Bisimidazolium terephthalate

The formula unit of the title compound, 2C₃H₅N₂⁺·C₈H₄O₄²⁻, consists of two imidazole cations which are N—H...O hydrogen-bonded to a terephthalate anion which lies on a crystallographic inversion center. In the crystal structure, two N—H...O and two C—H...O hydrogen bonds link the components into a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.046
• wR factor = 0.137
• Data-to-parameter ratio = 15.7

checkCIF/PLATON results

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Alert level C
PLAT153_ALERT_1_C The su's on the Cell Axes   are Equal (x 100000)         60 Ang.
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.46
PLAT353_ALERT_3_C Long    N-H Bond (0.87A)   N1     -   H1     ...       1.05 Ang.
PLAT353_ALERT_3_C Long    N-H Bond (0.87A)   N2     -   H2A    ...       1.01 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

With the aim of researching hydrogen-bonded actions in new classes of organic adducts, we have investigated the reactions of terephthalic acid with imidazole. The 1:2 organic salt is formed as a consequence of protons being transferred from the carboxyl oxygen atoms to the imine N atoms. We report here the molecular and supramolecular structure of the title compound.

The asymmetric unit consists of half of a terephthalate anion and one imidazolium cation, the formula unit being generated by a crystallogrphic inversion center (Fig.1). The supramolecular structure can be readily analysed in terms of simple substructures listed below. Firstly, a combination of the N1–H1···O1ⁱⁱⁱ [N–O = 2.6336 (14) Å, N–H···O = 167.1 (17)°, symmetry code: (iii) -x + 1/2, y + 1/2, -z + 3/2] and N2–H2···O2 hydrogen bonds (Table 1) links the terephthalate anion and imidazolium cations into a (30–1) sheet (Fig.2) in the form of a (6,6) net (Batten & Robson, 1998) which is built from R₈⁸(22) rings (Bernstein et al., 1995). Three networks of this type pass through the unit cell by translation. Secondly, the imidazolium C5 and C6 atoms at (x,y,z) act as soft hydrogen-bond donor, via. H5A and H6A, to the carboxyl O2 and O1 atoms at (1 - x, -y, 1 - z) and (-x, -y, 1 - z), respectively, linking the adjacent networks into a simple three-dimensional network (Fig.3). Although aryl and imidazole rings exist, no π–π stacking and C–H···π interactions are observed in the supramolecular structure.

Related literature

For related literature, see: Bernstein et al. (1995); Batten & Robson (1998)

S2. Experimental

All reagents and solvents were used as obtained without further purification. 1:2 molar amount of imidazole (0.4 mmol, 27 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, and U_iso(H) = 1.2U_eq(C). H1 and H2A were located from the difference maps with the N–H distances refined freely and their U_iso values being set 1.2 times of their carrier atoms.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (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 symmetry position (-x, -y, -z).
	Fig. 2. Part of the crystal structure, showing the formation of the two-dimensional (301¯) network fromed by N–H···O hydrogen bonds. Hydrogen bonds are shown as dashed lines. Atom marked with (iii) is at symmetry position (-x + 1/2, y + 1/2, -z + 3/2).
	Fig. 3. Part of the crystal structure, showing the formation of the three-dimensional network formed by C–H···O and N–H···O hydrogen bonds. Hydrogen bonds are shown as dashed lines.

Bisimidazolium terephthalate

Crystal data

2C3H5N2^+·C8H4O4^2^−	F(000) = 316
Mr = 302.29	Dx = 1.392 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3264 reflections
a = 9.6288 (6) Å	θ = 2.3–28.1°
b = 8.3351 (6) Å	µ = 0.11 mm^−1
c = 9.8244 (6) Å	T = 298 K
β = 113.854 (1)°	Block, colorless
V = 721.12 (8) Å^3	0.30 × 0.20 × 0.20 mm
Z = 2

Data collection

Bruker SMART APEX CCD area-detector diffractometer	1696 independent reflections
Radiation source: fine focus sealed Siemens Mo tube	1368 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
0.3° wide ω exposures scans	θmax = 28.0°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −12→12
Tmin = 0.966, Tmax = 0.979	k = −10→10
7596 measured reflections	l = −11→12

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.137	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0835P)^2 + 0.0143P] where P = (Fo^2 + 2Fc^2)/3
1696 reflections	(Δ/σ)max < 0.001
108 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

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	0.05078 (13)	−0.03576 (14)	0.15160 (12)	0.0333 (3)
C2	−0.05484 (15)	−0.13358 (15)	0.04568 (13)	0.0382 (3)
H2	−0.0920	−0.2237	0.0757	0.046*
C3	−0.10550 (14)	−0.09803 (15)	−0.10470 (13)	0.0372 (3)
H3	−0.1766	−0.1643	−0.1746	0.045*
C4	0.10569 (15)	−0.07248 (15)	0.31591 (13)	0.0370 (3)
O1	0.02858 (11)	−0.17027 (15)	0.35300 (10)	0.0590 (4)
O2	0.22390 (11)	−0.00486 (13)	0.40159 (9)	0.0511 (3)
C5	0.52371 (16)	0.05999 (17)	0.75057 (15)	0.0464 (4)
H5A	0.5859	0.0091	0.7120	0.056*
C6	0.32334 (17)	0.15446 (19)	0.77332 (15)	0.0505 (4)
H6A	0.2231	0.1806	0.7535	0.061*
C7	0.56890 (16)	0.13368 (18)	0.88368 (15)	0.0484 (4)
H7A	0.6682	0.1432	0.9542	0.058*
N1	0.44244 (13)	0.19155 (15)	0.89584 (12)	0.0483 (3)
H1	0.438 (2)	0.251 (2)	0.988 (2)	0.084 (6)*
N2	0.36978 (14)	0.07411 (14)	0.68328 (12)	0.0452 (3)
H2A	0.3003 (19)	0.027 (2)	0.584 (2)	0.068 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0375 (6)	0.0407 (6)	0.0203 (6)	0.0038 (5)	0.0103 (5)	0.0013 (4)
C2	0.0470 (7)	0.0409 (6)	0.0259 (6)	−0.0047 (5)	0.0140 (6)	0.0027 (5)
C3	0.0432 (7)	0.0422 (7)	0.0220 (6)	−0.0057 (5)	0.0089 (5)	−0.0036 (5)
C4	0.0412 (7)	0.0474 (7)	0.0218 (6)	0.0086 (5)	0.0120 (5)	0.0031 (5)
O1	0.0588 (7)	0.0867 (8)	0.0293 (6)	−0.0078 (5)	0.0154 (5)	0.0186 (5)
O2	0.0526 (6)	0.0717 (7)	0.0207 (5)	−0.0033 (5)	0.0062 (4)	−0.0042 (4)
C5	0.0489 (8)	0.0550 (8)	0.0367 (8)	−0.0012 (6)	0.0189 (6)	−0.0082 (6)
C6	0.0468 (8)	0.0713 (10)	0.0318 (7)	0.0022 (7)	0.0141 (6)	−0.0073 (6)
C7	0.0454 (8)	0.0611 (8)	0.0340 (8)	−0.0049 (6)	0.0112 (6)	−0.0068 (6)
N1	0.0541 (7)	0.0623 (7)	0.0271 (6)	−0.0010 (6)	0.0149 (5)	−0.0097 (5)
N2	0.0517 (7)	0.0557 (7)	0.0258 (6)	−0.0048 (5)	0.0132 (5)	−0.0074 (5)

Geometric parameters (Å, º)

C1—C2	1.3878 (17)	C5—N2	1.3621 (19)
C1—C3^i	1.3892 (17)	C5—H5A	0.9300
C1—C4	1.5128 (16)	C6—N1	1.3203 (17)
C2—C3	1.3877 (16)	C6—N2	1.3232 (17)
C2—H2	0.9300	C6—H6A	0.9300
C3—C1^i	1.3892 (17)	C7—N1	1.3592 (17)
C3—H3	0.9300	C7—H7A	0.9300
C4—O2	1.2437 (16)	N1—H1	1.04 (2)
C4—O1	1.2518 (16)	N2—H2A	1.010 (18)
C5—C7	1.3478 (19)
C2—C1—C3^i	118.96 (11)	C7—C5—H5A	126.5
C2—C1—C4	121.01 (11)	N2—C5—H5A	126.5
C3^i—C1—C4	120.03 (11)	N1—C6—N2	108.92 (13)
C3—C2—C1	120.56 (12)	N1—C6—H6A	125.5
C3—C2—H2	119.7	N2—C6—H6A	125.5
C1—C2—H2	119.7	C5—C7—N1	107.33 (12)
C2—C3—C1^i	120.49 (11)	C5—C7—H7A	126.3
C2—C3—H3	119.8	N1—C7—H7A	126.3
C1^i—C3—H3	119.8	C6—N1—C7	108.39 (12)
O2—C4—O1	125.89 (12)	C6—N1—H1	125.2 (11)
O2—C4—C1	117.37 (12)	C7—N1—H1	126.3 (11)
O1—C4—C1	116.73 (11)	C6—N2—C5	108.35 (12)
C4—O2—H2A	133.4 (6)	C6—N2—H2A	124.6 (9)
C7—C5—N2	107.01 (12)	C5—N2—H2A	126.9 (9)
C3^i—C1—C2—C3	−0.2 (2)	O1—C4—O2—H2A	−18.7 (8)
C4—C1—C2—C3	179.41 (10)	C1—C4—O2—H2A	162.3 (8)
C1—C2—C3—C1^i	0.3 (2)	N2—C5—C7—N1	0.01 (16)
C2—C1—C4—O2	163.41 (12)	N2—C6—N1—C7	0.20 (18)
C3^i—C1—C4—O2	−16.93 (18)	C5—C7—N1—C6	−0.13 (18)
C2—C1—C4—O1	−15.68 (18)	N1—C6—N2—C5	−0.19 (17)
C3^i—C1—C4—O1	163.98 (12)	C7—C5—N2—C6	0.11 (16)

Symmetry code: (i) −x, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O2	1.010 (18)	1.665 (19)	2.6307 (14)	158.6 (15)
C6—H6A···O1^ii	0.93	2.22	3.1046 (18)	159
C5—H5A···O2^iii	0.93	2.50	3.3601 (17)	154
N1—H1···O1^iv	1.04 (2)	1.61 (2)	2.6336 (14)	167.1 (17)

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