2,2′-(Iminodimethylene)bis(1H-benzimidazolium)(1+) chloride

The title compound, C₁₆H₁₆N₅⁺·Cl⁻ (nbbH⁺·Cl⁻), displays N—H...N, N—H...Cl and π–π inter­actions in the crystal packing. The Cl⁻ anion is chelated by the nbbH⁺ cation via two N—H...Cl hydrogen bonds. Inter-ion N—H...N and N—H...Cl hydrogen bonds link ions related by 2₁ screw axes into chains along the c axis. These chains are further linked by glide-plane operations to generate a three-dimensional network, which is additionally stabilized by inter­chain π–π inter­actions.

S1. Comment

Bis(benzimidazol-2-ylmethyl)amine (nbb) has been utilized extensively to synthesize various transition metal complexes (Wahnon et al., 1994; Berends & Stephan, 1984). Each benzimidazol arm of nbb possesses one imine N atom and one amine NH group. The two imine N atoms can act as coordination donors to chelate a metal ion, while the two amine NH groups are potential hydrogen-bond donors. Without metal coordination, the two imine N atoms can also behave as hydrogen-bond acceptors. Therefore, nbb is a good candidate for formation of hydrogen-bonded adducts via intermolecular interactions. We have been interested in assembly of supramolecular aggregates with benzimidazole-related compounds (Su et al., 1998, 2000; Zhang, et al., 2005) and report here the structure of the title compound, nbbH⁺·Cl⁻, (I). The single-crystal structure of nbb has been reported previously at room temperature (Calderazzo et al., 2003) and at 150 K (Tarazon Navarro & McKee, 2003); in both reports, the nbb molecule is disordered about an inversion centre

Our analysis establishes that the title compound has partial protonation of the two imine N atoms, as shown in Fig. 1. The nbbH⁺ cation adopts an almost planar conformation, the two benzimidazole rings forming a dihedral angle of 5.36 (9)°. Occupancy refinement showed that the H atom involved in ring protonation is equally disordered over the N2 and N3 sites, and each five-membered ring possesses a half-positive-charge, giving rise to the overrall nbbH⁺ cation (see scheme). The dimensions of the five-membered rings are fully consistent with this assignment. As listed in Table 1, the geometry of each benzimidazole ring is the same; in particular, the N2—C2 bond distance is identical to the N3—C10 distance [mean 1.315 (3) Å], while the N1—C2 and N4—C10 distances are also not significantly different [mean 1.335 (3) Å]. These findings are consistent with the N2—C2 and N3—C10 bonds possessing more double-bond character than the N1—C2 and N3—C10 bonds. In the disordered non-protonated nbb parent molecule at low temperature, the N═C distance is 1.3183 (17) Å and the C—N(H) distance is 1.3573 (17) Å (Tarazon Navarro & McKee, 2003).

All five N atoms of the nbbH⁺ ion are involved in hydrogen bonds, as shown in Table 2. The Cl⁻ anion is chelated by atoms N1 and N4 via N—H···Cl hydrogen bonds. Atoms N2 and N3 form mutual inter-ion N2—H···N3 and N3—H···N2 hydrogen bonds, as shown in Fig. 2, each H atom having an occupancy of 0.5. Since the nbbH⁺ cation is bent, with two methylene (CH₂) groups protruding between the two planar benzimidazole rings, the ions are not assembled into a dimer by formation of two complementary N—H···N hydrogen bonds. Instead, groups related by a 2₁ screw axis are connected in a head-to-tail fashion into an undulating one-dimensional chain, which extends along the c axis (Fig. 2). The N5/H5 moiety is also involved in a further N5—H5···Cl hydrogen bond (weaker compared with those of the chelating N—H···Cl hydrogen bonds), which links ions related by an a glide into columnar one-dimensional chains extending along the a axis, as shown in Fig. 3. This chain can also be considered to consist of oppositely overlapped nbbH⁺ cations. These cations are stacked along the a direction with overlap between five- and six-membered rings in the sequence (−1/2 + x, 3/2 − y, z), (x, y, z), (1/2 + x, 3/2 − y, z), (1 + x, y, z) etc. There exist π–π interactions between neighbouring cations. The shortest centroid-to-centroid distance is 3.554 (2) Å. The N—H···Cl hydrogen-bonded chain along the a axis is thus further stabilized by π–π stacking interactions. These chains along the a and c axial directions are also linked by N—H···N hydrogen bonds by operation of the space group n glide to generate a three-dimensional network. Thus, the crystal packing is ordered via synergetic contributions from N—H···N and N—H···Cl hydrogen bonds and π–π interactions, which together assemble the cations and anions into a three-dimensional framework.

S2. Experimental

The title compound was prepared by the condensation of iminodiacetic acid and 1,2-diaminobenzene in a 4 N HCl solution (yield 76%). Single crystals suitable for X-ray analysis were obtained by slow evaporation from ethanol solution at room temperature.

S3. Refinement

The systematic absences allow the space group to be either Pnma or Pna2₁, but a sensible solution and refinement were only possible with Pna2₁. All H atoms were located in a difference Fourier map. It was obvious from the difference maps that protonation had occurred equally at atoms N2 and N3, and the H atoms at these sites were assigned an occupancy of 0.5. Atom H5 (at N5) was clearly located such that N5 has pyramidal geometry. All H atoms were then allowed for as riding atoms (C—H = 0.93 and 0.97 Å, and N—H = 0.86 and 0.90 Å) with U_iso(H) values of 1.2 times U_eq(C,N). Friedel pairs were measured; however, the Flack (1983) parameter was indeterminate, indicating probable inversion twinning.

Computing details

Data collection: SMART (Siemens, 1993); cell refinement: SAINT (Siemens, 1995); 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, 1997); software used to prepare material for publication: PLATON (Spek, 2003).

Figures

	Fig. 1. A view of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are represented by circles of arbitrary size. Dashed lines indicate hydrogen bonds.
	Fig. 2. A view showing hydrogen-bonded chains along the c axis. Dashed lines indicate hydrogen bonds, and C-bound H atoms have been omitted. Symmetry operators are as in Table 2.
	Fig. 3. A view showing the hydrogen-bonded chain extending along the a axis. See Table 2 for details of the symmetry operator. Dashed lines indicate hydrogen bonds, and C-bound H atoms have been omitted. This plot also shows the π–π stacking between five- and six-membered rings in the sequence (bottom to top) (−1/2 + x, 3/2 − y, z), (x, y, z), (1/2 + x, 3/2 − y, z), (1 + x, y, z).

Bis(1H-benzimidazol-2-ylmethyl)aminium chloride

Crystal data

C16H16N5^+·Cl^−	F(000) = 656
Mr = 313.79	Dx = 1.384 Mg m^−3
Orthorhombic, Pna21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 1785 reflections
a = 7.607 (2) Å	θ = 2.1–24.6°
b = 13.615 (3) Å	µ = 0.26 mm^−1
c = 14.544 (3) Å	T = 293 K
V = 1506.3 (6) Å^3	Block, colorless
Z = 4	0.19 × 0.04 × 0.03 mm

Data collection

Bruker SMART 1K CCD diffractometer	2020 independent reflections
Radiation source: fine-focus sealed tube	1771 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
ϕ and ω scans	θmax = 25.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Siemens, 1996)	h = −8→9
Tmin = 0.757, Tmax = 1.000	k = −14→16
6569 measured reflections	l = −8→17

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)] = 0.027	H-atom parameters constrained
wR(F^2) = 0.067	w = 1/[σ^2(Fo^2) + (0.0419P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max = 0.001
2020 reflections	Δρmax = 0.19 e Å^−3
200 parameters	Δρmin = −0.16 e Å^−3
1 restraint	Absolute structure: Flack (1983), 637 Friedel pairs?
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.36 (7)

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	Occ. (<1)
N1	−0.0512 (2)	0.74555 (12)	0.66884 (14)	0.0374 (4)
H1	−0.0009	0.7723	0.7155	0.045*
N2	−0.1621 (2)	0.63180 (12)	0.57910 (13)	0.0361 (4)
H2	−0.1942	0.5752	0.5589	0.043*	0.50
N3	0.2418 (2)	0.55635 (13)	1.02709 (13)	0.0371 (4)
H3	0.2397	0.4944	1.0385	0.044*	0.50
N4	0.2066 (2)	0.69743 (13)	0.95583 (14)	0.0385 (5)
H4	0.1787	0.7387	0.9135	0.046*
N5	0.0272 (3)	0.61128 (13)	0.80927 (14)	0.0501 (6)
H5	−0.0758	0.6242	0.8371	0.060*
C1	−0.0079 (3)	0.57179 (15)	0.71900 (15)	0.0393 (5)
H1A	−0.0932	0.5191	0.7239	0.047*
H1B	0.0995	0.5446	0.6936	0.047*
C2	−0.0771 (3)	0.64963 (15)	0.65605 (16)	0.0349 (5)
C3	−0.1904 (3)	0.72231 (16)	0.53660 (16)	0.0346 (5)
C4	−0.2672 (3)	0.74615 (19)	0.45354 (17)	0.0444 (6)
H4A	−0.3166	0.6984	0.4159	0.053*
C5	−0.2673 (3)	0.8434 (2)	0.4290 (2)	0.0549 (7)
H5A	−0.3177	0.8618	0.3733	0.066*
C6	−0.1941 (4)	0.9153 (2)	0.4851 (2)	0.0562 (8)
H6	−0.1951	0.9803	0.4654	0.067*
C7	−0.1206 (3)	0.89294 (16)	0.5687 (2)	0.0469 (6)
H7	−0.0737	0.9412	0.6067	0.056*
C8	−0.1198 (3)	0.79431 (14)	0.59359 (17)	0.0351 (5)
C9	0.1284 (3)	0.54739 (17)	0.86727 (18)	0.0437 (6)
H9A	0.2292	0.5230	0.8334	0.052*
H9B	0.0571	0.4915	0.8851	0.052*
C10	0.1896 (3)	0.59992 (15)	0.95112 (17)	0.0364 (5)
C11	0.3012 (3)	0.63025 (15)	1.08526 (17)	0.0361 (5)
C12	0.3706 (3)	0.62602 (17)	1.17369 (18)	0.0448 (6)
H12	0.3865	0.5664	1.2038	0.054*
C13	0.4146 (3)	0.71369 (19)	1.21459 (19)	0.0505 (7)
H13	0.4630	0.7134	1.2733	0.061*
C14	0.3881 (3)	0.80322 (19)	1.1696 (2)	0.0549 (7)
H14	0.4187	0.8611	1.1995	0.066*
C15	0.3187 (3)	0.80842 (17)	1.0828 (2)	0.0479 (6)
H15	0.3004	0.8682	1.0534	0.058*
C16	0.2773 (3)	0.72020 (16)	1.04122 (17)	0.0387 (5)
Cl1	0.09411 (8)	0.88137 (4)	0.82646 (5)	0.04764 (17)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0437 (11)	0.0317 (9)	0.0369 (11)	−0.0029 (8)	−0.0012 (9)	−0.0032 (9)
N2	0.0440 (11)	0.0311 (9)	0.0332 (11)	−0.0004 (7)	0.0020 (9)	−0.0010 (9)
N3	0.0464 (11)	0.0297 (9)	0.0351 (11)	−0.0028 (8)	−0.0018 (9)	0.0023 (9)
N4	0.0447 (11)	0.0339 (10)	0.0368 (12)	−0.0003 (8)	0.0014 (10)	0.0077 (9)
N5	0.0635 (13)	0.0457 (11)	0.0410 (14)	0.0082 (9)	−0.0083 (11)	−0.0036 (10)
C1	0.0512 (14)	0.0330 (11)	0.0337 (13)	0.0025 (11)	−0.0030 (11)	−0.0003 (10)
C2	0.0382 (12)	0.0331 (11)	0.0334 (13)	−0.0009 (9)	0.0030 (11)	−0.0020 (10)
C3	0.0360 (12)	0.0339 (11)	0.0340 (13)	0.0005 (9)	0.0057 (11)	0.0030 (10)
C4	0.0468 (14)	0.0514 (14)	0.0350 (14)	0.0055 (11)	−0.0009 (12)	0.0035 (12)
C5	0.0610 (16)	0.0626 (17)	0.0409 (14)	0.0171 (13)	0.0032 (13)	0.0131 (15)
C6	0.0682 (19)	0.0403 (14)	0.0602 (19)	0.0114 (13)	0.0172 (15)	0.0177 (13)
C7	0.0489 (15)	0.0341 (12)	0.0577 (18)	−0.0002 (10)	0.0111 (13)	0.0021 (12)
C8	0.0367 (12)	0.0327 (11)	0.0360 (13)	0.0014 (9)	0.0061 (10)	0.0045 (10)
C9	0.0543 (14)	0.0380 (12)	0.0387 (13)	−0.0003 (11)	−0.0059 (11)	0.0038 (11)
C10	0.0391 (12)	0.0323 (12)	0.0380 (14)	−0.0007 (10)	0.0025 (11)	0.0036 (11)
C11	0.0358 (13)	0.0343 (12)	0.0380 (13)	0.0008 (9)	0.0030 (11)	0.0028 (11)
C12	0.0450 (14)	0.0478 (14)	0.0414 (15)	−0.0006 (11)	−0.0043 (12)	0.0033 (12)
C13	0.0506 (15)	0.0619 (17)	0.0391 (14)	−0.0081 (13)	−0.0011 (12)	−0.0073 (13)
C14	0.0578 (17)	0.0493 (15)	0.0575 (19)	−0.0147 (13)	0.0063 (14)	−0.0120 (14)
C15	0.0557 (16)	0.0345 (13)	0.0536 (17)	−0.0052 (10)	0.0076 (13)	0.0008 (13)
C16	0.0377 (12)	0.0380 (12)	0.0405 (14)	−0.0029 (10)	0.0041 (11)	0.0008 (11)
Cl1	0.0574 (3)	0.0379 (3)	0.0476 (3)	−0.0062 (2)	−0.0003 (3)	−0.0040 (3)

Geometric parameters (Å, º)

N1—C2	1.334 (3)	C4—H4A	0.93
N1—C8	1.382 (3)	C5—C6	1.390 (4)
N1—H1	0.86	C5—H5A	0.93
N2—C2	1.315 (3)	C6—C7	1.373 (4)
N2—C3	1.395 (3)	C6—H6	0.93
N2—H2	0.86	C7—C8	1.391 (3)
N3—C10	1.315 (3)	C7—H7	0.93
N3—C11	1.390 (3)	C9—C10	1.489 (3)
N3—H3	0.86	C9—H9A	0.97
N4—C10	1.336 (3)	C9—H9B	0.97
N4—C16	1.388 (3)	C11—C12	1.391 (3)
N4—H4	0.86	C11—C16	1.394 (3)
N5—C9	1.436 (3)	C12—C13	1.375 (3)
N5—C1	1.444 (3)	C12—H12	0.93
N5—H5	0.90	C13—C14	1.398 (4)
C1—C2	1.496 (3)	C13—H13	0.93
C1—H1A	0.97	C14—C15	1.370 (4)
C1—H1B	0.97	C14—H14	0.93
C3—C4	1.381 (3)	C15—C16	1.381 (3)
C3—C8	1.392 (3)	C15—H15	0.93
C4—C5	1.372 (4)
C2—N1—C8	107.71 (19)	C5—C6—H6	119.1
C2—N1—H1	126.1	C6—C7—C8	116.5 (2)
C8—N1—H1	126.1	C6—C7—H7	121.7
C2—N2—C3	106.84 (18)	C8—C7—H7	121.7
C2—N2—H2	126.6	N1—C8—C7	132.2 (2)
C3—N2—H2	126.6	N1—C8—C3	106.20 (17)
C10—N3—C11	106.43 (18)	C7—C8—C3	121.6 (2)
C10—N3—H3	126.8	N5—C9—C10	110.98 (18)
C11—N3—H3	126.8	N5—C9—H9A	109.4
C10—N4—C16	107.78 (19)	C10—C9—H9A	109.4
C10—N4—H4	126.1	N5—C9—H9B	109.4
C16—N4—H4	126.1	C10—C9—H9B	109.4
C9—N5—C1	114.08 (18)	H9A—C9—H9B	108.0
C9—N5—H5	108.7	N3—C10—N4	112.1 (2)
C1—N5—H5	108.7	N3—C10—C9	124.46 (19)
N5—C1—C2	110.96 (17)	N4—C10—C9	123.4 (2)
N5—C1—H1A	109.4	N3—C11—C12	131.0 (2)
C2—C1—H1A	109.4	N3—C11—C16	108.3 (2)
N5—C1—H1B	109.4	C12—C11—C16	120.7 (2)
C2—C1—H1B	109.4	C13—C12—C11	117.2 (2)
H1A—C1—H1B	108.0	C13—C12—H12	121.4
N2—C2—N1	111.83 (19)	C11—C12—H12	121.4
N2—C2—C1	124.26 (19)	C12—C13—C14	121.3 (3)
N1—C2—C1	123.8 (2)	C12—C13—H13	119.4
C4—C3—C8	121.3 (2)	C14—C13—H13	119.4
C4—C3—N2	131.3 (2)	C15—C14—C13	122.1 (3)
C8—C3—N2	107.4 (2)	C15—C14—H14	118.9
C5—C4—C3	117.1 (2)	C13—C14—H14	118.9
C5—C4—H4A	121.5	C14—C15—C16	116.5 (2)
C3—C4—H4A	121.5	C14—C15—H15	121.7
C4—C5—C6	121.8 (3)	C16—C15—H15	121.7
C4—C5—H5A	119.1	C15—C16—N4	132.4 (2)
C6—C5—H5A	119.1	C15—C16—C11	122.2 (2)
C7—C6—C5	121.8 (2)	N4—C16—C11	105.38 (19)
C7—C6—H6	119.1

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl1	0.86	2.31	3.146 (2)	164
N2—H2···N3^i	0.86	1.89	2.739 (2)	172
N3—H3···N2^ii	0.86	1.91	2.739 (2)	161
N4—H4···Cl1	0.86	2.41	3.247 (2)	166
N5—H5···Cl1^iii	0.90	2.52	3.306 (3)	147

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