Acta Crystallographica Section C

Crystal Structure Communications

Volume 61, Part 6 (June 2005)

organic compounds

gg1255 scheme

Acta Cryst. (2005). C61, o354-o357 [doi:10.1107/S0108270105011881]

Three structures containing (E)-1,2-bis(benzimidazol-2-yl)ethene groups

R. T. Stibrany, H. J. Schugar and J. A. Potenza

Abstract: Two of the title compounds, namely (E)-1,2-bis(1-methylbenzimidazol-2-yl)ethene, C₁₈H₁₆N₄, (Ib), and (E)-1,2-bis(1-ethylbenzimidazol-2-yl)ethene, C₂₀H₂₀N₄, (Ic), consist of centrosymmetric trans-bis(1-alkylbenzimidazol-2-yl)ethene molecules, while 3-ethyl-2-[(E)-2-(1-ethylbenzimidazol-2-yl)ethenyl]benzimidazol-1-ium perchlorate, C₂₀H₂₁N₄⁺·ClO₄^-, (II), contains the monoprotonated analogue of compound (Ic). In the three structures, the benzimidazole and benzimidazolium moieties are essentially planar; the geometric parameters for the ethene linkages and their bonds to the aromatic groups are consistent with double and single bonds, respectively, implying little, if any, conjugation of the central C=C bonds with the nitrogen-containing rings. The C-N bond lengths in the N=C-N part of the benzimidazole groups differ and are consistent with localized imine C=N and amine C-N linkages in (Ib) and (Ic); in contrast, the corresponding distances in the benzimidazolium cation are equal in (II), consistent with electron delocalization resulting from protonation of the amine N atom. Crystals of (Ib) and (Ic) contain columns of parallel molecules, which are linked by edge-over-edge C-H [bold pi] overlap. The columns are linked to one another by C-H interactions and, in the case of (Ib), C-HN hydrogen bonds. Crystals of (II) contain layers of monocations linked by - interactions and separated by both perchlorate anions and the protruding ethyl groups; the cations and anions are linked by N-HO hydrogen bonds.

Formula: C₁₈H₁₆N₄, C₂₀H₂₀N₄ and C₂₀H₂₁N ${_4}{^+}$ ·ClO ${_4}{^-}$


	Structure factor file (CIF format) (62.9 kbytes) Contains datablock Ib

	Structure factor file (CIF format) (72.2 kbytes) Contains datablock Ic

	Structure factor file (CIF format) (169.3 kbytes) Contains datablock tyyy4m

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