Benzoic acid–2,2′-biimidazole (2/1)

In the title compound, C₆H₆N₄·2C₇H₆O₂, the asymmetric unit contains a half-mol­ecule of biimidazole and one benzoic acid mol­ecule. The unit cell contains two biimidazole mol­ecules and four benzoic acid mol­ecules, giving the reported 2:1 ratio of benzoic acid to biimidazole. The biimidazole mol­ecule is located on an inversion center (passing through the central C—C bond). Strong N—H...O and O—H...N hydrogen bonds link the benzoic acid mol­ecules with the neutral biimidazole mol­ecules, which lie in planar sheets. In the crystal packing, the parallel sheets are related by a twofold rotation axis and an inversion centre, respectively, forming an inter­woven three-dimensional network via weak C=O...π inter­molecular inter­actions between neighboring mol­ecules.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.098
• wR factor = 0.188
• Data-to-parameter ratio = 11.8

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT340_ALERT_3_C Low Bond Precision on  C-C Bonds (x 1000) Ang ..          7
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.595         63
PLAT481_ALERT_4_C Long D...A H-Bond Reported C4     ..  CG1     ..       4.39 Ang.

Alert level G
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 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
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Compounds containing the 2,2'-biimidazole moiety have been the focus of several investigations not only due to their biological activity, but also due to their contribution to the field of crystal engineering (Matthews, et al. 1990; Tadokoro & Nakasuji, 2000). In these compunds weak interactions, such as C—H···O and C=O···π, play crucial roles in building the overall three-dimensional structure (Mori & Miyoshi, 2004; Li & Yang, 2006; Gao et al., 2009).

The asymmetric unit of compound (I) contains one benzoic acid and 1/2 neutral biimidazole molecule, in which the imidazole rings are coplanar (Fig. 1). Each biimidazole molecule is linked to two benzoic acids via strong N—H···O and O—H···N hydrogen bonds (Table 1) twithin planar sheets (Figure 2). These sheets further assemble to layers via weak C=O···π (see Table 1, Cg1 for centre of N1/C1/N2/C3/C2) interactions between neighboring molecules and arrange alternatively and across along b and c axis in two-dimensional structure, and the dihedral angle of the planes are 92.7°. In contrast, two groups of these parallel layers on a twofold rotation axis and inversion centre forming a zigzag conformation along c axis in whole three-dimensional network as shown in Fig. 3.

Related literature

For background to the use of 2,2'-biimidazoles in crystal engineering, see: Matthews et al. (1990); Tadokoro & Nakasuji (2000). For similar structures, see: Gao et al. (2009); Li & Yang (2006); Mori & Miyoshi (2004).

S2. Experimental

Benzoic acid (0.25 g, 2 mmol) and biimidazole (1 mmol) were dissolved in water(10 ml) by adding 1.4 ml of 2 M HCl while stirring. The solutions were stirred for 1 h, then filtered. Filtrate was left to stand at room temperature. Crystals suitable for data collection appeared after a few weeks by slow evaporation of the aqueous solvent.

S3. Refinement

H atoms attached to C atoms were placed in geometrically idealized positions, with Csp² = 0.93 Å, and constrained to ride on their carrier atoms, with U_iso(H) = 1.2_Ueq(C). H atoms attached to N1 and O1 atoms were located in difference Fourier maps and refined with U_iso(H for N) = 0.06 Ų and U_iso(H) = 1.5_Ueq(O); N—H distance is 0.88 (5) Å and the O—H distance is 0.856 Å.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and SHELXL97 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL/PC (Sheldrick, 2008).

Figures

	Fig. 1. A view of the structure of compound (I) with displacement ellipsoids drawn at the 50% probability level, the biimidazole sits on a center of symmetry passing through the C1—C1 bond. Symmetry code: (i) 1 - x, 1 - y, 1 - z.
	Fig. 2. H-bonds (dotting line) in (I). Symmetry codes: (ii) x, 1 + y, z; (iv) 1 - x, -y, 1 - z; (v) 1 - x, 1 - y, 1 - z.
	Fig. 3. The packing view in the title compound (I), dotting line for H-bonds.

Benzoic acid–2,2'-biimidazole (2/1)

Crystal data

C6H6N4·2C7H6O2	F(000) = 396
Mr = 378.38	Dx = 1.367 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 698 reflections
a = 11.232 (5) Å	θ = 2.5–20.8°
b = 5.082 (2) Å	µ = 0.10 mm^−1
c = 16.342 (7) Å	T = 298 K
β = 99.832 (6)°	Block, colorless
V = 919.2 (7) Å^3	0.40 × 0.20 × 0.10 mm
Z = 2

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1550 independent reflections
Radiation source: fine-focus sealed tube	1243 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
ω scans	θmax = 25.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	h = −13→12
Tmin = 0.962, Tmax = 0.990	k = −6→2
3367 measured reflections	l = −19→19

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)] = 0.098	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.188	H atoms treated by a mixture of independent and constrained refinement
S = 1.25	w = 1/[σ^2(Fo^2) + (0.0425P)^2 + 1.0781P] where P = (Fo^2 + 2Fc^2)/3
1550 reflections	(Δ/σ)max < 0.001
131 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.19 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
N1	0.3655 (3)	0.6966 (8)	0.4607 (2)	0.0406 (10)
H1	0.383 (4)	0.809 (10)	0.423 (3)	0.064 (17)*
N2	0.3784 (3)	0.3740 (7)	0.5510 (2)	0.0389 (9)
C1	0.4360 (4)	0.5176 (8)	0.5031 (2)	0.0307 (10)
C2	0.2533 (4)	0.6694 (10)	0.4821 (3)	0.0436 (12)
H2	0.1846	0.7679	0.4624	0.052*
C3	0.2630 (4)	0.4717 (10)	0.5372 (3)	0.0453 (12)
H3	0.2003	0.4097	0.5625	0.054*
C4	0.4969 (4)	0.1219 (9)	0.3172 (3)	0.0376 (11)
C5	0.4964 (4)	0.3271 (9)	0.2521 (2)	0.0347 (10)
C6	0.5982 (4)	0.3745 (10)	0.2158 (3)	0.0451 (12)
H6	0.6687	0.2790	0.2329	0.054*
C7	0.5946 (4)	0.5616 (10)	0.1549 (3)	0.0516 (13)
H7	0.6625	0.5916	0.1308	0.062*
C8	0.4913 (4)	0.7050 (10)	0.1294 (3)	0.0491 (13)
H8	0.4897	0.8321	0.0883	0.059*
C9	0.3913 (4)	0.6618 (10)	0.1641 (3)	0.0458 (12)
H9	0.3216	0.7595	0.1468	0.055*
C10	0.3934 (4)	0.4739 (10)	0.2247 (3)	0.0441 (12)
H10	0.3244	0.4447	0.2478	0.053*
O1	0.5977 (3)	−0.0029 (7)	0.3367 (2)	0.0532 (10)
H1A	0.5971	−0.1186	0.3747	0.080*
O2	0.4086 (3)	0.0801 (7)	0.3491 (2)	0.0517 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.043 (2)	0.037 (2)	0.042 (2)	−0.0004 (19)	0.0097 (18)	0.009 (2)
N2	0.041 (2)	0.035 (2)	0.043 (2)	−0.0011 (18)	0.0116 (17)	0.0088 (19)
C1	0.044 (2)	0.022 (2)	0.027 (2)	0.003 (2)	0.0077 (19)	0.0055 (19)
C2	0.037 (3)	0.048 (3)	0.046 (3)	0.004 (2)	0.007 (2)	0.000 (3)
C3	0.032 (2)	0.057 (3)	0.048 (3)	0.000 (2)	0.009 (2)	0.011 (3)
C4	0.041 (3)	0.029 (2)	0.043 (3)	−0.004 (2)	0.009 (2)	−0.002 (2)
C5	0.038 (2)	0.032 (3)	0.034 (2)	−0.004 (2)	0.0064 (19)	−0.005 (2)
C6	0.037 (3)	0.046 (3)	0.053 (3)	0.002 (2)	0.012 (2)	0.008 (3)
C7	0.048 (3)	0.052 (3)	0.060 (3)	−0.001 (3)	0.024 (2)	0.013 (3)
C8	0.051 (3)	0.048 (3)	0.049 (3)	−0.003 (3)	0.008 (2)	0.013 (3)
C9	0.036 (3)	0.046 (3)	0.054 (3)	0.006 (2)	0.004 (2)	0.009 (3)
C10	0.033 (2)	0.055 (3)	0.046 (3)	−0.005 (2)	0.013 (2)	0.002 (3)
O1	0.0371 (17)	0.058 (2)	0.065 (2)	0.0067 (18)	0.0089 (15)	0.0244 (19)
O2	0.0465 (19)	0.051 (2)	0.063 (2)	0.0094 (17)	0.0220 (16)	0.0155 (18)

Geometric parameters (Å, º)

N1—C1	1.322 (5)	C5—C10	1.385 (6)
N1—C2	1.371 (5)	C5—C6	1.397 (6)
N1—H1	0.88 (5)	C6—C7	1.371 (6)
N2—C1	1.319 (5)	C6—H6	0.9300
N2—C3	1.370 (5)	C7—C8	1.374 (6)
C1—C1^i	1.469 (8)	C7—H7	0.9300
C2—C3	1.342 (6)	C8—C9	1.359 (6)
C2—H2	0.9300	C8—H8	0.9300
C3—H3	0.9300	C9—C10	1.373 (6)
C4—O2	1.216 (5)	C9—H9	0.9300
C4—O1	1.289 (5)	C10—H10	0.9300
C4—C5	1.489 (6)	O1—H1A	0.8564
C1—N1—C2	106.9 (4)	C6—C5—C4	121.4 (4)
C1—N1—H1	129 (3)	C7—C6—C5	120.1 (4)
C2—N1—H1	124 (3)	C7—C6—H6	119.9
C1—N2—C3	104.4 (4)	C5—C6—H6	119.9
N2—C1—N1	112.4 (4)	C6—C7—C8	120.5 (4)
N2—C1—C1^i	124.0 (5)	C6—C7—H7	119.8
N1—C1—C1^i	123.6 (5)	C8—C7—H7	119.8
C3—C2—N1	105.9 (4)	C9—C8—C7	120.2 (5)
C3—C2—H2	127.0	C9—C8—H8	119.9
N1—C2—H2	127.0	C7—C8—H8	119.9
C2—C3—N2	110.4 (4)	C8—C9—C10	120.0 (4)
C2—C3—H3	124.8	C8—C9—H9	120.0
N2—C3—H3	124.8	C10—C9—H9	120.0
O2—C4—O1	123.6 (4)	C9—C10—C5	121.2 (4)
O2—C4—C5	121.7 (4)	C9—C10—H10	119.4
O1—C4—C5	114.7 (4)	C5—C10—H10	119.4
C10—C5—C6	118.0 (4)	C4—O1—H1A	113.7
C10—C5—C4	120.6 (4)
C3—N2—C1—N1	0.0 (5)	O1—C4—C5—C6	0.5 (6)
C3—N2—C1—C1^i	−179.6 (5)	C10—C5—C6—C7	0.0 (7)
C2—N1—C1—N2	0.0 (5)	C4—C5—C6—C7	178.9 (4)
C2—N1—C1—C1^i	179.6 (5)	C5—C6—C7—C8	0.4 (7)
C1—N1—C2—C3	0.0 (5)	C6—C7—C8—C9	−0.3 (8)
N1—C2—C3—N2	0.0 (5)	C7—C8—C9—C10	−0.1 (7)
C1—N2—C3—C2	0.0 (5)	C8—C9—C10—C5	0.5 (7)
O2—C4—C5—C10	−1.3 (6)	C6—C5—C10—C9	−0.4 (7)
O1—C4—C5—C10	179.3 (4)	C4—C5—C10—C9	−179.3 (4)
O2—C4—C5—C6	179.8 (4)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

Cg1 is the centroid of the [please define] ring.

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···N2^ii	0.86	1.77	2.613 (5)	170
N1—H1···O2^iii	0.88 (5)	1.89 (5)	2.767 (5)	173 (5)
C4—O2···Cg1	1.22 (1)	3.67 (1)	4.388 (2)	118 (1)

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