Benzimidazole Units Research Articles

Hydrogen‐Bonding Interactions and Molecular Packing in Polyimide Fibers Containing Benzimidazole Units

Rigid‐rod polyimides (PI) containing benzimidazole moieties were synthesized and spun into fibers by a wet‐spinning method. The resultant fibers exhibited an optimum tensile strength of 2.15 GPa and an initial modulus of 105 GPa with a low elongation of 2.2%. The PI fibers consisting of various ratios of 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl (TFMB) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA) were investigated by Fourier transform infrared spectroscopy and two‐dimensional wide angle X‐ray diffraction (2D WAXD). Direct evidence of hydrogen‐bonding involving the NH groups of BIA and the imide carbonyls is presented. Qualitative and quantitative information of this molecular interaction was obtained and discussed. This has been considered as a main factor responsible for the significantly improved mechanical properties of the PI fibers. 2D WAXD and molecular mechanics modeling were used to simulate the structure of the aromatic PI fibers. As a result, the addition of BIA in the main chains is to increase the regularity of the molecule packing, which plays an important role in the enhanced strength of the PI fibers with more BIA loadings.

5,6-Dimethyl-2-(5-methyl-thio-phen-2-yl)-1-[(5-methyl-thio-phen-2-yl)meth-yl]-1H-benzimidazole.

The title mol­ecule, C20H20N2S2, is T-shaped and consists of a nearly flat 5,6-dimethyl-2-(5-methyl­thio­phen-2-yl)benzimidazole system approximately perpendicular to the 5-methyl­thio­phen-2-ylmethyl substituent. The 5,6-dimethyl-2-(5-meth­yl­thio­phen-2-yl)benzimidazole system is rotationally disordered about the two imidazole N atoms as approximated by a twofold rotation axis with a refined major/minor occupancy ratio of 0.884 (2):0.116 (2). The benzimidazole ring system is essentially planar, the largest deviations being 0.026 (2) and 0.044 (18) Å in the major and minor components, respectively. The inter­planar angles between the benzimidazole unit and the 5-methyl­thio­phen-2-yl substituent are 10.8 (3) and 8(3)° in the major and minor components, respectively, and the corresponding angles with the 5-methyl­thio­phen-2-ylmethyl substituent are 88.12 (8) and 89.5 (4)°. In the crystal, mol­ecules are oriented with their 2-(5-methyl­thio­phen-2-yl)benzimidazole mean planes approximately parallel to (11) and appear to be held together by π–π [2-thiophene⋯imidazole centroid–centroid distance = 4.1383 (7) Å] and C—H⋯π contacts. A weak C—H⋯N hydrogen bond generates infinite chains parallel to [100].

1-(4-Fluoro-benz-yl)-2-(pyridin-2-yl)-1H-benzimidazole.

In the title compound, C19H14FN3, the dihedral angles between the benzimidazole unit (r.m.s. deviation= 0.017 Å) and the pyridine and benzene rings are 24.46 (4) and 81.87 (3)°, respectively. In the crystal, mol­ecules are stacked along the a-axis direction by C—H⋯π inter­actions.

Boron-Dipyrromethene Based Reversible and Reusable Selective Chemosensor for Fluoride Detection

We synthesized benzimidazole substituted boron-dipyrromethene 1 (BODIPY 1) by treating 3,5-diformyl BODIPY 2 with o-phenylenediamine under mild acid catalyzed conditions and characterized by using various spectroscopic techniques. The X-ray structure analysis revealed that the benzimidazole NH group is involved in intramolecular hydrogen bonding with fluoride atoms which resulted in a coplanar geometry between BODIPY and benzimidazole moiety. The presence of benzimidazole moiety at 3-position of BODIPY siginificantly altered the electronic properties, which is clearly evident in bathochromic shifts of absorption and fluorescence bands, improved quantum yields, increased lifetimes compared to BODIPY 2. The anion binding studies indicated that BODIPY 1 showed remarkable selectivity and specificity toward F(-) ion over other anions. Addition of F(-) ion to BODIPY 1 resulted in quenching of fluorescence accompanied by a visual detectable color change from fluorescent pink to nonfluorescent blue. The recognition mechanism is attributed to a fluoride-triggered disruption of the hydrogen bonding between BODIPY and benzimidazole moieties leading to (i) noncoplanar geometry between BODIPY and benzimidazole units and (ii) operation of photoinduced electron transfer (PET) from benzimidazole moiety to BODIPY unit causing quenching of fluorescence. Interestingly, when we titrated the nonfluorescent blue 1-F(-) solution with TFA resulted in a significant enhancement of fluorescence intensity (15-fold) because the PET quenching is prevented due to protonation of benzimidazole group. Furthermore, the reversibility and reusability of sensor 1 for the detection of F(-) ion was tested for six cycles indicating the sensor 1 is stable and can be used in reversible manner.

Investigation of photophysical properties of new branched compounds with triazine and benzimidazole units

Three new acceptor–donor–acceptor branched compounds with triazine and benzimidazole units (M1, M2, and M3) were synthesized and characterized by infrared, hydrogen-1 nuclear magnetic resonance, carbon-13 nuclear magnetic resonance, mass spectrometry, and elemental analysis. Their photophysical properties were investigated including linear absorption, single-photon excited fluorescence, fluorescence quantum yield, two-photon absorption, and frequency up-converted fluorescence. When the number of branches increases, the spectral positions of the linear absorption and the single-photon excited fluorescence show red shifts, while the fluorescence quantum yields decrease. When the polarity of solvents increases, the spectral positions of the single-photon excited fluorescence and the Stokes shifts also show red shifts, while the fluorescence quantum yields of the two-branched compound (M2) and three-branched compound (M3) decrease. Under the excitation of an 800 nm laser with a pulse width of 80 fs, all these compounds emit intense green frequency up-converted fluorescence, and the two-photon absorption cross-sections are 210, 968, and 1613 GM for M1, M2, and M3, respectively. This result shows that significant enhancement of the two-photon absorption cross-section can be achieved by sufficient electronic coupling between the strong charge transfer acceptor–donor–acceptor quadrupolar branches through the s-triazine core.

A water-soluble highly sensitive and selective fluorescent sensor for Hg2+ based on 2-(2-(8-hydroxyquinolin)-yl)benzimidazole via ligand-to-metal charge transfer (LMCT)

A water-soluble fluorescent sensor (L) based on 2-(2-(8-hydroxyquinolin)-yl)benzimidazole has been synthesized and characterized. Sensor L displays highly selective and sensitive recognition of Hg2+ with a fluorescence “ON–OFF” response in buffered aqueous solution (1% dimethyl sulfoxide (DMSO), Tris–HCl 10 mM, pH = 7.4). X-ray crystal structure of the L–Hg2+ complex reveals that the oxygen and nitrogen atoms of 8-hydroxyquinoline and the imine N atom of the benzimidazole unit (N1) bind Hg2+ through a 1 : 1 binding stoichiometry. The fluorescence quenching mechanism is qualitatively evaluated by quantum chemical calculations which show that the fluorescence quenching phenomenon is caused by ligand-to-metal charge transfer (LMCT) in the excited state.

New insights into carbon dioxide interactions with benzimidazole-linked polymers

A synergistic experimental and theoretical study (DFT) highlights the impact of material design at the molecular and electronic levels on the binding affinity and interaction sites of CO2 with benzimidazole-linked polymers (BILPs); CO2 is stabilized by benzimidazole units through Lewis acid-base (N···CO2) and aryl C-H···O=C=O interactions.

Synthesis and Characterization of Trifluoromethylated Benzimidazole and Benzo[1,2-B:3,4-B']Dithiophene Based Donor-Acceptor Conjugated Polymer for Polymer Solar Cells

ABSTRACTA new donor-acceptor structured conjugated polymer (PDODTBI) with trifluoromethylated benzimidazole and benzo[1,2-b;3,4-b']dithiophene (BDT) unit have been designed and synthesized using Stille coupling polymerization reaction. The polymer is highly soluble in common organic solvents such as chloroform, tetrahydrofuran and chlorobenzene with good film forming properties. The structure of the polymer is elucidated by 1H NMR and FTIR spectroscopic techniques. The introduction of a trifluoromethyl group at 4th position of the benzimidazole unit has significantly altered the optical and electrochemical properties of polymer. Polymer film showed broad absorption band in the range of 400-680 nm. Optical band gap of the polymer estimated from the absorption band edge and is found to be ∼1.88 eV. Polymer exhibited deeper HOMO (-5.0 eV) and the LUMO (-3.12 eV) energy levels. Bulk heterojunction (BHJ) solar cell device with PDODTBI as a donor and PC61BM as an acceptor were evaluated.

2-(Naphthalen-1-yl)-1-phenyl-1H-benzimidazole benzene hemisolvate

In the title compound, C23H16N2·0.5C6H6, the benzimidazole unit [maximum deviation = 0.0258 (6) Å] and the naphthalene ring system [maximum deviation = 0.0254 (6) Å] are both essentially planar and make a dihedral angle of 61.955 (17)°. The imidazole ring makes dihedral angle of 61.73 (4)° with the phenyl ring. An intra­molecular C—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal, seven weak C—H⋯π inter­actions involving the fused ring system, the benzene solvent mol­ecule, the imidazole phenyl rings are observed, leading to a three-dimensional architecture.

Stable benzimidazole-incorporated porous polymer network for carbon capture with high efficiency and low cost

Porous Polymer Networks (PPNs) are an emerging category of advanced porous materials that are of interest for carbon dioxide capture due to their great stabilities and convenient functionalization processes. In this work, an intrinsically-functionalized porous network, PPN-101, was prepared from commercially accessible materials via an easy two-step synthesis. It has a BET surface area of 1095 m2/g. Due to the presence of the benzimidazole units in the framework, its CO2 uptake at 273 K reaches 115 cm3/g and its calculated CO2/N2 selectivity is 199, which indicates its potential for CO2/N2 separation. The great stability, large CO2/N2 selectivity and low production cost make PPN-101 a promising material for industrial separation of CO2 from flue gas. Its H2 and CH4 uptake properties were also investigated.

Amino[(1H-benzimidazol-2-yl)amino]methaniminium 4-methylbenzenesulfonate

The asymmetric unit of the title salt, C8H10N5 +·C7H7O3S−, consists of two amino­[(1H-benzimidazol-2-yl)amino]­meth­an­im­inium cations and two 4-methyl­benzene­sulfonate anions. The cations are each stabilized by intra­molecular N—H⋯N hydrogen bonds between the free amino groups and the imine N atoms of the benzimidazole units, forming S(6) ring motifs. In the crystal, cations and anions are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular framework. Two strong π–π stacking inter­actions [centroid–centroid distances = 3.4112 (14) and 3.4104 (14) Å] also occur between the centroids of the imidazole rings of like cations.

2-(4-Hy-droxy-phen-yl)-1H-benzimidazol-3-ium chloride monohydrate.

The title mol­ecular salt, C13H11N2O+·Cl−·H2O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4)°. The chloride anion and benzimidazole cation are linked by two N+—H⋯Cl− hydrogen bonds, forming chains propagating along [010]. These chains are linked through O—H⋯Cl hydrogen bonds involving the water mol­ecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (10-2). Two π–π inter­actions involving the imidazolium ring with the benzene and phenol rings [centroid–centroid distances = 3.859 (3) and 3.602 (3) Å, respectively], contribute to this second dimension. A strong O—H⋯O hydrogen bond involving the water mol­ecule and the phenol substituent on the benzimidazole unit links the networks, forming a three-dimensional structure.

Synthesis and cell localization of self-assembled dinuclear lanthanide bioprobes

Lanthanide bioprobes and bioconjugates are ideal luminescent stains in view of their low propensity to photobleaching, sharp emission lines and long excited state lifetimes permitting time-resolved detection for enhanced sensitivity. In this paper, we expand our previous work which demonstrated that self-assembled dinuclear triple-stranded helicates [Ln2(L(C2X))3] behave as excellent cell and tissue labels in immunocytochemical and immunohistochemical assays. The synthetic strategy of the hexadentate ditopic ligands incorporating dipicolinic acid, benzimidazole units and polyoxyethylene pendants is revisited in order to provide a more straightforward route and to give access to further functionalization of the polyoxyethylene arms by incorporating a terminal function X. Formation of the helicates [Ln2(L(C2X))3] (X=COOH, CH2OH, COEt, NH2, phthalimide) is ascertained by several experimental techniques and their stability tested against diethylenetriaminepentaacetate. Their photophysical properties (quantum yield, lifetime, radiative lifetime and sensitization efficiency) are presented and compared with those of the parent helicates [Ln2(L(C2))3]. Finally, the cellular uptake of five Eu(III) helicates is monitored by time-resolved luminescence microscopy and their localization in HeLa cells established by co-staining experiments.

1-(2,6-Diisopropylphenyl)-1H-benzimidazole

In the title compound, C19H22N2, both the benzimidazole unit and the 2,6-diiso­propyl­phenyl group are essentially planar [maximum deviations from the least-squares planes of 0.005 (1) and 0.009 (1) Å, respectively]. The dihedral angle between the two planes is 79.6 (7)°. In the crystal, mol­ecules are linked into chains along the a-axis direction by weak C—H⋯N inter­actions. The crystal structure also features C—H⋯π inter­actions, which link the chains into a three-dimensional network.

New host materials based on fluorene and benzimidazole units for efficient solution-processed green phosphorescent OLEDs

New green host materials 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole and 1-(9,9′-spirobifluorene-2-yl)-2-phenyl-1H-benzimidazole for solution-processed green phosphorescent organic light-emitting devices have been designed and synthesized by attaching the electron transporting benzimidazole units to the rigid fluorene units. Owing to the non-planar structures, which decrease the π conjugation length of fluorene and benzimidazole rings, these fluorene derived derivatives show high triplet energy. The high triplet energy of newly host materials ensures efficient energy transfer from the host to the triplet emitter tris(2-phenylpyridine)iridium. Furthermore, the thermal, photophysical, electrochemical properties and crystal structures of 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole and 1-(9,9′-spirobifluorene-2-yl)-2-phenyl-1H-benzimidazole were investigated. The solution-processed single-layer green device using 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole as the host for the phosphorescence emitter tris(2-phenylpyridine)iridium showed the maximum luminance efficiencies of 10.1cd/A. This result demonstrated that the newly synthesized, fluorene-based rigid host materials are advantageous for fabrication of highly efficient green phosphorescent organic light-emitting diodes.

The Origin of the Emission Properties of π-Conjugated Molecules that have an Acid-responsive Benzimidazole Unit

The photophysical properties, especially the emission properties, of π-conjugated molecules with an acid-responsive N-methylbenzimidazole unit have been characterized and compared between T-shaped cross-conjugated and linear conjugated molecules. X-ray crystal structures and optimized structures based on DFT calculations suggest a planar conformation of the 2-thienyl-N-benzimidazole structure even after protonation where intramolecular S–N and NH–S interactions, respectively, are responsible for the stabilization of planar structures. Despite the planarity in the ground state, the T-shaped cross-conjugated molecules exhibit the twisted intramolecular charge-transfer (TICT) emission in response to protonation, whereas the corresponding linear conjugated molecule without a horizontal π-system does not have a charge-transfer state. The difference in the separation of frontier molecular orbitals of the HOMO and LUMO and the energy barrier of the rotation about the thienyl ring predicted by the DFT calculations accounts for the difference in the emission decay process between the linear and cross-conjugated molecules with a protonated benzimidazole unit. An orthogonally allocated π-conjugated system appears to be essential for the emergence of TICT characteristics upon protonation in terms of the separation of molecular orbitals of the HOMOs and LUMOs, as well as the ease of rotation.

Computational Study on Triphenylamine-Based Dyes Containing Benzimidazole Units for Dye-Sensitized Solar Cells

Three novel dyes (D1, D2 and D3) containing triphenylamine (TPA) unit as core and bearing different benzimidazole units as secondary electron-donors are designed. The geometries, electronic structures, and electronic absorption spectra of these dyes are studied by DFT and TD-DFT. The optimized results indicate that these dyes are all non-coplanar, which can help to inhibit the close intermolecular π-π stacking aggregation effectively. The lowest unoccupied molecular orbital (LUMO) energy levels of the dyes are higher than the conduction band edge of the TiO2, which ensures a high efficiency of electron transfer from these dyes to TiO2 electrode. As the highest occupied molecular orbital (HOMO) energy levels of these dyes are lower than those of I-/I-3, these molecules that lose electrons could be restored by getting electrons from electrolyte. The absorption spectra of these dyes are simulated, and the calculated results indicate that D3 can absorb more photons than those of D1, D2 and TPAR in the region from 250 to 580 nm, which should have the best performance of photo-to-electric conversion efficiency.

Synthesis and mesomorphic properties of 2-(4′-alkoxybiphenyl-4-yl)-1H-benzimidazole derivatives

Three series of 2-(4′-alkoxybiphenyl-4-yl)-1H-benzimidazole derivatives (nM-x), which possessed 5-nitrobenzimidazole (nM-N series), benzimidazole (nM-H series) or 5-methylbenzimidazole (nM-M series) units at the end of the molecule, were synthesised and characterised by infrared, 1H- and 13C-nuclear magnetic resonance spectra, electrospray ionisation-mass spectrometry and elemental analysis. Their phase transition behaviour was investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. All the compounds exhibited enantiotropic smectic mesophases with wide temperature domains for a carbon number in the alkoxy chain from 6 to 16, where the mesophase ranges were 14–91°C and 17–99°C during heating and cooling processes for the nM-N compounds, 7–25°C and 8–49°C for the nM-H compounds and 48–81°C and 52–85°C for the nM-M compounds, respectively. The effect of the length of alkoxy chain on mesomorphic properties was discussed. The nM-N and nM-M exhibited a much wider mesophase range whether during heating or cooling process than the corresponding nM-H series, especially for the longer terminal chain (n > 8), which indicated that the substituent in the benzimidazole moiety was helpful in increasing the mesophase stability.

One step synthesis of pyrido[1,2-a]benzimidazole derivatives of aryloxypyrazole and their antimicrobial evaluation

Abstract A new series of pyrido[1,2- a ]benzimidazole derivatives bearing the aryloxypyrazole nucleus have been synthesized by base-catalyzed cyclocondensation reaction through multi-component reaction (MCR) approach. All the synthesized compounds were investigated against a representative panel of pathogenic strains using broth microdilution minimum inhibitory concentration (MIC) method for their in vitro antimicrobial activity. Reviewing the data, majority of the compounds were found to be active against employed pathogens. SAR study explores that antimicrobial activity is strongly depends on the nature of the substituents at the ether linked aryl ring attached to the pyrazole unit, together with the substituent present on the C 5 of the benzimidazole unit.

Further investigation of intramolecular H-bonding in benzimidazole and EDOT containing monomer

Density functional theory (DFT) calculations of the relative stabilities and harmonic vibrational spectra of four different conformers of 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-phenyl-1H-benzo[d]imidazole (BImBEd) are presented and compared with experimental IR data. BImBEd, containing phenyl substituted benzimidazole as the acceptor and 3,4-ethylenedioxythiophene (EDOT) as the donor unit, was electrochemically polymerized in different pH media earlier. Electronic states of nitrogen in benzimidazole unit of synthesized polymeric films were analyzed via X-ray photoelectron spectroscopy. Both DFT and XPS results suggest the presence of an intramolecular H-bond between the amine of the imidazole and the oxygen of the EDOT molecules. Additionally, the quantity of the H-bond can be controlled via treatment of an acid (trifloroacetic acid) and a base (sodium hydroxide) as we stated in our previous study.