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ISSN: 2414-3146

3-(2-Hy­dr­oxy­eth­yl)-1-(4-nitro­phen­yl)-1H-benzo[d]imidazol-3-ium bromide

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aDepartment of Chemistry, Durban University of Technology, PO Box 1334, Durban, 4000, South Africa, and bSchool of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa
*Correspondence e-mail: zamisas@ukzn.ac.za

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 29 November 2024; accepted 2 December 2024; online 10 December 2024)

The cation of the title salt, C15H14N3O3+·Br, has a dihedral angle of 24.26 (6)° between its fused imidazole and 4-nitro­phenyl rings and the N—C—C—O torsion angle associated with the hy­droxy­ethyl substituent is 60.15 (17)°. In the crystal, the bromide ions act as double acceptors for hydrogen bonds from a hydroxyl group (O—H⋯Br) and a fused imidazolium moiety (C—H⋯Br). Additionally, C—H⋯O hydrogen bonds between the phenyl group and hydroxyl oxygen atom create a two-dimensional supra­molecular network extending diagonally in the crystallographic bc plane.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

The title compound is a benzimidazolyl­idene precursor based on the 1-(4-nitro­phen­yl)benzimidazol-3-yl scaffold (Lee et al., 2004[Lee, H. M., Lu, C. Y., Chen, C. Y., Chen, W. L., Lin, H. C., Chiu, P. L. & Cheng, P. Y. (2004). Tetrahedron, 60, 5807-5825.]; Ibrahim et al., 2022[Ibrahim, H., Zamisa, S. J., Bala, M. D. & Friedrich, H. B. (2022). Z. Kristallogr. New Cryst. Struct. 237, 23-25.]) and quaternized to form a 2-hy­droxy­ethyl benzimidazolium bromide salt. Various works have reported the chemodosimetric potential of compounds with a fused 1H-benzo[d] backbone (Kumar et al., 2013[Kumar, S., Singh, P., Hundal, G., Singh Hundal, M. & Kumar, S. (2013). Chem. Commun. 49, 2667-2669.], 2015[Kumar, R., Sandhu, S., Hundal, G., Singh, P., Walia, A., Vanita, V. & Kumar, S. (2015). Org. Biomol. Chem. 13, 11129-11139.]). The bulkiness of the backbone and the steric size of the ‘wingtip’ substituents influence the properties of such compounds in the absorption of nucleophiles such as cyanide ions. Their varied structures have led to investigations into their potential medicinal uses, thereby uncovering properties such as anti­microbial and anti­cancer activities (Kadafour et al., 2022[Kadafour, A. N. W., Ibrahim, H. & Bala, M. D. (2022). J. Mol. Struct. 1262, 132997-13300.]; Ott, 2017[Ott, I. (2017). Medicinal Chemistry of Metal N-Heterocyclic Carbene (NHC) Complexes. In Inorganic and Organometallic Transition Metal Complexes with Biological Molecules and Living Cells, edited by K. K.-W. Lo, pp. 147-179. New York: Academic Press.]). Recently, we have focused on the development of imine-functionalized benzimidazolyl­idene compounds as potential ligands for earth-abundant metals that were utilized as homogeneous catalysts for the transfer hydrogenation of ketones (Abubakar & Bala, 2020[Abubakar, S. & Bala, M. D. (2020). ACS Omega, 5, 2670-2679.]; Kadafour & Bala, 2021[Kadafour, A. N. W. & Bala, M. D. (2021). J. Coord. Chem. 74, 2886-2897.]). As part of our ongoing work aimed at developing new derivatives with enhanced catalytic properties, we synthesized the title compound, C15H14N3O3+ · Br (I), and determined its crystal structure.

The asymmetric unit of (I) consists of a cationic benzoimidazolium species and a bromide ion as depicted in Fig. 1[link]. In comparison with the recently reported 3-(2-hy­droxy­eth­yl)-1-(4-nitro­phen­yl)-1H-imidazol-3-ium bromide (II) (Ibrahim et al., 2024[Ibrahim, H., Zamisa, S. J., Bala, M. D., Ntola, P. & Friedrich, H. B. (2024). IUCrData, 9, x241138.]), the presence of the benzo­imidazole moiety in (I) seem to widen the dihedral angle between the imidazole and 4-nitro­phenyl rings from 8.99 (14)° in (II) to 24.26 (5)° in (I) while causing the ethanolyl side chain to adopt a synclinal conformation with respect to the fused imidazole ring [C7—N3—C14—C15 torsion angle = 59.7 (2)°]. In the extended structure of (I), the bromide ion acts as a double acceptor for O3—H3A⋯Br1 and C7—H7⋯Br1 links (Table 1[link]) and inversion symmetry generates tetra­mers (two cations and two anions) with an R42(16) graph-set descriptor, as shown in Fig. 2[link]. Inter­molecular C—H⋯O hydrogen bonds exist between atom H13 of the phenyl moiety and O3 of the hy­droxy group (Fig. 2[link]), which link the hydrogen-bonded 16-membered rings to form a two-dimensional supra­molecular structure that extends diagonally with respect to the crystallographic bc plane (Fig. 3[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O3—H3A⋯Br1 0.84 (1) 2.39 (1) 3.2316 (11) 175
C7—H7⋯Br1i 0.95 2.68 3.5881 (16) 161
C13—H13⋯O3ii 0.95 2.39 3.3052 (19) 161
Symmetry codes: (i) [-x+1, -y, -z+1]; (ii) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}].
[Figure 1]
Figure 1
The mol­ecular structure of (I) showing displacement ellipsoids drawn at the 50% probability level.
[Figure 2]
Figure 2
Representation of C7—H7⋯Br1, O3—H3A⋯Br1 and C13—H13⋯O3 hydrogen bonds (dotted bonds) in the packing of (I).
[Figure 3]
Figure 3
Representation of the propagation of the two-dimensional supra­molecular structure in (I).

Synthesis and crystallization

The title compound was synthesized using a modified literature protocol (Ibrahim & Bala, 2016[Ibrahim, H. & Bala, M. D. (2016). New J. Chem. 40, 6986-6997.]). To a Schlenk tube initially charged with N-para nitro­phenyl benzimidazole (0.50 g, 0.0021 mol) and an excess of 2-bromo­ethanol (0.78 g, 0.0063 mol) was added dry aceto­nitrile (20 ml). The mixture was stirred and refluxed under nitro­gen for 16 h. Removal of all volatiles from the greenish grey mixture and subsequent washing with batches of dry ethyl acetate (30 ml × 5) until the washing became colourless gave a grey solid, which was shown to be pure with TLC. The grey precipitate was then dried under vacuum to yield a greyish solid of the title compound. Colourless, block-shaped crystals of (I) suitable for crystal-structure determination were grown by the slow diffusion of diethyl ether into a methano­lic solution of the title compound. Yield: 0.42 g, 55.3%. m.p. 226–228°C. 1H NMR (400 MHz, DMSO-d6): δp.p.m. 10.39 [s, 1H, NC(H)N], 8.67 (d, J = 8.9 Hz, 2 × 1H, CHp), 8.31 (d, J = 7.5 Hz, 1H, CHb), 8.21 (d, J = 8.9 Hz, 2 × 1H, CHp), 8.02 (d, J = 8.6 Hz, 1H, CHb), 7.87 (m, 2 × 1H, CHb), 5.29 (s, b, 1H, OHe), 4.74 (t, J = 9.8 Hz, 2H, CH2 e), 3.99 (t, J = 9.8 Hz, 2H, CH2 e): b = benzoyl, p = phenyl, e = ethanoyl. 13C NMR (100 MHz, DMSO-d6): δp.p.m. 148.1 (NCN), 143.2, 138.1, 131.5, 130.7, 127.6, 127.1, 126.6, 114.5, 113.4, 58.6 (CH2), 50.1 (CH2). FTIR (cm−1): νO—H 3244; νaryl C—H 3081, νalkyl C—H 2997; νC=N 1566; νNitro 1512, 1328; νC—O 1255;. LCMS (ESI+): m/z (%) 284.0635 (100) [(M—Br)]+.

Refinement

Crystallographic data and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C15H14N3O3+·Br
Mr 364.20
Crystal system, space group Monoclinic, P21/n
Temperature (K) 100
a, b, c (Å) 6.7708 (1), 17.2107 (2), 12.3465 (2)
β (°) 98.184 (1)
V3) 1424.09 (4)
Z 4
Radiation type Mo Kα
μ (mm−1) 2.90
Crystal size (mm) 0.32 × 0.19 × 0.13
 
Data collection
Diffractometer Bruker SMART APEX2 CCD
Absorption correction Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.628, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 32857, 3555, 3006
Rint 0.029
(sin θ/λ)max−1) 0.669
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.022, 0.057, 1.04
No. of reflections 3555
No. of parameters 202
No. of restraints 1
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.38, −0.31
Computer programs: APEX2 (Bruker, 2010[Bruker (2010). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT2013 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2018/3 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Structural data


Acknowledgements

The authors would like to thank the University of KwaZulu-Natal for the research facilities. DUT/HANT is acknowledged for funding the postdoctoral fellowship of HI.

References

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First citationKumar, S., Singh, P., Hundal, G., Singh Hundal, M. & Kumar, S. (2013). Chem. Commun. 49, 2667–2669.  CrossRef Google Scholar
First citationLee, H. M., Lu, C. Y., Chen, C. Y., Chen, W. L., Lin, H. C., Chiu, P. L. & Cheng, P. Y. (2004). Tetrahedron, 60, 5807–5825.  Web of Science CSD CrossRef CAS Google Scholar
First citationOtt, I. (2017). Medicinal Chemistry of Metal N-Heterocyclic Carbene (NHC) Complexes. In Inorganic and Organometallic Transition Metal Complexes with Biological Molecules and Living Cells, edited by K. K.-W. Lo, pp. 147–179. New York: Academic Press.  Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar

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ISSN: 2414-3146