3,3′-[1,2-Phenyl­enebis(methyl­ene)]bis­(1-ethyl-1H-benzimidazol-1-ium) bis­(hexa­flourophosphate)

Rosenani A Haque; Muhammad Adnan Iqbal; Mohd Mustaqim Rosli; Hoong-Kun Fun

doi:10.1107/S1600536812019344

. 2012 May 5;68(Pt 6):o1635. doi: 10.1107/S1600536812019344

3,3′-[1,2-Phenylenebis(methylene)]bis(1-ethyl-1H-benzimidazol-1-ium) bis(hexaflourophosphate)

Rosenani A Haque ^a, Muhammad Adnan Iqbal ^a, Mohd Mustaqim Rosli ^b, Hoong-Kun Fun ^b,^*,^‡

PMCID: PMC3379238 PMID: 22719436

Abstract

In the title compound, C₂₆H₂₈N₄ ²⁺·2PF₆ ⁻, the complete cation is generated by a crystallographic twofold axis. The benzimidazole ring is almost planar (r.m.s. deviation = 0.0207 Å) and makes dihedral angles of 50.12 (2)° with its symmetry-related component and 65.81 (2)° with the central benzene ring. In the crystal, molecules are linked into a three-dimensional network by C—H⋯F interactions. A π–π interaction with a centroid–centroid distance of 3.530 (1) Å is observed. Four F atoms of the hexafluorophosphate anion are disordered over two sets of sites in a 0.889 (6):0.111 (6) ratio.

Related literature

For the biological applications of benzimidazoles, see: Narasimhan et al. (2012 ▶). For a related structure, see: Haque et al. (2012 ▶). graphic file with name e-68-o1635-scheme1.jpg

Experimental

Crystal data

C₂₆H₂₈N₄ ²⁺·2PF₆ ⁻
M _r = 686.46
Monoclinic,
a = 23.2016 (5) Å
b = 8.1526 (2) Å
c = 16.9992 (4) Å
β = 121.274 (1)°
V = 2748.23 (11) Å³
Z = 4
Mo Kα radiation
μ = 0.27 mm⁻¹
T = 100 K
0.26 × 0.26 × 0.14 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.933, T _max = 0.963
14787 measured reflections
3921 independent reflections
3156 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.098
S = 1.05
3921 reflections
217 parameters
H-atom parameters constrained
Δρ_max = 0.48 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812019344/hb6760sup1.cif

e-68-o1635-sup1.cif^{(24.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812019344/hb6760Isup2.hkl

e-68-o1635-Isup2.hkl^{(192.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯F6ⁱ	0.95	2.42	3.142 (3)	133
C3—H3A⋯F5ⁱⁱ	0.95	2.45	3.374 (2)	166
C5—H5A⋯F5ⁱⁱⁱ	0.95	2.52	3.420 (3)	159
C6—H6A⋯F4^iv	0.95	2.53	3.392 (2)	151
C8—H8B⋯F1ⁱ	0.99	2.39	3.350 (3)	164
C13—H13C⋯F1^v	0.98	2.55	3.523 (2)	174
C13—H13C⋯F5^v	0.98	2.50	3.166 (2)	125

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

RAH thanks Universiti Sains Malaysia (USM) for the Research University (RU) grants (1001/PKIMIA/811157 and 304/PKIMIA/6511123). MAI is grateful to (IPS) USM for financial support [fellowship: USM·IPS/JWT/1/19 (JLD 6)] and the research attachment fund [P-KM0018/10(R) − 308/AIPS/415401]. HKF thanks USM for the Research University Grant No. 1001/PFIZIK/811160.

supplementary crystallographic information

Comment

Benzimidazole-constituted compounds are known as bioactive heterocyclic compounds that are of wide interest for biological and clinical applications (Narasimhan et al., 2012). As a part of our ongoing studies in this area (Haque et al., 2012), we now describe the title compound.

All parameters in the title compound (Fig. 1) are within normal ranges. The complete molecule is generated by a crystallographic two-fold axis. The benzimidazole (N1—N2/C1—C7) ring is planar with the r.m.s 0.0207 Å. It makes a dihedral angle of 50.12 (2)° with its symmetrical component and 65.81 (2) Å with the central benzene ring (C9—C11/C9A—C11A). Four fluorine atoms (F1—F4) of the hexafluorophosphate cation are disordered over two positions with the final refined occupancies of 0.889 (6):0.111 (6).

In the crystal structure, (Fig. 2), the molecules are linked into a three-dimensional network through intermolecular C—H···F hydrogen bonds (Table 1). A π-π interaction with centroid-centroid distance of 3.530 (1) Å is observed (Cg1 = C2—C7).

Experimental

A mixture of benzimidazole (1.18 g, 10 mmol) and potassium hydroxide (1.18 g, 15 mmol) in 30 ml of DMSO was stirred at room temperature (27–28°C) for 30 min. Ethyl bromide (0.75 ml, 10 mmol) was added drop-wise into this consistently stirring mixture and it was further stirred for 2 h at same temperature, then poured into water (150 ml) and was extracted by chloroform (3 × 20 ml). The extract was filtered by five plies of filter papers with medium porosity to collect a crystal-clear solution which was evaporated under vacuum to get N-ethylbenzimidazole (I) as a thick yellowish fluid. Then, a mixture of I (0.73 g, 5 mmol) and 1,2- bis(bromomethyl)benzene (0.66 g, 2.5 mmol) in 1,4-dioxane (20 ml) was refluxed at 110°C for 12 h. The bromide salt of title compound appeared as beige-colored precipitates in a dark brown solution. The mixture was filtered and the precipitates were washed by fresh 1,4-dioxane (3 x 5 ml) and dried at room temperature for 24 h. The soft lumps so obtained were dissolved in methanol (30 ml) along with KPF₆ (1.84 g, 10 mmol) and stirred for 3 h at room temperature. The white solid that appeared was filtered, washed by fresh methanol followed by water. The compound was dried at room temperature (1.53 g, 89.5%). A saturated solution of 2.2PF₆ dissolved in acetonitrile (1 ml) was prepared. The compound was dissolved in it and the solution was evaporated at room temperature to collect colourless blocks of the title compound.