In the crystal structure of the title compound, C
7H
7N
2+·C
7H
5O
4−, the partially overlapped arrangement and the face-to-face separation of 3.557 (7) Å suggest π–π stacking between parallel benzimidazolium cations, and the C—H
Cg angle of 173° and H
Cg separation of 2.64 Å (where
Cg is the centroid of the benzene ring) suggest C—H
π stacking between the benzimidazolium cation and dihydroxybenzoate anion. Classical N—H
O and O—H
O and weak C—H
O hydrogen bonds consolidate the crystal structure.
Supporting information
CCDC reference: 296574
Key indicators
- Single-crystal X-ray study
- T = 295 K
- Mean (C-C) = 0.002 Å
- R factor = 0.041
- wR factor = 0.115
- Data-to-parameter ratio = 15.9
checkCIF/PLATON results
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Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ .... ?
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0 ALERT level B = Potentially serious problem
1 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
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CdCl2 (1 mmol), 3,5-dihydroxybenzoic acid (2 mmol), benzimidazole (2 mmol) and Na2CO3 (1 mmol) were dissolved in a water/ethanol solution (20 ml, 1:1). The mixture was refluxed for 2 h and filtered after cooling to room temperature. Single crystals of (I) were obtained from the filtrate after 10 d.
Hydroxy H atoms were located in a difference Fourier map and refined as riding in their as found relative positions (Table 2) with Uiso(H) = 1.2Ueq(O). Other H atoms were placed in calculated positions, with C—H = 0.93 Å and N—H = 0.86 Å, and refined as riding with Uiso(H) = 1.2Ueq(carrier).
Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Benzimidazolium 3,5-dihydroxybenzoate
top
Crystal data top
C7H7N2+·C7H5O4− | F(000) = 1136 |
Mr = 272.26 | Dx = 1.429 Mg m−3 |
Orthorhombic, Pbcn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2n 2ab | Cell parameters from 19663 reflections |
a = 16.297 (4) Å | θ = 3.1–27.0° |
b = 10.600 (3) Å | µ = 0.11 mm−1 |
c = 14.649 (5) Å | T = 295 K |
V = 2530.6 (13) Å3 | Chunk, brown |
Z = 8 | 0.40 × 0.38 × 0.36 mm |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 2435 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.037 |
Graphite monochromator | θmax = 27.5°, θmin = 3.1° |
Detector resolution: 10.00 pixels mm-1 | h = −21→20 |
ω scans | k = −13→13 |
23272 measured reflections | l = −19→19 |
2901 independent reflections | |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.041 | H-atom parameters constrained |
wR(F2) = 0.115 | w = 1/[σ2(Fo2) + (0.0603P)2 + 0.6188P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
2901 reflections | Δρmax = 0.35 e Å−3 |
182 parameters | Δρmin = −0.29 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0108 (10) |
Crystal data top
C7H7N2+·C7H5O4− | V = 2530.6 (13) Å3 |
Mr = 272.26 | Z = 8 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 16.297 (4) Å | µ = 0.11 mm−1 |
b = 10.600 (3) Å | T = 295 K |
c = 14.649 (5) Å | 0.40 × 0.38 × 0.36 mm |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 2435 reflections with I > 2σ(I) |
23272 measured reflections | Rint = 0.037 |
2901 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.115 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.35 e Å−3 |
2901 reflections | Δρmin = −0.29 e Å−3 |
182 parameters | |
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 | x | y | z | Uiso*/Ueq | |
N1 | 0.60250 (7) | 0.67812 (12) | 0.38616 (8) | 0.0372 (3) | |
H1 | 0.6548 | 0.6889 | 0.3865 | 0.045* | |
N2 | 0.47272 (7) | 0.71952 (11) | 0.38770 (9) | 0.0358 (3) | |
H2 | 0.4276 | 0.7616 | 0.3893 | 0.043* | |
O1 | 0.76817 (6) | 0.68278 (10) | 0.40383 (6) | 0.0347 (3) | |
O2 | 0.87168 (6) | 0.54682 (10) | 0.39438 (6) | 0.0361 (3) | |
O3 | 0.69620 (6) | 0.76955 (10) | 0.07692 (6) | 0.0353 (3) | |
H3A | 0.7080 | 0.7858 | 0.0162 | 0.042* | |
O4 | 0.91927 (5) | 0.47395 (9) | 0.06519 (6) | 0.0298 (2) | |
H4A | 0.9029 | 0.4645 | 0.0063 | 0.036* | |
C1 | 0.81810 (7) | 0.61482 (12) | 0.35910 (8) | 0.0243 (3) | |
C2 | 0.81354 (7) | 0.61852 (11) | 0.25632 (8) | 0.0235 (3) | |
C3 | 0.75700 (7) | 0.69565 (12) | 0.21238 (8) | 0.0258 (3) | |
H3 | 0.7220 | 0.7471 | 0.2460 | 0.031* | |
C4 | 0.75337 (7) | 0.69490 (12) | 0.11773 (8) | 0.0251 (3) | |
C5 | 0.80546 (7) | 0.61866 (12) | 0.06714 (8) | 0.0251 (3) | |
H5 | 0.8013 | 0.6166 | 0.0038 | 0.030* | |
C6 | 0.86403 (7) | 0.54516 (11) | 0.11161 (8) | 0.0236 (3) | |
C7 | 0.86756 (8) | 0.54453 (12) | 0.20633 (8) | 0.0256 (3) | |
H7 | 0.9061 | 0.4946 | 0.2362 | 0.031* | |
C8 | 0.54718 (9) | 0.76837 (14) | 0.39056 (10) | 0.0371 (3) | |
H8 | 0.5589 | 0.8540 | 0.3950 | 0.045* | |
C9 | 0.42092 (9) | 0.49446 (15) | 0.37746 (12) | 0.0448 (4) | |
H9 | 0.3650 | 0.5119 | 0.3778 | 0.054* | |
C10 | 0.45019 (11) | 0.37333 (16) | 0.37261 (14) | 0.0528 (4) | |
H10 | 0.4130 | 0.3070 | 0.3692 | 0.063* | |
C11 | 0.53357 (11) | 0.34662 (16) | 0.37268 (14) | 0.0558 (5) | |
H11 | 0.5505 | 0.2629 | 0.3700 | 0.067* | |
C12 | 0.59154 (10) | 0.43933 (15) | 0.37661 (13) | 0.0480 (4) | |
H12 | 0.6474 | 0.4210 | 0.3764 | 0.058* | |
C13 | 0.56263 (8) | 0.56282 (13) | 0.38097 (10) | 0.0337 (3) | |
C14 | 0.47905 (8) | 0.58925 (13) | 0.38177 (10) | 0.0328 (3) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0276 (6) | 0.0409 (7) | 0.0432 (7) | −0.0021 (5) | 0.0014 (5) | −0.0028 (5) |
N2 | 0.0310 (6) | 0.0313 (6) | 0.0451 (7) | 0.0048 (5) | −0.0001 (5) | −0.0023 (5) |
O1 | 0.0304 (5) | 0.0532 (6) | 0.0205 (4) | 0.0070 (4) | 0.0010 (3) | −0.0083 (4) |
O2 | 0.0465 (6) | 0.0426 (6) | 0.0192 (4) | 0.0126 (4) | −0.0022 (4) | 0.0037 (4) |
O3 | 0.0317 (5) | 0.0494 (6) | 0.0247 (5) | 0.0147 (4) | 0.0020 (4) | 0.0104 (4) |
O4 | 0.0354 (5) | 0.0339 (5) | 0.0202 (4) | 0.0089 (4) | 0.0015 (3) | −0.0032 (4) |
C1 | 0.0261 (6) | 0.0289 (6) | 0.0180 (6) | −0.0024 (5) | 0.0001 (4) | −0.0003 (5) |
C2 | 0.0262 (6) | 0.0264 (6) | 0.0179 (6) | −0.0008 (5) | −0.0001 (4) | 0.0005 (4) |
C3 | 0.0257 (6) | 0.0299 (6) | 0.0219 (6) | 0.0037 (5) | 0.0027 (4) | −0.0003 (5) |
C4 | 0.0223 (6) | 0.0304 (6) | 0.0227 (6) | 0.0013 (5) | −0.0013 (4) | 0.0048 (5) |
C5 | 0.0291 (6) | 0.0304 (6) | 0.0159 (5) | −0.0007 (5) | −0.0013 (4) | 0.0017 (5) |
C6 | 0.0259 (6) | 0.0235 (6) | 0.0213 (6) | −0.0001 (4) | 0.0023 (4) | −0.0013 (4) |
C7 | 0.0300 (6) | 0.0272 (6) | 0.0195 (6) | 0.0051 (5) | −0.0020 (4) | 0.0012 (5) |
C8 | 0.0395 (7) | 0.0325 (7) | 0.0393 (8) | −0.0018 (6) | 0.0001 (6) | −0.0017 (6) |
C9 | 0.0347 (7) | 0.0406 (9) | 0.0590 (11) | −0.0034 (6) | 0.0014 (7) | −0.0045 (7) |
C10 | 0.0541 (10) | 0.0349 (8) | 0.0694 (12) | −0.0073 (7) | 0.0026 (8) | −0.0062 (8) |
C11 | 0.0639 (11) | 0.0318 (8) | 0.0718 (13) | 0.0105 (7) | 0.0034 (9) | −0.0059 (8) |
C12 | 0.0419 (8) | 0.0432 (9) | 0.0590 (11) | 0.0146 (7) | 0.0010 (7) | −0.0049 (8) |
C13 | 0.0313 (7) | 0.0352 (8) | 0.0346 (7) | 0.0026 (5) | 0.0014 (5) | −0.0033 (6) |
C14 | 0.0318 (7) | 0.0315 (7) | 0.0351 (7) | 0.0043 (5) | 0.0014 (5) | −0.0026 (5) |
Geometric parameters (Å, º) top
N1—C8 | 1.3160 (19) | C4—C5 | 1.3867 (17) |
N1—C13 | 1.3862 (19) | C5—C6 | 1.3937 (17) |
N1—H1 | 0.8600 | C5—H5 | 0.9300 |
N2—C8 | 1.3200 (18) | C6—C7 | 1.3888 (17) |
N2—C14 | 1.3875 (19) | C7—H7 | 0.9300 |
N2—H2 | 0.8600 | C8—H8 | 0.9300 |
O1—C1 | 1.2690 (15) | C9—C10 | 1.372 (2) |
O2—C1 | 1.2445 (15) | C9—C14 | 1.382 (2) |
O3—C4 | 1.3607 (14) | C9—H9 | 0.9300 |
O3—H3A | 0.9261 | C10—C11 | 1.388 (3) |
O4—C6 | 1.3573 (14) | C10—H10 | 0.9300 |
O4—H4A | 0.9084 | C11—C12 | 1.364 (3) |
C1—C2 | 1.5079 (17) | C11—H11 | 0.9300 |
C2—C7 | 1.3879 (17) | C12—C13 | 1.393 (2) |
C2—C3 | 1.3899 (16) | C12—H12 | 0.9300 |
C3—C4 | 1.3877 (17) | C13—C14 | 1.3905 (19) |
C3—H3 | 0.9300 | | |
| | | |
C8—N1—C13 | 108.82 (12) | C7—C6—C5 | 119.87 (11) |
C8—N1—H1 | 125.6 | C2—C7—C6 | 119.88 (11) |
C13—N1—H1 | 125.6 | C2—C7—H7 | 120.1 |
C8—N2—C14 | 108.91 (12) | C6—C7—H7 | 120.1 |
C8—N2—H2 | 125.5 | N1—C8—N2 | 110.06 (13) |
C14—N2—H2 | 125.5 | N1—C8—H8 | 125.0 |
C4—O3—H3A | 112.8 | N2—C8—H8 | 125.0 |
C6—O4—H4A | 110.1 | C10—C9—C14 | 116.38 (14) |
O2—C1—O1 | 124.35 (12) | C10—C9—H9 | 121.8 |
O2—C1—C2 | 117.66 (11) | C14—C9—H9 | 121.8 |
O1—C1—C2 | 117.97 (10) | C9—C10—C11 | 122.10 (16) |
C7—C2—C3 | 120.56 (11) | C9—C10—H10 | 119.0 |
C7—C2—C1 | 118.74 (10) | C11—C10—H10 | 119.0 |
C3—C2—C1 | 120.69 (10) | C12—C11—C10 | 122.07 (16) |
C4—C3—C2 | 119.19 (11) | C12—C11—H11 | 119.0 |
C4—C3—H3 | 120.4 | C10—C11—H11 | 119.0 |
C2—C3—H3 | 120.4 | C11—C12—C13 | 116.40 (15) |
O3—C4—C5 | 121.55 (11) | C11—C12—H12 | 121.8 |
O3—C4—C3 | 117.70 (11) | C13—C12—H12 | 121.8 |
C5—C4—C3 | 120.74 (11) | N1—C13—C14 | 106.32 (12) |
C4—C5—C6 | 119.69 (11) | N1—C13—C12 | 132.27 (14) |
C4—C5—H5 | 120.2 | C14—C13—C12 | 121.41 (14) |
C6—C5—H5 | 120.2 | C9—C14—N2 | 132.47 (13) |
O4—C6—C7 | 118.06 (11) | C9—C14—C13 | 121.63 (13) |
O4—C6—C5 | 122.07 (11) | N2—C14—C13 | 105.89 (12) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 | 1.87 | 2.7128 (18) | 168 |
N2—H2···O3i | 0.86 | 2.08 | 2.8510 (18) | 149 |
O3—H3A···O1ii | 0.93 | 1.72 | 2.6499 (16) | 179 |
O4—H4A···O2iii | 0.91 | 1.72 | 2.6289 (15) | 178 |
C8—H8···O2iv | 0.93 | 2.34 | 3.235 (2) | 162 |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+3/2, −y+3/2, z−1/2; (iii) x, −y+1, z−1/2; (iv) −x+3/2, y+1/2, z. |
Experimental details
Crystal data |
Chemical formula | C7H7N2+·C7H5O4− |
Mr | 272.26 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 295 |
a, b, c (Å) | 16.297 (4), 10.600 (3), 14.649 (5) |
V (Å3) | 2530.6 (13) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.40 × 0.38 × 0.36 |
|
Data collection |
Diffractometer | Rigaku R-AXIS RAPID diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 23272, 2901, 2435 |
Rint | 0.037 |
(sin θ/λ)max (Å−1) | 0.650 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.115, 1.09 |
No. of reflections | 2901 |
No. of parameters | 182 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.35, −0.29 |
Selected bond lengths (Å) topN1—C8 | 1.3160 (19) | O1—C1 | 1.2690 (15) |
N1—C13 | 1.3862 (19) | O2—C1 | 1.2445 (15) |
N2—C8 | 1.3200 (18) | O3—C4 | 1.3607 (14) |
N2—C14 | 1.3875 (19) | O4—C6 | 1.3573 (14) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 | 1.87 | 2.7128 (18) | 168 |
N2—H2···O3i | 0.86 | 2.08 | 2.8510 (18) | 149 |
O3—H3A···O1ii | 0.93 | 1.72 | 2.6499 (16) | 179 |
O4—H4A···O2iii | 0.91 | 1.72 | 2.6289 (15) | 178 |
C8—H8···O2iv | 0.93 | 2.34 | 3.235 (2) | 162 |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+3/2, −y+3/2, z−1/2; (iii) x, −y+1, z−1/2; (iv) −x+3/2, y+1/2, z. |
We have been interested in the nature of aromatic stacking in complexes for several years (Chen et al., 2003; Pan & Xu, 2004; Li et al., 2005) because aromatic stacking is an important intermolecular non-covalent interaction which correlates with electron transfer in some biological systems (Deisenhofer & Michel, 1989). We present here the structure of the title compound, (I), which contains both benzene and benzimidazol aromatic ring systems.
The molecule of (I) consists of a benzimidazolium (bzim) cation and a dihydroxybenzoate (dhba) anion (Fig. 1). The carboxyl group of dhba is coplanar with the benzene ring [dihedral angle 1.05 (9)°]. The smaller difference of 0.025 (2) Å between the C1—O1 and C1—O2 bond distances (Table 1) is consistent with the value of 0.022 (4) Å found in piperazinium bis(3,5-dihydroxybenzoate) (Burchell et al., 2001) and indicates the deprotonation of the carboxyl group.
Approximately symmetric N—C bonds are observed in the protonated bzim cation; the differences between the N1—C8 and N2—C8 bond distances and between the N1—C13 and N2—C14 bond distances are smaller than twice the standard uncertainties (Table 1).
A partially overlapped arrangement is observed between parallel N1-bzim and N1vi-bzim cations [symmetry code: (vi) −x + 1, −y + 1, −z + 1] (Fig. 2). The face-to-face distances of 3.557 (7) Å suggest the existence of π–π stacking. C—H···π stacking is observed between bzim and dhba (Fig. 1), the C10—H10···Cg angle and H···Cg separation being 173° and 2.64 Å, respectively, where Cg is the centroid of the C2v-containing benzene ring [symmetry code: (v) x − 1/2, y − 1/2, −z + 1/2].
Classical N—H···O and O—H···O and weak C—H···O hydrogen bonds occur (Table 2), consolidating the crystal structure of (I).