Benzimidazole Units Research Articles

Aramid fiber with excellent interfacial properties suitable for resin composite in a wide polarity range

The weak interfacial adhesion of aramid fiber with resin matrix is believed as a major limitation for its wide application. In this study, a nondestructive grafting method was applied for surface modification of benzimidazole-contained aramid fiber. Using the NH in benzimidazole unit as active sites, aramid fiber surface was firstly decorated with densely SiO2 structure, and a rough surface was obtained. Then, high density of NH2 and C=C groups were introduced on fiber surface by the reaction with silane coupling agents. These functionalized NH2/C=C groups endow the fiber with the ability to chemically bonding with resin in a wide polarity range, including rubber, bismaleimide and epoxy resin. Also, the SiO2-decorated rough surface improves the level of mechanical interlocking with them. Experimental results show that the interfacial shear strength of functionalized fiber with natural rubber, bismaleimide and epoxy resin correspondingly increases 117%, 166% and 43%, compared with that of untreated fibers. Meanwhile, the grafting method is confirmed as nondestructive, and the superior mechanical property of aramid fiber is preserved. In all, the study presents a new effective method for the preparation of aramid fiber with excellent interfacial properties suitable for resin composite in a wide polarity range.

Synthesis and electropolymerization of tetra-[β-(2-benzimidazole)] and tetra-[β-(2-(1-(4- aminophenyl))benzimidazole)] embedded cobalt phthalocyanine and their supercapacitance behaviour

Novel polar, electroactive N4 macrocycle with four benzimidazole units covalently substituted to the periphery of the Cobalt(II)phthalocyanine complexes have been reported for the first time. Cobalt phthalocyanine with tetra[β-(2-benzimidazole)] and tetra[β-(2-(1-(4-aminophenyl))benzimidazole)] substituted complexes were synthesized from cobalt-tetra[β-(carboxylicacid)]phthalocyanine. Dark green coloured complexes were characterized by elemental analysis, UV-Vis, FT-IR, and X-ray powder diffraction for their purity. Thermal stability studies of these newly synthesized complexes revealed that these complexes are thermally highly stable.Electrochemical properties of the synthesized phthalocyanines were determined by cyclic voltammetry. CoII metal ion in the core of the cobalt-tetra [β-(2-benzimidazole)]phthalocyanine and cobalt-tetra[β-(2-(1-(4-aminophenyl))benzimidazole)] phthalocyanine complexes showed redox active behavior. Benzimidazole ring and –NH2 group in the complexes undergoes electrochemical polymerization on the working electrode during the positive potential sweeps. Electrochemical measurements of the monomer and polymeric films showed two redox couples which are assigned to the metal and ligand. The influence of reduced grapheneoxide intercalation on the supercapacitance behavior of the electropolymerized films has been studied and their supercapacitance values have been reported.

A Naked-Eye Colorimetric Receptor for Anions Based on Nitro Group Featuring with Benzimidazole Unit

A Naked-Eye Colorimetric Receptor for Anions Based on Nitro Group Featuring with Benzimidazole Unit

A pyrene-benzimidazole composed effective fluoride sensor: potential mimicking of a Boolean logic gate

A highly selective fluoride sensor based on a pyrene benzimidazole unit was developed and studied for recyclable memory function.

Cyclometalated N-heterocyclic carbene iridium(iii) complexes with naphthalimide chromophores: a novel class of phosphorescent heteroleptic compounds.

A series of cyclometalated N-heterocyclic carbene complexes of the general formula [Ir(C^N)2(C^C:)] has been prepared. Two sets of compounds were designed, those where (C^C:) represents a bidentate naphthalimide-substituted imidazolylidene ligand and (C^N) = ppy (3a), F2ppy (4a), bzq (5a) and those where (C^C:) represents a naphthalimide-substituted benzimidazolylidene ligand and (C^N) = ppy (3b), F2ppy (4b), bzq (5b). The naphthalimide-imidazole and naphthalimide-benzimidazole ligands 1a,b and the related imidazolium and benzimidazolium salts 2a,b were also prepared and fully characterized. The N-heterocyclic carbene Ir(iii) complexes have been characterized by NMR spectroscopy, cyclic voltammetry and elemental analysis. Moreover, the molecular structures of one imidazolium salt and four Ir(iii) complexes were determined by single-crystal X-ray diffraction. The structures provide us with valuable information, most notably the orientation of the naphthalimide chromophore with respect to the N-heterocyclic carbene moiety. All compounds are luminescent at room temperature and in a frozen solvent at 77 K, exhibiting a broad emission band that extends beyond 700 nm. The presence of the naphthalimide moiety changes the character of the lowest excited state from 3MLCT to 3LC, as corroborated by DFT and TD-DFT calculations. Remarkably, replacing imidazole with a benzimidazole unit improves the quantum yields of these compounds by decreasing the knr values which is an important feature for optimized emission performance. These studies provide valuable insights about a novel class of N-heterocyclic carbene-based luminescent complexes containing organic chromophores and affording metal complexes emitting across the red-NIR range.

Reduced efficiency roll-off and enhanced excition confinement in exciplex-type host: Electron transport materials based on benzimidazole units

Two high triplet energy electron transporting materials, tris(3-(1H-benzo[d]imidazol-2-yl)phenyl)benzene (BMZ-TB) and tris(3-(1H-benzo[d]imidazol-2-yl)phenyl)triazine (BMZ-TZ), were successfully designed and synthesized by Suzuki coupling reaction to form efficient exciplexes with the commonly used hole-transporting molecules, 4,4′,4″-tris[3-methylphenyl(phenyl)amino]-triphenylamine (m-MTDATA), 1,1-bis[4-[N,N-di(p-tolyl)-amino]phenyl]-cyclohexane (TAPC) and tris(4-carbazoyl-9-ylphenyl)-amine (TCTA). The optical, electrochemical, thermal and device properties of BMZ-TB and BMZ-TZ were systematically characterized. In comparison, Ir(mppy)3 based device host with TCTA:BMZ-TZ had high performance, showing a very low efficiency roll-off with the current efficiency of 24.9 cd A−1 at 1000 cd m−2, 23.7 cd A−1 at 5000 cd m−2, and 22.0 cd A−1 at 10000 cd m−2. Furthermore, systematic study of the excited-state dynamics found that the excessively high or low triplet energy of exciplex would induce a serious energy leakage from the complex state to the constituting molecule or from guest material to the exciplex state.

Novel Benzimidazole‐Containing Heterocyclic Compounds: Synthesis, Physical Properties and OLED Application

AbstractThree novel heterocyclic compounds containing one (M1) or two (isomers M2 and M3) benzimidazole units have been synthesized and fully characterized. The isomers M2 and M3 could be easily separated by column chromatography. Studies showed that the decrease of intermolecular π‐π stackings could enhance the fluorescence intensity of target compounds obviously. The single‐site compound M1 shows the lowest fluorescent quantum yield (ΦM1=0.013) in CH2Cl2 than that of the double‐site isomers M2 (anti‐type, ΦM2=0.148) and M3 (syn‐type, ΦM3=0.053). Electroluminescent performances of M2 and M3 in organic light‐emitting diodes were studied. As expected, M2 exhibits more than 2 times higher current efficiency than M3 with M2 showing a maximum current efficiency of 7.8 cd/A as compare to 3.6 cd/A for M3.

Benzimidazole as a structural unit in fluorescent chemical sensors: the hidden properties of a multifunctional heterocyclic scaffold

Benzimidazole (BI) derivatives are structurally similar to naturally occurring nucleotides, a fact that enables their use as scaffolds in biologically active organic synthetic compounds. However, BI can serve as a multifunctional unit in heteroaromatic molecular systems for optoelectronics and non-linear optics, photovoltaics, and in sensing and bioimaging. Its many structure-related properties such as electron accepting ability, π-bridging, chromogenic pH sensitivity/switching and metal-ion chelating properties, also make BI an exceptional structural candidate for optical chemical sensors. The design of novel benzimidazole-based chemosensors is a challenging task. In this review, molecular sensing systems based on intramolecular charge transfer, photoinduced electron transfer and excited-state intramolecular proton transfer mechanisms are systematically examined and the role of the benzimidazole unit is discussed. Novel and emerging developments such as sensors based on aggregation-induced emission phenomena are also included. Conclusions are made on the advantages and disadvantages of existing fluorophores and chemosensors and guidelines are given for further design and development of new sensing systems based on benzimidazole.

Highly improved Uv resistance and composite interfacial properties of aramid fiber via iron (III) coordination

The poor Uv stability and weak interfacial adhesion are considered as the bottleneck problems for further application of aramid fiber. Herein, a new strategy, Fe3+ coordination, was reported for aramid fiber to simultaneous improve its Uv resistance and composite interfacial shear strength. Fe3+ was introduced onto aramid fiber by coordinating with benzimidazole unit of fiber structure. It can reach a doping capacity of as high as 1516ug/g fiber, and the fiber surface is saturatedly covered with Fe3+. The chemical structure of Fe3+-benzimidazole brings about strong metal-enhanced fluorescence emission effect, which, in turn, greatly raises its Uv stability. Owing to the Fe3+ coordination, the tensile strength of Fe-coordinated fiber could preserve as high as 96% after Uv irradiation, compared with 73% of untreated fiber. Meanwhile, the introduction of Fe3+ improves the surface polarity of aramid fiber and consequently leads to the increase of the composite interfacial shear strength by 39%. It is believed that the Fe-coordinated fiber integrates the advantages of easy production, cost-effective and increased Uv stability, as well as high composite interfacial adhesion, and can be used as promising enhancement for the advanced composite material in harsh environment.

Anion and Guest Directed Tetracyclic Macrocycles of Ag5L4 and Ag6L4 with an Arc-Shaped Ligand Containing Pyridine and Benzimidazole Units: Reversal of Anion Selectivity by Guest

An arc shaped tridentate ligand pyridine-3,5-bis(1-methyl-benzimidazole-2-yl), L, and Ag(I) were shown to form two isomers of Ag5L4 and Ag6L4 templated by ClO4– and CF3SO3– anions, respectively, in DCM-MeOH. Further, the Ag6L4 cluster containing triflate was also found to form in the presence of nitrobenzene, toluene, and p-xylene. Interestingly, the presence of benzonitrile as guest exhibits reversal of anion selectivity that is perchlorate templated Ag6L4 while triflate templated Ag5L4. The guest exchange form the crystalline solid of Ag6L4 resulted in the solid-to-solid transformation to Ag5L4.

Triphenylamine-based fluorescent NLO phores with ICT characteristics: Solvatochromic and theoretical study

The static first and second hyperpolarizability and their related properties were calculated for triphenylamine-based “push-pull” dyes using the B3LYP, CAM-B3LYP and BHHLYP functionals in conjunction with the 6-311+G(d,p) basis set. The electronic coupling for the electron transfer reaction of the dyes were calculated with the generalized Mulliken-Hush method. The results obtained were correlated with the polarizability parameter αCT, first hyperpolarizability parameter βCT, and the solvatochromic descriptor of 〈γ〉 SD obtained by the solvatochromic method. The dyes studied show a high total first order hyperpolarizability (70–238 times) and second order hyperpolarizability (412–778 times) compared to urea. Among the three functionals, the CAM-B3LYP and BHHLYP functionals show hyperpolarizability values closer to experimental values. Experimental absorption and emission wavelengths measured for all the synthesized dyes are in good agreement with those predicted using the time-dependent density functional theory. The theoretical examination on non-linear optical properties was performed on the key parameters of polarizability and hyperpolarizability. A remarkable increase in non-linear optical response is observed on insertion of benzothiazole unit compared to benzimidazole unit.

Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands.

A series of bis-cyclometalated iridium(III) complexes of general formula [Ir(ppy)2(N∧N)][PF6] (ppy- = 2-phenylpyridinate; N∧N = 2-(1H-imidazol-2-yl)pyridine (1), 2-(2-pyridyl)benzimidazole (2), 1-methyl-2-pyridin-2-yl-1H-benzimidazole (3), 2-(4'-thiazolyl)benzimidazole (4), 1-methyl-2-(4'-thiazolyl)benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2][PF6] and [3][PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1][PF6], [4][PF6], and [5][PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photophysical properties are due to the effect that the chemical structure of the ancillary ligand has on the nature of the emitting triplet state. Whereas the benzimidazole unit stabilizes the LUMO and gives rise to a 3MLCT/3LLCT emitting triplet in [2][PF6] and [3][PF6], the presence of the thiazolyl ring produces the opposite effect in [4][PF6] and [5][PF6] and the emitting state has a predominant 3LC character. Complexes with 3MLCT/3LLCT emitting triplets give rise to LEC devices with luminance values 1 order higher than those of complexes with 3LC emitting states. Protecting the imidazole N-H bond with a methyl group, as in complexes [3][PF6] and [5][PF6], shows that the emissive properties become more stable. [3][PF6] leads to outstanding LECs with simultaneously high luminance (904 cd m-2), efficiency (9.15 cd A-1), and stability (lifetime over 2500 h).

Novel Luminescent Benzimidazole-Substituent Tris(2,4,6-trichlorophenyl)methyl Radicals: Photophysics, Stability, and Highly Efficient Red-Orange Electroluminescence

Luminescent radicals have various applications because they simultaneously possess optoelectronic, electronic, and magnetic properties. Despite the development of some luminescent tris(2,4,6-trichlorophenyl)methyl (TTM)-based radicals, all the substituents directly attached to the TTM skeleton are electron-donating groups. Herein, the electron-withdrawing group is first attached to a p carbon of the parent TTM radical, and two novel stable open-shell adducts based on the benzimidazole unit with red-orange emission are obtained. Their photophysical properties, photochemical stabilities, and electroluminescent performances are fully investigated. Because of the introduction of the benzimidazole unit, the intramolecular charge transfer property of D–A type molecules is suppressed to a large extent, and the delocalization of the sole electron is strengthened. Both radicals exhibit largely improved photostability compared to that of the TTM core. High PL quantum yields (ΦF) of 0.39 and 0.36 in doped films are ...

Novel Bipolar Indole-Based Solution-Processed Host Material for Efficient Green and Red Phosphorescent OLEDs.

A new bipolar host material 2-(2'-(5-(dibenzo[b,d]furan-4-yl)-1H-indol-1-yl)-1,1'-biphenyl]-4-yl)-1-phenyl-1H-benzo[d]imidazole (INDY) has been designed and synthesized for solution-processed PHOLEDs. A hole-transporting indole conjugated dibenzofuran scaffold and an electron-transporting benzimidazole unit were orthogonally connected with incorporation of a 2,4'-biphenyl bridge, which endows a balanced bipolar charge transfer distribution and appropriate triplet energy level (>2.6 eV). The twisted conformation of INDY also ensures good thermal/morphological stability with high Tg (148 °C). The solution-processed green PHOLEDs achieved great device efficiencies with 27.33 cd/A and 12.26 lm/W at 7 V. Meanwhile, the red solution-processed PHOLEDs gained excellent performance with the maximum efficiencies of 17.20 cd/A, 9.82 lm/W, and 12.61%. In addition, all of the red devices presented excellent color stability with the same CIE coordinate as (0.65, 0.35) under varying dopant contents and operating voltages.

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.

Synthesis and characterization of porous polyimide films containing benzimidazole moieties

In this study, a series of porous polyimide films containing benzimidazole units were prepared through a phase separation process. The dibutyl phthalate was selected as porogen. The copolyimides were prepared by the reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride with two diamines of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4′-diaminodiphenyl ether with various molar ratios. The resultant porous polyimide films exhibit optimum cell-size distributions. The effects of BIA on morphology, mechanical, and thermal properties of the porous films were explored. It was found that as the BIA content reached up to 30 mol%, the porous copolyimide film demonstrates remarkable thermal stability and admirable mechanical properties with the glass transition temperature of 294°C, 5% weight loss temperature in argon flow up to 545°C, and a tensile strength of 48 MPa. The incorporation of BIA into the polyimide chains brought the highly rigid structures and strong intermolecular interactions, resulting in the enhancement in the thermal stability and the mechanical properties.

Nondestructive grafting of PEI on aramid fiber surface through the coordination of Fe (Ⅲ) to enhance composite interfacial properties

The nondestructive functionalization of aramid fiber is an important research direction. In this study, a kind of benzimidazole-contained aramid fiber, Poly-p-phenylene-benzimidazole-terephthalamide (PBIA) fiber, was modified by the coordination of benzimidazole unit in fiber structure with Fe3+. Further, the coordinatively unsaturated sites of Fe3+ endow the modified fiber with active sites for the grafting of PEI. Model compound of PBIA unit, PBA, was utilized to confirm the whole process of modification. In comparison with that of the untreated fiber, the IFSS value of fiber with PEI grafted has an increase by 47%, owing to the chemical bond formed on the fiber/epoxy interface and the better wettability of resin to fiber. In all, the study presents a nondestructive functionalization of aramid fiber and can be employed in the modification of other benzimidazole-contained substrates.

Polymer electrolyte membrane with heterocyclic terminated poly(ethylene glycol) brushes: An approach to decorate proton conductive species on membrane surface

The incorporation of proton transfer species into the polymer electrolyte membranes (PEM) of the proton exchange membrane fuel cell (PEMFC), in most cases, rely on the chemical modification in solution state before casting the membrane, and therefore, the function of proton transfer species is depending on the membrane physicochemical properties. The present work proposes a simple grafting poly(ethylene glycol) (PEG) onto membrane surface to incorporate PEG hydrophilic chains for the function of water and acid molecules absorption. At the same time, the PEG terminated with benzimidazole provides the proton hopping. Sulfonated poly(ether ether ketone) (SPEEK) is cast to obtain a membrane and its surface is further grafted with polymer brushes of PEG containing benzimidazole terminals. The membrane obtained is stable up to 250°C without degradation indicating the feasibility for high temperature PEMFC. The proton transfer is under the vehicle mechanism in non-humidified condition where the conductivity and water uptake of the membranes are increased when increasing of PEG chain length in combination with the benzimidazole units. The direct surface modification of PEM with polymer brushes is a simple way to enrich the surface with proton transfer species and gaining membrane stability without the problems of phase separation.

Alternating α-Olefin Distributions via Single and Double Insertions in Chromium-Catalyzed Ethylene Oligomerization

The catalytic oligomerization of ethylene with chromium-based complexes containing bis(benzimidazolemethyl)amine (BIMA) ligands results in alternating distributions of linear α-olefins (LAOs). Extremely high activities are obtained (>100 000 g mmol–1 h–1 bar–1) with N-alkyl-substituted BIMA ligands, whereas bulky groups on the central nitrogen or alternative central donors result in much lower activities. Variations in the ligand backbone, as well as methylation of the benzimidazole units, lead to reduction in activity. The alternating LAO distributions have been mathematically analyzed using second-order recurrence relations. The shape of the distributions is affected by ethylene pressure (1–4 bar) and by the cocatalyst to some degree. On the basis of the results and analysis presented herein, we propose that the alternating behavior originates from the ability of these chromium BIMA catalysts to undergo single as well as double ethylene insertion reactions. A minor second distribution (<5 wt %) of 2-eth...

Novel Thiazole Based Styryl Dyes with Benzimidazole Unit - Synthesis, Photophysical and TD-DFT Studies.

Three new Y-shaped styryl dyes were designed and synthesized from thiazole carbaldehyde with different active methylene compounds as acceptor moieties. All the dyes were characterized by IR, 1HNMR, MS/LCMS/HRMS. Spectroscopic properties and non-linear optical properties styryl derivatives were analyzed and the effect of change in solvent polarity on their absorption and emissive properties has been investigated. The dye with (1-phenylethylidene) propanedinitrile unit shows red shift absorption/emission profile among all the dyes. Density Functional Theory and Time Dependent-Density Functional Theory computations have been used for comparative study with the experimental data and also to understand the structural, molecular, electronic and photophysical parameters of the styryl dyes. The computational method was also employed to investigate the nonlinear optical properties of the styryl dyes in different organic solvent. The unsubstituted benzimidazolyl thiazole styryl dyes possess good non-linear optical properties.