Structure determination of three furan-substituted benzimidazoles and calculation of π–π and C—H...π interaction energies

Abstract

The synthesis and structural characterization of 2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazole [C16H12N2O2, (I)], 2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazol-3-ium chloride monohydrate [C16H13N2O2(+)·Cl(-)·H2O, (II)] and the hydrobromide salt 5,6-dimethyl-2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzimidazol-3-ium bromide [C18H17N2O2(+)·Br(-), (III)] are described. Benzimidazole (I) displays two sets of aromatic interactions, each of which involves pairs of molecules in a head-to-tail arrangement. The first, denoted set (Ia), exhibits both intermolecular C-H···π interactions between the 2-(furan-2-yl) (abbreviated as Fn) and 1-(furan-2-ylmethyl) (abbreviated as MeFn) substituents, and π-π interactions involving the Fn substituents between inversion-center-related molecules. The second, denoted set (Ib), involves π-π interactions involving both the benzene ring (Bz) and the imidazole ring (Im) of benzimidazole. Hydrated salt (II) exhibits N-H···OH2···Cl hydrogen bonding that results in chains of molecules parallel to the a axis. There is also a head-to-head aromatic stacking of the protonated benzimidazole cations in which the Bz and Im rings of one molecule interact with the Im and Fn rings of adjacent molecules in the chain. Salt (III) displays N-H···Br hydrogen bonding and π-π interactions involving inversion-center-related benzimidazole rings in a head-to-tail arrangement. In all of the π-π interactions observed, the interacting moieties are shifted with respect to each other along the major molecular axis. Basis set superposition energy-corrected (counterpoise method) interaction energies were calculated for each interaction [DFT, M06-2X/6-31+G(d)] employing atomic coordinates obtained in the crystallographic analyses for heavy atoms and optimized H-atom coordinates. The calculated interaction energies are -43.0, -39.8, -48.5, and -55.0 kJ mol(-1) for (Ia), (Ib), (II), and (III), respectively. For (Ia), the analysis was used to partition the interaction energies into the C-H···π and π-π components, which are 9.4 and 24.1 kJ mol(-1), respectively. Energy-minimized structures were used to determine the optimal interplanar spacing, the slip distance along the major molecular axis, and the slip distance along the minor molecular axis for 2-(furan-2-yl)-1H-benzimidazole.

Hydrogen bonding and π–π interactions in the cocrystal salt [Fe(bpe)2(H2O)4](TCEP)2·2(bpe) [bpe is trans-1,2-bis(pyridin-4-yl)ethene and TCEP is 1,1,3,3-tetracyano-2-ethoxypropenide]

“…Each of theinteractions found in Table 4 involved two rings from each of two bpe moieties. The results obtained for the two --only interactions compare favorably with the value 11.9 kJ mol À1 reported for a single pyridyl moiety with the benzene ring of phenylalanine as found in HIV-1 protease complexed to atazanavir (Huber et al, 2014;Klei et al, 2007), and the 24.1 kJ mol À1 interaction energy for a benzimidazole derivative exhibiting furan rings in a slipped coplanar arrangement (Geiger et al, 2014). The increase in the number of aromatic rings involved has been shown to result in a more favorable interaction: for sandwiched pairs of benzene, napththalene, anthracene, and tetracene, interaction energies of À11, À28, À48, and À68 kJ mol À1 , respectively, were calculated (Grimme, 2008).…”

Hydrogen bonding in two benzene-1,2-diaminium pyridine-2-carboxylate salts and a cocrystal of benzene-1,2-diamine and benzoic acid

“…The C-HÁ Á Á (À12.1 kJ mol À1 ) and -(À17.8 kJ mol À1 ) interactions are dominated by the dispersion energy. Although much weaker than the calculated traditional hydrogen-bond energies, these values compare favorably with the value of À7.7 kJ mol À1 for a C-HÁ Á Á interaction between furan molecules (Geiger, Geiger & Deck, 2014) and the À9.4 kJ mol À1 reported for a 'T-shaped' benzene dimer (Sherrill et al, 2009). A value of À20.7 kJ mol À1 was reported for ainteraction between benzene rings of a benzimidazole derivative (Geiger, Geiger & Deck, 2014) and À11 kJ mol À1 for benzene rings in a coplanar orientation (Grimme, 2008).…”

Synthesis and characterization of a novel long-alkyl-chain ester-substituted benzimidazole gelator and its octan-1-ol solvate

“…For the Im ring, the closest approach is H16AÁ Á ÁC7 ii = 2.99 Å [C16Á Á ÁC7 ii = 3.839 (2) Å and C16-H16AÁ Á ÁC7 ii = 144 ], with a 2.93 Å H16A-to-ring plane distance. Contrary to expectations, there are no significantinteractions, as have been found in other benzimidazole derivatives Geiger, Geiger & Deck, 2014;Krawczyk & Gdaniec, 2005;Geiger & Isaac, 2014;El Ghozlani et al, 2014;Yeong et al, 2013;Fathima et al, 2013;Krishnamurthy et al, 2013;Yeong et al, 2013). The closest CgÁ Á ÁCg distance is Cg(Ph)Á Á ÁCg(Bz) ii of 5.0499 (14) Å .…”