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The 2,2′-biimidazol-1-ium trichloro­acetate ion pairs in the title compound, C6H7N4+·C2Cl3O2, are held together by two N—H...O hydrogen bonds, and two adjacent ion pairs are linked into a centrosymmetric dimer by a pair of N—H...N hydrogen bonds. The hydrogen-bonding pattern can be described in graph-set motif notation as R22(9) and R22(10). Moreover, the adjacent dimers are associated by π–π inter­actions between five-membered rings of the 2,2′-biimidazol-1-ium cations [at (x, y, z) and (2 − x, −y, 1 − z)], with the ring centroids separated by 3.861 (1) Å, forming a ribbon-like supramolecular array along the b axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805029004/wk6059sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536805029004/wk6059Isup2.hkl
Contains datablock I

CCDC reference: 287741

Key indicators

  • Single-crystal X-ray study
  • T = 298 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.055
  • wR factor = 0.123
  • Data-to-parameter ratio = 13.1

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT242_ALERT_2_C Check Low Ueq as Compared to Neighbors for C7 PLAT242_ALERT_2_C Check Low Ueq as Compared to Neighbors for C8 PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor .... 2.08 PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor .... 2.14 PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ... 5 PLAT431_ALERT_2_C Short Inter HL..A Contact Cl2 .. O1 .. 3.15 Ang. PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd. # 2 C2 Cl3 O2
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 7 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 5 ALERT type 2 Indicator that the structure model may be wrong or deficient 1 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion

Comment top

2,2'-Biimidazole, H2biim, is not only a proton donor, but also a proton acceptor, so that it possesses five possible forms, i.e. di-deprotonated (dianion, biim2−), mono-deprotonated (monoanion, Hbiim), neutral (neutral, H2biim), mono-protonated (monocation, H3biim+) and di-protonated (dication, H4biim2+). Therefore, H2biim is a excellent candidate for the development of supramolecular motifs in crystals, and homomeric hydrogen-bonded motifs R22(10) (Cromer et al., 1987), heteromeric hydrogen-bonded motifs R22(9) (Ye et al., 2005) and R21(7) (Belanger & Beauchamp, 1996), and mixed hydrogen-bonded motifs R22(10) and R21(7) (Ramirez et al., 2002), have been structurally reported. In order to extend this research, the crystal structure of the title compound, C6H7N4+.C2Cl3O2, (I), is reported here.

The bond distances and angles of the mono-protonated H3biim+ in (I) are unexceptional and compare well with the values in neutral H2biim (Cromer et al., 1987) (Table 1 and Fig. 1). The two rings are almost coplanar in both cases. The dihedral angle between the two five-membered rings in neutral H2biim is 4.6°, and is slightly smaller in (I) at 4.47 (3)°.

Two N—H···O hydrogen bonds connect the H3biim+ cations and trichloroacetate anions to produce ion pairs, and two adjacent ion pairs are linked into a dimer by a third N3—H3A···N2i hydrogen bond [Table 2; symmetry code: (i) 2 − x, 1 − y, 1 − z]. The hydrogen-bonding pattern, as shown in Fig. 2, can be described in graph-set motifs (Etter, 1990; Grell et al., 2000) as R22(9) and R22(10). Adjacent dimers are associated by ππ interactions between the five-membered rings of the H3biim+ moieties [at (x, y, z) and (2 − x, −y, 1 − z)], with the ring centroids separated by 3.861 (1) Å, forming a ribbon-like supramolecular array along the b axis (Fig. 3).

Experimental top

2,2'-Biimidazole (2 mmol, 0.28 g) was suspended in water (30 ml). To the resulting suspension, concentrated aqueous trichloroacetic acid was added until the suspension became clear. The resulting solution was filtered and allowed to evaporate slowly at room temperature. After three weeks, colourless crystals of (I) appeared.

Refinement top

The H atoms of all N atoms were located from difference density maps and refined, with N—H distances restrained to 0.85 (2) Å, and with Uiso(H) = 1.2Ueq(N). The other H atoms were positioned geometrically and allowed to ride on their parent atoms at distances of Csp2—H = 0.93 Å and with Uiso(H) = 1.2Ueq(parent atom).

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2002); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The ion pair of (I), with the atom numbering, showing displacement ellipsoids at the 50% probability level.
[Figure 2] Fig. 2. The R22(9) and R22(10) hydrogen-bonding motifs in (I), formed by N—H···O and N—H···N hydrogen-bond interactions, which are shown as dashed lines. [Symmetry code: (i) 2 − x, 1 − y, 1 − z.]
[Figure 3] Fig. 3. A perspective view, along the b axis, of the supramolecular array in (I).
2,2'-Biimidazol-1-ium trichloroacetate top
Crystal data top
C6H7N4+·C2Cl3O2F(000) = 600
Mr = 297.53Dx = 1.679 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 1438 reflections
a = 12.4010 (13) Åθ = 2.6–24.2°
b = 5.5664 (6) ŵ = 0.77 mm1
c = 17.3648 (18) ÅT = 298 K
β = 100.858 (2)°Block, colourless
V = 1177.2 (2) Å30.31 × 0.13 × 0.12 mm
Z = 4
Data collection top
Bruker APEX area-detector
diffractometer
2129 independent reflections
Radiation source: fine-focus sealed tube1812 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.031
ϕ and ω scansθmax = 25.3°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
h = 1414
Tmin = 0.796, Tmax = 0.913k = 66
5901 measured reflectionsl = 2015
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.055Hydrogen site location: geom for CH and difmap for NH
wR(F2) = 0.124H atoms treated by a mixture of independent and constrained refinement
S = 1.14 w = 1/[σ2(Fo2) + (0.0437P)2 + 0.9103P]
where P = (Fo2 + 2Fc2)/3
2129 reflections(Δ/σ)max < 0.001
163 parametersΔρmax = 0.31 e Å3
3 restraintsΔρmin = 0.28 e Å3
Crystal data top
C6H7N4+·C2Cl3O2V = 1177.2 (2) Å3
Mr = 297.53Z = 4
Monoclinic, P21/cMo Kα radiation
a = 12.4010 (13) ŵ = 0.77 mm1
b = 5.5664 (6) ÅT = 298 K
c = 17.3648 (18) Å0.31 × 0.13 × 0.12 mm
β = 100.858 (2)°
Data collection top
Bruker APEX area-detector
diffractometer
2129 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
1812 reflections with I > 2σ(I)
Tmin = 0.796, Tmax = 0.913Rint = 0.031
5901 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0553 restraints
wR(F2) = 0.124H atoms treated by a mixture of independent and constrained refinement
S = 1.14Δρmax = 0.31 e Å3
2129 reflectionsΔρmin = 0.28 e Å3
163 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
xyzUiso*/Ueq
Cl10.71002 (8)0.82356 (16)0.70084 (6)0.0519 (3)
Cl20.52275 (7)0.67802 (19)0.58778 (6)0.0582 (3)
Cl30.58366 (9)0.41198 (19)0.73127 (6)0.0643 (3)
O10.6633 (2)0.2887 (5)0.56260 (15)0.0603 (8)
O20.8033 (2)0.3819 (5)0.65586 (18)0.0690 (9)
N10.9417 (2)0.0367 (5)0.62658 (17)0.0408 (7)
N21.0299 (2)0.2672 (6)0.58630 (16)0.0448 (7)
N30.8404 (2)0.3665 (5)0.46057 (16)0.0421 (7)
N40.7490 (2)0.0753 (6)0.49863 (16)0.0411 (7)
C11.0397 (3)0.0192 (7)0.6768 (2)0.0511 (10)
H11.06500.11640.72000.061*
C21.0926 (3)0.1663 (7)0.6515 (2)0.0539 (10)
H21.16220.21900.67510.065*
C30.9382 (3)0.1388 (6)0.57350 (18)0.0341 (7)
C40.8453 (3)0.1900 (6)0.51222 (18)0.0342 (7)
C50.6821 (3)0.1835 (7)0.4371 (2)0.0491 (10)
H50.61050.13910.41560.059*
C60.7382 (3)0.3641 (7)0.4135 (2)0.0485 (9)
H60.71270.46970.37260.058*
C70.6342 (3)0.5741 (6)0.65736 (19)0.0367 (8)
C80.7085 (3)0.3986 (6)0.62063 (19)0.0360 (8)
H1A0.894 (2)0.140 (5)0.632 (2)0.043*
H3A0.889 (2)0.469 (5)0.455 (2)0.043*
H4A0.729 (3)0.038 (5)0.5259 (18)0.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0594 (6)0.0357 (5)0.0580 (6)0.0003 (4)0.0043 (4)0.0115 (4)
Cl20.0425 (5)0.0595 (6)0.0664 (6)0.0212 (5)0.0058 (4)0.0084 (5)
Cl30.0770 (7)0.0506 (6)0.0775 (7)0.0055 (5)0.0456 (6)0.0090 (5)
O10.0639 (17)0.0609 (18)0.0489 (15)0.0302 (14)0.0077 (13)0.0206 (14)
O20.0375 (15)0.071 (2)0.092 (2)0.0179 (14)0.0051 (14)0.0387 (17)
N10.0302 (15)0.0423 (18)0.0496 (17)0.0074 (13)0.0071 (13)0.0115 (14)
N20.0359 (16)0.0509 (18)0.0461 (17)0.0130 (14)0.0043 (13)0.0074 (14)
N30.0384 (16)0.0480 (18)0.0393 (15)0.0131 (14)0.0057 (13)0.0082 (14)
N40.0393 (16)0.0452 (18)0.0380 (16)0.0130 (14)0.0055 (12)0.0092 (13)
C10.0367 (19)0.059 (2)0.053 (2)0.0033 (18)0.0018 (16)0.0180 (19)
C20.0353 (19)0.065 (3)0.056 (2)0.0135 (19)0.0055 (16)0.012 (2)
C30.0323 (17)0.0365 (18)0.0351 (17)0.0072 (14)0.0103 (13)0.0009 (14)
C40.0337 (17)0.0375 (19)0.0328 (17)0.0107 (14)0.0096 (13)0.0002 (14)
C50.040 (2)0.059 (2)0.044 (2)0.0156 (18)0.0019 (16)0.0093 (18)
C60.044 (2)0.058 (2)0.0397 (19)0.0085 (18)0.0025 (16)0.0120 (18)
C70.0377 (18)0.0309 (17)0.0409 (18)0.0060 (14)0.0056 (14)0.0013 (14)
C80.0390 (19)0.0292 (17)0.0393 (18)0.0069 (14)0.0064 (15)0.0018 (15)
Geometric parameters (Å, º) top
Cl1—C71.765 (3)N3—H3A0.843 (18)
Cl2—C71.754 (3)N4—C41.335 (4)
Cl3—C71.777 (3)N4—C51.363 (4)
O1—C81.221 (4)N4—H4A0.854 (18)
O2—C81.222 (4)C1—C21.341 (5)
N1—C31.338 (4)C1—H10.9300
N1—C11.359 (4)C2—H20.9300
N1—H1A0.845 (18)C3—C41.443 (4)
N2—C31.325 (4)C5—C61.330 (5)
N2—C21.368 (4)C5—H50.9300
N3—C41.324 (4)C6—H60.9300
N3—C61.373 (4)C7—C81.559 (4)
C3—N1—C1107.4 (3)N3—C4—N4108.1 (3)
C3—N1—H1A130 (2)N3—C4—C3125.1 (3)
C1—N1—H1A122 (2)N4—C4—C3126.8 (3)
C3—N2—C2104.7 (3)C6—C5—N4107.4 (3)
C4—N3—C6108.3 (3)C6—C5—H5126.3
C4—N3—H3A129 (2)N4—C5—H5126.3
C6—N3—H3A123 (2)C5—C6—N3107.6 (3)
C4—N4—C5108.6 (3)C5—C6—H6126.2
C4—N4—H4A127 (2)N3—C6—H6126.2
C5—N4—H4A124 (2)C8—C7—Cl2112.0 (2)
C2—C1—N1106.2 (3)C8—C7—Cl1111.1 (2)
C2—C1—H1126.9Cl2—C7—Cl1108.81 (17)
N1—C1—H1126.9C8—C7—Cl3107.1 (2)
C1—C2—N2110.5 (3)Cl2—C7—Cl3109.00 (18)
C1—C2—H2124.8Cl1—C7—Cl3108.82 (17)
N2—C2—H2124.8O1—C8—O2128.6 (3)
N2—C3—N1111.3 (3)O1—C8—C7115.9 (3)
N2—C3—C4123.9 (3)O2—C8—C7115.4 (3)
N1—C3—C4124.7 (3)
C3—N1—C1—C20.6 (4)N1—C3—C4—N3178.5 (3)
N1—C1—C2—N20.1 (5)N2—C3—C4—N4176.6 (3)
C3—N2—C2—C10.4 (5)N1—C3—C4—N40.5 (6)
C2—N2—C3—N10.7 (4)C4—N4—C5—C60.0 (4)
C2—N2—C3—C4176.7 (3)N4—C5—C6—N30.3 (5)
C1—N1—C3—N20.8 (4)C4—N3—C6—C50.5 (4)
C1—N1—C3—C4176.5 (3)Cl2—C7—C8—O126.5 (4)
C6—N3—C4—N40.4 (4)Cl1—C7—C8—O1148.4 (3)
C6—N3—C4—C3177.9 (3)Cl3—C7—C8—O192.9 (3)
C5—N4—C4—N30.3 (4)Cl2—C7—C8—O2156.5 (3)
C5—N4—C4—C3178.0 (3)Cl1—C7—C8—O234.6 (4)
N2—C3—C4—N31.4 (5)Cl3—C7—C8—O284.1 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O20.85 (2)1.85 (2)2.688 (4)172 (3)
N3—H3A···N2i0.84 (2)2.00 (2)2.811 (4)163 (3)
N4—H4A···O10.85 (2)1.79 (2)2.630 (4)167 (3)
Symmetry code: (i) x+2, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC6H7N4+·C2Cl3O2
Mr297.53
Crystal system, space groupMonoclinic, P21/c
Temperature (K)298
a, b, c (Å)12.4010 (13), 5.5664 (6), 17.3648 (18)
β (°) 100.858 (2)
V3)1177.2 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.77
Crystal size (mm)0.31 × 0.13 × 0.12
Data collection
DiffractometerBruker APEX area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2002)
Tmin, Tmax0.796, 0.913
No. of measured, independent and
observed [I > 2σ(I)] reflections
5901, 2129, 1812
Rint0.031
(sin θ/λ)max1)0.600
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.055, 0.124, 1.14
No. of reflections2129
No. of parameters163
No. of restraints3
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.31, 0.28

Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2002), SHELXL97.

Selected geometric parameters (Å, º) top
O1—C81.221 (4)N3—C61.373 (4)
O2—C81.222 (4)N4—C41.335 (4)
N1—C31.338 (4)N4—C51.363 (4)
N1—C11.359 (4)C1—C21.341 (5)
N2—C31.325 (4)C3—C41.443 (4)
N2—C21.368 (4)C5—C61.330 (5)
N3—C41.324 (4)C7—C81.559 (4)
C3—N1—C1107.4 (3)N3—C4—N4108.1 (3)
C3—N2—C2104.7 (3)N3—C4—C3125.1 (3)
C4—N3—C6108.3 (3)N4—C4—C3126.8 (3)
C4—N4—C5108.6 (3)C6—C5—N4107.4 (3)
C2—C1—N1106.2 (3)C5—C6—N3107.6 (3)
C1—C2—N2110.5 (3)O1—C8—O2128.6 (3)
N2—C3—N1111.3 (3)O1—C8—C7115.9 (3)
N2—C3—C4123.9 (3)O2—C8—C7115.4 (3)
N1—C3—C4124.7 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O20.845 (18)1.848 (19)2.688 (4)172 (3)
N3—H3A···N2i0.843 (18)2.00 (2)2.811 (4)163 (3)
N4—H4A···O10.854 (18)1.79 (2)2.630 (4)167 (3)
Symmetry code: (i) x+2, y+1, z+1.
 

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