6)	−0.0083 (7)
C10	0.0722 (11)	0.0473 (9)	0.0551 (10)	−0.0091 (7)	−0.0091 (8)	−0.0136 (7)
C11	0.0756 (11)	0.0620 (10)	0.0517 (9)	−0.0064 (8)	−0.0069 (8)	−0.0250 (8)
C12	0.0872 (12)	0.0518 (9)	0.0613 (11)	−0.0180 (8)	−0.0138 (9)	−0.0096 (8)
O4	0.1040 (11)	0.0723 (9)	0.0391 (7)	−0.0065 (7)	−0.0004 (7)	−0.0025 (6)

Geometric parameters (Å, º)

C1—C3^i	1.387 (2)	C8—H8A	0.9600
C1—C2	1.3856 (19)	C8—H8B	0.9600
C1—C4	1.5132 (18)	C8—H8C	0.9600
C2—C3	1.388 (2)	N1—H1A	0.882 (9)
C2—H2	0.9300	N2—H2A	0.92 (2)
C3—C1^i	1.387 (2)	N3—C9	1.3161 (19)
C3—H3	0.9300	N3—C10	1.377 (2)
C4—O1	1.2497 (18)	N4—C9	1.3428 (19)
C4—O2	1.2526 (17)	N4—C11	1.362 (2)
O3—H3A	0.87 (3)	N4—H4C	0.85 (2)
O3—H3B	0.74 (3)	C9—C12	1.482 (2)
C5—N1	1.323 (2)	C10—C11	1.340 (2)
C5—N2	1.3264 (19)	C10—H10	0.9300
C5—C8	1.479 (2)	C11—H11	0.9300
C6—C7	1.335 (2)	C12—H12A	0.9600
C6—N1	1.373 (2)	C12—H12B	0.9600
C6—H6	0.9300	C12—H12C	0.9600
C7—N2	1.364 (2)	O4—H4A	0.81 (3)
C7—H7	0.9300	O4—H4B	0.90 (3)
C3^i—C1—C2	118.56 (12)	H8B—C8—H8C	109.5
C3^i—C1—C4	120.37 (12)	C5—N1—C6	108.47 (13)
C2—C1—C4	121.04 (13)	C5—N1—H1A	122.8 (12)
C1—C2—C3	120.78 (14)	C6—N1—H1A	128.7 (12)
C1—C2—H2	119.6	C5—N2—C7	109.04 (14)
C3—C2—H2	119.6	C5—N2—H2A	120.9 (12)
C1^i—C3—C2	120.65 (13)	C7—N2—H2A	130.1 (12)
C1^i—C3—H3	119.7	C9—N3—C10	105.95 (13)
C2—C3—H3	119.7	C9—N4—C11	108.11 (13)
O1—C4—O2	124.48 (13)	C9—N4—H4C	120.9 (13)
O1—C4—C1	118.14 (12)	C11—N4—H4C	131.0 (13)
O2—C4—C1	117.34 (13)	N3—C9—N4	110.18 (13)
H3A—O3—H3B	102 (3)	N3—C9—C12	125.60 (14)
N1—C5—N2	108.09 (14)	N4—C9—C12	124.22 (14)
N1—C5—C8	126.33 (14)	C11—C10—N3	109.68 (14)
N2—C5—C8	125.58 (14)	C11—C10—H10	125.2
C7—C6—N1	107.40 (15)	N3—C10—H10	125.2
C7—C6—H6	126.3	C10—C11—N4	106.08 (14)
N1—C6—H6	126.3	C10—C11—H11	127.0
C6—C7—N2	106.99 (15)	N4—C11—H11	127.0
C6—C7—H7	126.5	C9—C12—H12A	109.5
N2—C7—H7	126.5	C9—C12—H12B	109.5
C5—C8—H8A	109.5	H12A—C12—H12B	109.5
C5—C8—H8B	109.5	C9—C12—H12C	109.5
H8A—C8—H8B	109.5	H12A—C12—H12C	109.5
C5—C8—H8C	109.5	H12B—C12—H12C	109.5
H8A—C8—H8C	109.5	H4A—O4—H4B	104 (2)
C3^i—C1—C2—C3	0.4 (2)	N1—C5—N2—C7	−0.39 (19)
C4—C1—C2—C3	178.32 (12)	C8—C5—N2—C7	179.21 (16)
C1—C2—C3—C1^i	−0.4 (2)	C6—C7—N2—C5	−0.1 (2)
C3^i—C1—C4—O1	−178.91 (12)	C10—N3—C9—N4	0.36 (17)
C2—C1—C4—O1	3.20 (19)	C10—N3—C9—C12	−178.94 (16)
C3^i—C1—C4—O2	3.24 (19)	C11—N4—C9—N3	−0.22 (18)
C2—C1—C4—O2	−174.66 (12)	C11—N4—C9—C12	179.09 (16)
N1—C6—C7—N2	0.4 (2)	C9—N3—C10—C11	−0.36 (18)
N2—C5—N1—C6	0.66 (18)	N3—C10—C11—N4	0.23 (19)
C8—C5—N1—C6	−178.92 (16)	C9—N4—C11—C10	−0.01 (19)
C7—C6—N1—C5	−0.7 (2)

Symmetry code: (i) −x, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···N3	0.88 (1)	1.83 (1)	2.7078 (18)	174 (2)
N2—H2A···O2	0.92 (2)	1.78 (2)	2.6965 (17)	175.6 (17)
O3—H3B···O1	0.74 (3)	2.08 (3)	2.8138 (18)	170 (3)
O4—H4B···O1	0.90 (3)	1.87 (3)	2.7723 (17)	175 (2)
O3—H3A···O2^ii	0.87 (3)	1.94 (3)	2.812 (2)	176 (3)
O4—H4A···O3^iii	0.81 (3)	1.97 (3)	2.766 (2)	166 (3)
N4—H4C···O4^iv	0.85 (2)	1.94 (2)	2.7872 (19)	175.7 (18)
C12—H12B···O3^v	0.96	2.59	3.542 (2)	169
C10—H10···Cg^vi	0.93	2.89	3.700 (2)	147

Symmetry codes: (ii) x+1, y, z; (iii) −x+1, −y, −z; (iv) −x, −y+1, −z−1; (v) x−1, y+1, z−1; (vi) x, y, z−1.