Inter-molecular inter-actions in a phenol-substituted benzimidazole.

Hydrogen bonding plays an important role in the design of solid-state structures and gels with desirable properties. 1-(4-Hydroxybenzyl)-2-(4-hydroxyphenyl)-5,6-dimethyl-1H-benzimidazole was isolated as the acetone disolvate, C22H20N2O2·2C3H6O. O-H⋯N hydrogen bonding between benz-imidazole mol-ecules results in chains parallel to [010]. One of the acetone solvate mol-ecules participates in O-H⋯O hydrogen bonding with the benzimidazole derivative. C-H⋯π inter-actions are observed in the extended structure. Hirshfeld surface analysis was used to explore the inter-molecular inter-actions and density functional theory was used to estimate the strength of the hydrogen bonds.

An exploration of O-H⋯O and C-H⋯π inter-actions in a long-chain-ester-substituted phenyl-phenol: methyl 10-[4-(4-hydroxyphenyl)phenoxy]decanoate.

An understanding of the driving forces resulting in crystallization vs organogel formation is essential to the development of modern soft materials. In the mol-ecular structure of the title compound, methyl 10-[4-(4-hydroxyphenyl)phen-oxy]decanoate (MBO10Me), C23H30O4, the aromatic rings of the biphenyl group are canted by 6.6 (2)° and the long-chain ester group has an extended conformation. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains along [10[Formula: see text]]. The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ac plane. The layers are linked by C-H⋯π inter-actions, forming a three-dimensional supra-molecular structure. The extended structure exhibits a lamellar sheet arrangement of mol-ecules stacking along the b-axis direction. Each mol-ecule has six nearest neighbors and the seven-mol-ecule bundles stack to form a columnar superstructure. Inter-action energies within the bundles are dominated by dispersion forces, whereas inter-columnar inter-actions have a greater electrostatic component.

Non-Steroidal Biphenyl Gelators: Correlation of Xerogel Structure with Solid-State Structure and Circular Dichroism Spectroscopy.

Because the factors favoring the formation of well-formed single crystals are dissimilar to those conducive to gel formation, few examples of single-crystal structural characterizations of organogelators are found in the literature. A series of biphenyl methyl and ethyl diester derivatives of varying chain length were synthesized and their gelation abilities explored. X-ray diffraction of single crystals of one of the gelators reveals a columnar extended structure. Based on XRD results for xerogels obtained from the reported organogelators, the members of the series are isostructural and so also adopt a columnar superstructure. Scanning electron microscopy (SEM) was used for the investigation of the morphology of the xerogels, which display either platelet-like morphologies or more typical entangled twisted ribbon-like aggregates. The gels exhibit chirality, which depends on the sol-gel transition history, as observed by induced circular dichroism (ICD) spectroscopy.

Structural characterization, gelation ability, and energy-framework analysis of two bis(long-chain ester)-substituted 4,4'-biphenyl compounds.

There are few examples of single-crystal structure determinations of gelators, as gel formation requires that the dissolved gelator self-assemble into a three-dimensional network structure incorporating solvent via noncovalent interactions rather than self-assembly followed by crystallization. In the solid-state structures of the isostructural compounds 4,4'-bis[5-(methoxycarbonyl)pentyloxy]biphenyl (BBO6-Me), C26H34O6, and 4,4'-bis[5-(ethoxycarbonyl)pentyloxy]biphenyl (BBO6-Et), C28H38O6, the molecules sit on a crystallographically imposed center of symmetry, resulting in strictly coplanar phenyl rings. BBO6-Me behaves as an organogelator in various alcohol solvents, whereas BBO6-Et does not. The extended structure reveals bundles of molecules that form a columnar superstructure. Framework-energy calculations reveal much stronger interaction energies within the columns (-52 to -78 kJ mol-1) than between columns (-2 to -16 kJ mol-1). The intracolumnar interactions are dominated by a dispersion component, whereas the intercolumnar interactions have a substantial electrostatic component.

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

The synthesis of a novel benzimidazole derivative with a long-chain-ester substituent, namely methyl 8-[4-(1H-benzimidazol-2-yl)phenoxy]octanoate, (3), is reported. Ester (3) shows evidence of aggregation in solution and weak gelation ability with toluene. The octan-1-ol solvate, methyl 8-[4-(1H-benzimidazol-2-yl)phenoxy]octanoate octan-1-ol monosolvate, C22H26N2O3·C8H18O, (4), exhibits a four-molecule hydrogen-bonded motif in the solid state, with N-H...O hydrogen bonds between benzimidazole molecules and O-H...N hydrogen bonds between the octan-1-ol solvent molecules and the benzimidazole unit. The alkyl chains of the ester and the octan-1-ol molecules are in unfolded conformations. The phenylene ring is canted by 10.27 (6)° from the plane of the benzimidazole ring system. H...C contacts make up 20.7% of the Hirshfeld surface coverage. Weak C-H...π interactions involving the benzimidazole alkyl chain and three aromatic rings are observed.

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

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.

Synthesis and spectroscopic characterization of chiral biphenyl-cholesterol gels.

The synthesis of 4-(3-cholesteroxycarbonylpropyloxy)biphenyl (BO4-chol), 4-(7-cholesteroxycarbonylheptyloxy)biphenyl (BO8-chol), and 4,4'-bis(7-cholesteroxycarbonyl heptyloxy)biphenyl (BBO8-chol) is reported. These gelators form 1% and 2% (w/w) stable gels in n-octanol. The gels formed from single cholesterol gelators (BO4-chol and BO8-chol) exhibit lower phase transition temperatures (Tg) (62-65, 68-69 °C) than the gel obtained from the bischolesterol gelator BBO8-chol (96-98 °C). All three gelators form chiral gels in n-octanol as observed by induced circular dichroism (ICD) spectroscopy. The effect of two cholesterol moieties versus one cholesterol unit linked to a biphenyl molecule by a flexible chain, and the effect of the chain length on the gelation ability of these three novel gelators was investigated by circular dichroism (CD), absorption, and fluorescence spectroscopies. The gels obtained from BO4-chol and BO8-chol exhibit biphasic circular dichroism spectra with opposite chirality. The ICD spectra of both BO8-chol and BBO8-chol gels show a positive ICD band followed by a negative band at room temperature. However, while BO8-chol gel ICD absorptions decrease equally as temperature increases, BBO8-chol gel shows an inversion of the Cotton effect bands between 50 and 60 °C until completely disappearing above the phase transition temperature. SEM was used for the investigation of the morphology of the xerogels. On the basis of XRD data and molecular modeling, we propose packing modes for the formation of the organogelator aggregates.

4-Bromo-2-(5-bromo-thio-phen-2-yl)-1-[(5-bromo-thio-phen-2-yl)meth-yl]-5,6-dimethyl-1H-benzimidazole.

The title compound, C18H13Br3N2S2, was obtained via the reaction of N-bromo-succinamide with 5,6-dimethyl-2-(thio-phen-2-yl)-1-[(thio-phen-2-yl)meth-yl]-1H-benzimidazole. The compound exhibits rotational disorder of the 5-bromo-thio-phen-2-yl substituent with a refined major:minor occupancy ratio of 0.876 (7):0.124 (7). The 5-bromo-thio-phen-2-yl mean plane is canted to the benzimidazole plane by 20.0 (4) and 21 (4)° in the major and minor components, respectively. In the crystal, weak C-H⋯N inter-actions link the mol-ecules into infinite C(7) chains along the 21 axes.

Thio-phene-2-carbaldehyde azine.

The asymmetric unit of the title compound, C10H8N2S2, is composed of two independent half-mol-ecules, each residing on a center of symmetry. In the crystal, weak C-H⋯π inter-actions join the two symmetry-independent molecules together into interlinked chains parallel to [011]. The crystal structure was refined as a two-component pseudo-merohedral twin using the twin law 001 0-10 100. The refined domain fractions are 0.516 (3) and 0.484 (3).

2-Amino-5-nitro-N-[(E)-thio-phen-2-yl-methyl-idene]aniline.

In the title mol-ecule, C(11)H(9)N(3)O(2)S, the thio-phene and benzene rings form a dihedral angle of 17.68 (9)°. The thio-phene S atom and the imine N atom are syn with respect to each other. In the crystal, N-H⋯O and N-H⋯N hydrogen bonds connect mol-ecules, forming a two-dimensional network parallel to (10-1).

2-(Furan-2-yl)-1,3-bis(furan-2-ylmeth-yl)-1H-benzimidazol-3-ium chloride monohydrate.

The title hydrated salt, C(21)H(17)N(2)O(3) (+)·Cl(-)·H(2)O, exhibits disorder in one of the furan rings. The major and minor components have a refined occupancy ratio of 0.844 (19):0.156 (19). The structure displays intermolecular hydrogen bonding involving the water molecule and the chloride anion. Close intermolecular C-H⋯Cl and C-H⋯(furan ring) inter-actions complete the hydrogen bonding.

2-(Thio-phen-2-yl)-1-(thio-phen-2-ylmeth-yl)-1H-benzimidazole.

In the title compound, C(16)H(12)N(2)S(2), the thio-phene groups are rotationally disordered over two sets of sites, by approximately 180°, with occupancy ratios of 0.916 (2):0.084 (2) and 0.903 (2):0.097 (2). The major components of the thio-phene and methyl-ene substituted thio-phene rings are canted by 24.06 (12) and 85.07 (10)°, respectively, from the benzimidazole ring system plane and the dihedral angle between the major component thio-phene ring planes is 84.90 (14)°. In the crystal, there is a weak C-H⋯N hydrogen bond which links mol-ecules into chains.