3,3′-Diethyl-1,1′-butyl­enedi­[5(6)-methyl­benzimidazolium] diiodide dihydrate

The molecule of the title compound, C₂₄H₃₂N₄²⁺·2I⁻·2H₂O, possesses C_i symmetry with the inversion center at the mid-point of the central C—C bond between two benzimidazolium rings. In the crystal structure, the mol­ecules stack along the a axis, forming channels occupied by a chain of I⁻ ions bridged by water mol­ecules via O—H...I hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.010 Å
• R factor = 0.057
• wR factor = 0.114
• Data-to-parameter ratio = 21.5

checkCIF results

No syntax errors found



ADDSYM reports no extra symmetry

General Notes



FORMU_01  There is a discrepancy between the atom counts in the
          _chemical_formula_sum and _chemical_formula_moiety. This is
          usually due to the moiety formula being in the wrong format.
          Atom count from _chemical_formula_sum:   C24 H36 I2 N4 O2
          Atom count from _chemical_formula_moiety:C24 H32 I2 N4

---

S1. Comment

Bis-benzimidazoles constitute a family of heterocycles that have begun to attracted particular interest because of their potential use in cancer therapy by DNA binding and blocking purposes, and their use as metal ligands (Rezende et al., 2001). A previous study of bis-benzimidazoles differing in the number of cationic groups and benzimidazole subunits suggested that, although electrostatic interactions and hydrogen bonding provided some binding energy, the single most important factor for DNA binding are the van der Waals interactions within the minor groove of DNA (Cazarny et al., 1995).

In light of the general importance of benzimidazole compounds, the study of benzimidazoles and bis-benzimidazole derivatives remaines an active area of research, in spite of previous extensive investigations. Benzimidazole itself and the 5- or 6-substituted derivatives can show a tautomerism at the imidazole ring (Elderfield, 1957). Following our work on the synthesis and antibacterial activity of bis-benzimidazole compounds (Küçükbay et al., 2003), we studied the crystal structure of the title compound, (I), in order to observe whether the same tautomerism could exist in this type of bis-benzimidazole derivative.

The structure of (I) has a step-like non-planar conformation (Fig. 1), and the benzimidazolium rings are planar, within experimental error. The tautomerism at the imidazole ring is found to be present. Atom C13A is bonded to atom C3, and atom C13B to atom C4, with site occupancies of 0.45 (1) and 0.55 (1), respectively. The bond lengths and angles in (I) agree with the corresponding values in bis(1-methyl-3-ethylbenzimidazolidine-2-ylium) tetrafluoroborate (Aydın et al., 1998), in 1,3-dimethylbenzimidazole-2-selenone (Aydın et al., 1999), in 1-(2-ethoxyethyl)-3-(2-methoxyethyl)benzimidazolium chloride monohydrate (Öztürk et al., 2001), and in 3,3'-bis(3-cyanopropyl)-1,1'-propylenedi(benzimidazolium) dichloride dihydrate (Akkurt et al., 2003).

In the crystal structure, the molecules stack up the a axis, forming channels occupied by a chain of I⁻ ions bridged by water molecules via O—H···I hydrogen bonds (Fig. 2). There are also two C—H···X hydrogen bonds involving the benzimidazolium cation and the water molecule and the I⁻ anion (Table 2).

S2. Experimental

All experiments were performed under argon using freshly distilled dry solvents. ¹H-NMR and ¹³C-NMR spectra were recorded using a Bruker DPX-400 high performance digital FT-NMR (Bruker WM360, Bruker Instruments, Inc., Billercia, USA) spectrometer. Melting points were recorded using an electrothermal melting point apparatus (Electrothermal 9200, Electrothermal Engineering Ltd., Essex, UK) and are uncorrected. The starting reactant 1,1'-butylenedi[5(6)-methylbenzimidazole] was synthesized from 5(6)-methylbenzimidazole and 1,4-dibromobutane, according to a literature procedure (Küçükbay et al., 2003). 5(6)-Methylbenzimidazole shows a tautomerism at the imidazole ring, as indicated in the literature (Elderfield, 1957). Hence, the starting compound is a mixture of both 5-methyl- and 6-methylbenzimidazole. The title compound, (I), was synthesized by adding ethyl iodide (0.4 ml, 4.95 mmol) to a solution of 1,1'-butylenedi[5(6)-methylbenzimidazole] (0.78 g, 2.47 mmol) in DMF (2 ml). The mixture was refluxed for 5 h. All the volatiles were then driven off and the crude product obtained was recrystallized from EtOH/Et₂O (3:1) giving yellow crystals (yield: 1.48 g, 96%; m.p.: 506–507 K).

¹H NMR (DMSO): δ 1.57 (t, CH₂CH₃, 6H), 2.07 (s, NCH₂CH₂CH₂CH₂N, 4H), 2.55 (s, CH₃, 6H), 4.50 (q, NCH₂CH₃, 4H), 4.53 (s, NCH₂CH₂CH₂CH₂N, 4H), 7.49–8.03 (m, Ar—H, 6H), 9.77 (s, CH, 2H). ¹³C NMR (DMSO): δ 15.90, 22.93, 27.32, 47.94, 48.03, 114.84, 115.04, 129.83, 131.17, 133.10, 138.74, 143.09. Analysis calculated for C₂₄H₃₂N₄I₂: C 45.71, H 5.08, N 8.89%; found: C 45.60, H 5.02, N 8.84%.

S3. Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms. The U_iso values of the H atoms of the water molecule and the methyl groups were made equal to 1.5U_eq(parent atom).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens,1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 1990) and WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. A view of the molecular packing and the hydrogen-bond contacts of (I).

3,3'-Diethyl-1,1'-butylenedi[5(6)-methylbenzimidazolium] diiodide dihydrate

Crystal data

C24H32N41^2+·2I^−·2H2O	F(000) = 660
Mr = 666.37	Dx = 1.566 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3391 reflections
a = 5.4761 (3) Å	θ = 2.5–28.3°
b = 21.7289 (12) Å	µ = 2.25 mm^−1
c = 12.2512 (6) Å	T = 293 K
β = 104.156 (2)°	Prism, yellow
V = 1413.50 (13) Å^3	0.40 × 0.26 × 0.24 mm
Z = 2

Data collection

Siemens SMART CCD area-detector diffractometer	2496 reflections with I > 2σ(I)
Detector resolution: 8.33 pixels mm^-1	Rint = 0.017
ω scans	θmax = 28.3°, θmin = 2.5°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −7→7
Tmin = 0.442, Tmax = 0.583	k = −28→25
8590 measured reflections	l = −12→16
3391 independent reflections

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)] = 0.057	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.114	H-atom parameters constrained
S = 0.97	w = 1/[σ^2(Fo^2) + (0.0206P)^2 + 4.7667P] where P = (Fo^2 + 2Fc^2)/3
3391 reflections	(Δ/σ)max = 0.001
158 parameters	Δρmax = 0.77 e Å^−3
0 restraints	Δρmin = −0.79 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F^{2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F}2, conventional R-factors R are based on F, with F set to zero for negative F^{2. The observed criterion of F}2 > σ(F^{2) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F}2 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	0.4652 (9)	0.3146 (2)	0.3384 (4)	0.0749 (17)
N2	0.3547 (7)	0.4101 (2)	0.3490 (4)	0.0631 (16)
C1	0.5781 (10)	0.3476 (3)	0.2676 (5)	0.0754 (19)
C2	0.7337 (12)	0.3288 (3)	0.1970 (6)	0.089 (3)
C3	0.8066 (13)	0.3749 (5)	0.1367 (6)	0.099 (3)
C4	0.7370 (14)	0.4351 (4)	0.1394 (5)	0.096 (3)
C5	0.5821 (11)	0.4531 (3)	0.2086 (5)	0.086 (3)
C6	0.5050 (10)	0.4080 (3)	0.2727 (4)	0.0677 (19)
C7	0.3350 (10)	0.3538 (3)	0.3870 (5)	0.0714 (19)
C8	0.4981 (14)	0.2480 (3)	0.3612 (7)	0.107 (3)
C9	0.3313 (16)	0.2235 (3)	0.4278 (6)	0.109 (3)
C10	0.2315 (9)	0.4653 (2)	0.3830 (5)	0.0696 (17)
C11	0.3694 (9)	0.4890 (2)	0.4972 (4)	0.0629 (17)
C13B	0.839 (3)	0.4733 (10)	0.0695 (12)	0.150 (8)	0.553 (14)
C13A	0.962 (3)	0.3633 (8)	0.0514 (12)	0.095 (6)	0.447 (14)
O1W	0.4412 (11)	0.5993 (2)	0.2160 (5)	0.129 (3)
I1	0.95298 (8)	0.34521 (2)	0.61220 (4)	0.0924 (2)
H2A	0.78240	0.28810	0.19220	0.1070*
H5A	0.53240	0.49390	0.21160	0.1030*
H7A	0.24480	0.34310	0.43940	0.0860*
H8A	0.46650	0.22610	0.29010	0.1290*
H8B	0.67140	0.24030	0.40100	0.1290*
H9A	0.35140	0.17970	0.43450	0.1640*
H9B	0.15960	0.23300	0.39120	0.1640*
H9C	0.37350	0.24170	0.50140	0.1640*
H10A	0.05990	0.45510	0.38440	0.0830*
H10B	0.22480	0.49750	0.32750	0.0830*
H11A	0.27350	0.52260	0.51820	0.0760*
H11B	0.37760	0.45640	0.55210	0.0760*
H13D	0.81700	0.45450	−0.00310	0.2230*	0.553 (14)
H13E	1.01550	0.47930	0.10250	0.2230*	0.553 (14)
H13F	0.75480	0.51240	0.06140	0.2230*	0.553 (14)
H3A	0.91650	0.36570	0.08870	0.1180*	0.553 (14)
H4A	0.79080	0.46590	0.09410	0.1150*	0.447 (14)
H13A	1.07790	0.39660	0.05370	0.1430*	0.447 (14)
H13B	0.85160	0.36060	−0.02260	0.1430*	0.447 (14)
H13C	1.05320	0.32550	0.06920	0.1430*	0.447 (14)
H1W	0.34230	0.61700	0.24970	0.1940*
H2W	0.56160	0.62390	0.21570	0.1940*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.066 (3)	0.063 (3)	0.084 (3)	0.007 (2)	−0.004 (2)	−0.025 (2)
N2	0.052 (2)	0.067 (3)	0.066 (3)	0.0047 (19)	0.0062 (18)	−0.020 (2)
C1	0.059 (3)	0.088 (4)	0.070 (3)	0.001 (3)	−0.002 (3)	−0.025 (3)
C2	0.069 (4)	0.108 (5)	0.079 (4)	0.015 (3)	−0.003 (3)	−0.048 (4)
C3	0.071 (4)	0.144 (7)	0.077 (4)	−0.008 (4)	0.010 (3)	−0.028 (5)
C4	0.085 (5)	0.137 (7)	0.059 (4)	−0.017 (4)	0.003 (3)	−0.007 (4)
C5	0.067 (4)	0.112 (5)	0.068 (4)	−0.005 (3)	−0.002 (3)	−0.012 (4)
C6	0.054 (3)	0.086 (4)	0.055 (3)	0.002 (3)	−0.002 (2)	−0.022 (3)
C7	0.057 (3)	0.071 (3)	0.079 (4)	0.003 (2)	0.003 (3)	−0.021 (3)
C8	0.097 (5)	0.070 (4)	0.144 (7)	0.007 (4)	0.010 (5)	−0.024 (4)
C9	0.132 (7)	0.081 (5)	0.102 (5)	0.014 (4)	0.003 (5)	0.001 (4)
C10	0.053 (3)	0.070 (3)	0.077 (3)	0.010 (2)	−0.001 (2)	−0.018 (3)
C11	0.059 (3)	0.063 (3)	0.066 (3)	0.003 (2)	0.014 (2)	−0.013 (2)
C13B	0.108 (12)	0.26 (2)	0.082 (10)	−0.014 (13)	0.025 (8)	0.019 (12)
C13A	0.071 (9)	0.134 (14)	0.085 (10)	−0.006 (8)	0.027 (7)	−0.033 (9)
O1W	0.146 (5)	0.112 (4)	0.133 (5)	−0.015 (4)	0.041 (4)	0.006 (4)
I1	0.0797 (3)	0.0926 (3)	0.1012 (3)	−0.0053 (2)	0.0148 (2)	0.0164 (3)

Geometric parameters (Å, º)

O1W—H2W	0.8495	C3—H3A	0.9597
O1W—H1W	0.8492	C4—H4A	0.9606
N1—C7	1.340 (8)	C5—H5A	0.9307
N1—C8	1.477 (8)	C7—H7A	0.9302
N1—C1	1.382 (8)	C8—H8B	0.9695
N2—C10	1.485 (6)	C8—H8A	0.9703
N2—C6	1.389 (7)	C9—H9B	0.9600
N2—C7	1.323 (8)	C9—H9C	0.9596
C1—C6	1.378 (9)	C9—H9A	0.9593
C1—C2	1.415 (9)	C10—H10A	0.9697
C2—C3	1.361 (12)	C10—H10B	0.9701
C3—C13A	1.521 (17)	C11—H11A	0.9701
C3—C4	1.365 (14)	C11—H11B	0.9703
C4—C5	1.394 (10)	C13A—H13B	0.9606
C4—C13B	1.40 (2)	C13A—H13C	0.9583
C5—C6	1.385 (9)	C13A—H13A	0.9583
C8—C9	1.466 (11)	C13B—H13E	0.9610
C10—C11	1.509 (7)	C13B—H13F	0.9601
C11—C11^i	1.494 (7)	C13B—H13D	0.9592
C2—H2A	0.9297
I1···C7^ii	3.853 (6)	H2W···H8A^v	2.2260
I1···O1W^i	3.573 (6)	H2W···C8^v	2.8487
I1···O1W^iii	3.671 (6)	H2W···C9^v	2.9365
I1···C7	3.812 (6)	H3A···H13E	2.5240
I1···H7A^ii	2.9483	H3A···H13D	2.2327
I1···H1W^i	2.7367	H4A···H13A	2.3162
I1···H2W^iii	3.0366	H5A···O1W	2.3475
I1···H2A^iv	3.2668	H5A···C10	3.0337
I1···H11A^i	3.3722	H5A···H10B	2.4555
O1W···C8^v	3.406 (8)	H5A···H13F	2.4753
O1W···C5	3.276 (8)	H7A···C9	2.6516
O1W···I1^iii	3.671 (6)	H7A···I1^vii	2.9483
O1W···I1^i	3.573 (6)	H7A···H9B	2.4809
O1W···H8A^v	2.8055	H7A···H9C	2.3804
O1W···H5A	2.3475	H8A···C2	3.0394
O1W···H13B^vi	2.6619	H8A···H2W^viii	2.2260
O1W···H13D^vi	2.8922	H8A···O1W^viii	2.8055
N2···H11A^i	2.7038	H8B···C13A^iv	3.0921
C2···C7^ii	3.579 (9)	H8B···H13B^iv	2.4910
C4···C10^ii	3.566 (9)	H9A···C13A^ix	2.9942
C5···O1W	3.276 (8)	H9A···H2W^viii	2.3478
C6···C11^i	3.533 (7)	H9A···H13C^ix	2.5924
C7···I1^vii	3.853 (6)	H9B···H7A	2.4809
C7···C2^vii	3.579 (9)	H9B···C7	2.7999
C7···I1	3.812 (6)	H9C···C7	2.7924
C8···O1W^viii	3.406 (8)	H9C···H7A	2.3804
C9···C13A^ix	3.382 (18)	H9C···H13C^ix	2.5712
C10···C4^vii	3.566 (9)	H10A···H11A^xiii	2.4612
C11···C6^i	3.533 (7)	H10A···C5^vii	2.9547
C13A···C9^x	3.382 (18)	H10B···C5	2.8766
C13B···C13B^xi	2.97 (2)	H10B···H5A	2.4555
C2···H8A	3.0394	H10B···H11B^i	2.5197
C5···H10A^ii	2.9547	H11A···C6^i	2.9644
C5···H10B	2.8766	H11A···N2^i	2.7038
C6···H11A^i	2.9644	H11A···I1^i	3.3722
C7···H9C	2.7924	H11A···H10A^xiii	2.4612
C7···H9B	2.7999	H11B···H10B^i	2.5197
C7···H11B	2.9808	H11B···C7	2.9808
C8···H2A	3.0077	H13A···H4A	2.3162
C8···H2W^viii	2.8487	H13B···H8B^xii	2.4910
C9···H2W^viii	2.9365	H13B···O1W^vi	2.6619
C9···H7A	2.6516	H13C···C9^x	2.7828
C9···H13C^ix	2.7828	H13C···H2A	2.4946
C10···H5A	3.0337	H13C···H9A^x	2.5924
C13A···H8B^xii	3.0921	H13C···H9C^x	2.5712
C13A···H9A^x	2.9942	H13D···H3A	2.2327
C13B···H13F^xi	3.0596	H13D···O1W^vi	2.8922
C13B···H13D^xi	2.7242	H13D···C13B^xi	2.7242
C13B···H13E^xi	2.6376	H13D···H13E^xi	2.2226
H1W···I1^i	2.7367	H13E···C13B^xi	2.6376
H2A···I1^xii	3.2668	H13E···H3A	2.5240
H2A···C8	3.0077	H13E···H13D^xi	2.2226
H2A···H13C	2.4946	H13F···H5A	2.4753
H2W···H9A^v	2.3478	H13F···C13B^xi	3.0596
H2W···I1^iii	3.0366
H1W—O1W—H2W	107.76	N2—C7—H7A	125.23
C1—N1—C7	108.5 (5)	N1—C8—H8A	108.91
C7—N1—C8	126.3 (5)	N1—C8—H8B	108.87
C1—N1—C8	125.1 (5)	C9—C8—H8B	108.90
C6—N2—C7	108.6 (5)	H8A—C8—H8B	107.73
C7—N2—C10	124.5 (5)	C9—C8—H8A	108.85
C6—N2—C10	126.9 (5)	C8—C9—H9B	109.54
N1—C1—C6	106.6 (5)	C8—C9—H9C	109.50
C2—C1—C6	121.9 (6)	C8—C9—H9A	109.51
N1—C1—C2	131.5 (6)	H9A—C9—H9C	109.40
C1—C2—C3	114.8 (6)	H9B—C9—H9C	109.48
C2—C3—C4	124.8 (7)	H9A—C9—H9B	109.40
C4—C3—C13A	112.4 (9)	N2—C10—H10B	109.14
C2—C3—C13A	122.6 (10)	C11—C10—H10A	109.21
C3—C4—C5	119.9 (7)	C11—C10—H10B	109.17
C5—C4—C13B	126.7 (11)	H10A—C10—H10B	107.85
C3—C4—C13B	113.4 (10)	N2—C10—H10A	109.21
C4—C5—C6	117.5 (6)	C10—C11—H11A	108.79
N2—C6—C1	106.8 (5)	C10—C11—H11B	108.75
C1—C6—C5	121.1 (5)	C11^i—C11—H11A	108.75
N2—C6—C5	132.2 (6)	C11^i—C11—H11B	108.68
N1—C7—N2	109.5 (5)	H11A—C11—H11B	107.57
N1—C8—C9	113.4 (6)	C3—C13A—H13B	109.25
N2—C10—C11	112.2 (4)	C3—C13A—H13C	109.49
C10—C11—C11^i	114.1 (4)	H13A—C13A—H13C	109.63
C1—C2—H2A	122.57	H13B—C13A—H13C	109.58
C3—C2—H2A	122.61	H13A—C13A—H13B	109.47
C4—C3—H3A	115.79	C3—C13A—H13A	109.41
C2—C3—H3A	119.36	C4—C13B—H13D	109.61
C3—C4—H4A	121.78	C4—C13B—H13E	109.46
C5—C4—H4A	118.30	C4—C13B—H13F	109.50
C6—C5—H5A	121.27	H13D—C13B—H13E	109.46
C4—C5—H5A	121.24	H13D—C13B—H13F	109.44
N1—C7—H7A	125.29	H13E—C13B—H13F	109.37
C7—N1—C1—C2	−179.8 (7)	C2—C1—C6—N2	179.8 (5)
C7—N1—C1—C6	−1.8 (6)	C2—C1—C6—C5	−0.2 (9)
C8—N1—C1—C2	3.8 (10)	N1—C1—C6—N2	1.5 (6)
C8—N1—C1—C6	−178.2 (6)	N1—C1—C2—C3	178.6 (6)
C1—N1—C7—N2	1.3 (7)	C6—C1—C2—C3	0.8 (9)
C8—N1—C7—N2	177.6 (6)	N1—C1—C6—C5	−178.4 (5)
C1—N1—C8—C9	−172.5 (6)	C1—C2—C3—C4	−1.1 (11)
C7—N1—C8—C9	11.8 (10)	C2—C3—C4—C5	0.7 (11)
C7—N2—C6—C1	−0.8 (6)	C2—C3—C4—C13B	179.8 (9)
C7—N2—C6—C5	179.2 (6)	C3—C4—C5—C6	0.1 (10)
C10—N2—C6—C1	179.9 (5)	C13B—C4—C5—C6	−178.9 (10)
C10—N2—C6—C5	−0.1 (9)	C4—C5—C6—N2	179.7 (6)
C6—N2—C7—N1	−0.3 (6)	C4—C5—C6—C1	−0.3 (9)
C10—N2—C7—N1	179.0 (5)	N2—C10—C11—C11^i	63.4 (5)
C6—N2—C10—C11	−102.8 (6)	C10—C11—C11^i—C10^i	180.0 (4)
C7—N2—C10—C11	78.0 (6)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x+1, y, z; (iii) −x+2, −y+1, −z+1; (iv) x, −y+1/2, z+1/2; (v) −x+1, y+1/2, −z+1/2; (vi) −x+1, −y+1, −z; (vii) x−1, y, z; (viii) −x+1, y−1/2, −z+1/2; (ix) x−1, −y+1/2, z+1/2; (x) x+1, −y+1/2, z−1/2; (xi) −x+2, −y+1, −z; (xii) x, −y+1/2, z−1/2; (xiii) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W···I1^i	0.85	2.74	3.573 (6)	169
O1W—H2W···I1^iii	0.85	3.04	3.671 (6)	133
C5—H5A···O1W	0.93	2.35	3.276 (8)	175
C7—H7A···I1^vii	0.93	2.95	3.853 (6)	165

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