Ortho-phenylenediamine Research Articles

Synthesis, crystal structure and self-assembly of novel ninhydrin-derived isoquinoline compounds

Isoquinoline skeletons are ubiquitous in natural products and pharmaceuticals with broad range of biological activity. In the present work, novel isoquinoline compounds are synthesized via the insertion of suitable nucleophile into the ninhydrin core. The reaction of ninhydrin with acetamide in refluxing AcOH afforded indanedione linked isoquinoline derivative 1. On the other hand, treatment of ninhydrin-4-methoxyphenol adduct 2 with ortho phenylenediamine in EtOH/AcOH led to the formation of isoquinoline fused benzimidazole scaffold 3. In DMSO‑d6 medium, compound 3 get oxidized to the corresponding isoquinolinone form 4. Single crystal X-ray diffraction study revealed that isoquinoline derivative 1 self-assembled to form zipper arrangement. Interestingly, fused isoquinoline scaffold 4 was found to display supramolecular helical arrangement in the crystalline state. The role of weak intermolecular interactions for development of supramolecular structure has been analysed and quatified using Hirshfeld surface analysis. The scanning electron microscopy (SEM) images of compound 1 show the formation of vesicular structure, whereas structurally analogous compounds 3 and 4 exhibit fibrilllar morphology.

Physical structure, TD-DFT computations, and optical properties of hybrid nanocomposite thin film as optoelectronic devices

HCl doped-copolymer of ortho phenylene diamine and meta phenylene diamine was prepared by using oxidative polymerization method with ferric chloride as an oxidizing agent in the existence of sodium dedocyl sulphate as a soft template. The microporous structure thin films of hybrid copolymer/ZrO2 nanocomposite [copolymer/ZrO2]NC were fabricated using a physical vapor deposition (PVD) method. The effect of addition of zirconium oxide nanoparticles [ZrO2]NPs on the physical properties of the copolymer was discussed in the light of crystallinity and optical properties. The average crystallite size of [ZrO2]NPs is around 40 nm. The copolymer showed an absorbance of 1.18 at the wavelength (λ) 374 nm, which increased to 1.26 at λ = 440 nm after glycine addition, also increased to 1.53 at λ = 486 nm after [ZrO2]NPs loading. Also, the significant changes in the absorption index and indirect/direct bandgap of the copolymer have been detected. The materials Studio 7.0 program on TDDFT/DMol3 was used to optimize the molecular structure and perform the frequency calculations for the crystal models and isolated molecules. The DFT-Gaussian09W-vibration values are quite similar to the experimental data either in the structure or in the optical properties. The improvements in optical properties were achieved and revealed the possibility of using the hybrid nanocomposite films in the polymers solar cell application.

Synthesis and Spectral Characterization of Novel Schiff Base and Fe(II) Complex: Evaluation of Antibacterial, Antifungal, and Anticancer Properties

Schiff’s bases are a type of molecule found in medical chemistry that has been shown to have substantial antibacterial and chemotherapeutic properties. On the other hand, Ortho phenylenediamine is a broad category of synthetic chemical with various pharmacological properties, including anticancer potential. Their antibacterial, antifungal, and anticancer properties, in particular, make the compounds appealing for future derivatization and screening as potential therapeutic agents. Accordingly, this study aimed to synthesize a novel Schiff’s base-Fe(II) complex using the self-assembly method for in-vitro studies due to its potential drug properties for therapeutic intervention in various diseases. The as-synthesized Fe(II) complex was characterized by spectral and elemental techniques. The obtained data from the elemental analysis was in good agreement with the general formula MLCln (L= Ligand complexed with Fe(II) via carbonyl group, the nitrogen of hydrazine group, and oxygen). Additionally, Fe(II) complexes with Schiff’s bases were shown to have gastro-protective, antiproliferative, and antibacterial properties. The Schiff’s base and its Fe(II) complex were screened against gram-positive (B.subtilies), gram-negative (E.coli) as well as A.niger to evaluate the antibacterial and antifungal properties, respectively. The obtained results demonstrated that the Schiff’s base –Fe(II) complex has higher antibacterial and antifungal activity than Schiff’s base ligand. Furthermore, cytotoxicity studies were performed for Schiff base and its Fe(II) complex against breast cancer (MCF-7) cell lines. The findings of this study recommended new insights in the field of medicine to consider Schiff’s base-Fe(II) complex as a potential candidate for the antibacterial, antifungal, and anticancer agent.

An efficient photocatalytic synthesis of benzimidazole over cobalt-loaded TiO2 catalysts under solar light irradiation

Cobalt-loaded TiO2 (Co-TiO2) based photocatalysts have been successfully used in energy and environmental applications, but their application in synthesis of Benzimidazole from ortho phenylenediamines has never been reported. Benzimidazole is a very important class of heterocyclic compounds and it occupies a unique position in the field of pharmaceutical chemistry. Here, Co-TiO2 photocatalysts were prepared using an impregnation method and characterized by XRD, UV–Vis DRS, FE-SEM, TEM and Raman techniques. The present study explores the photocatalytic synthesis of 2-Aryl Benzimidazoles over cobalt-loaded TiO2 under solar light irradiation. The cobalt-loaded TiO2 catalysts exhibited excellent photocatalytic performance under solar light in the preparation of 2-Aryl Benzimidazoles. This efficient and higher photocatalytic activity can be attributed to the visible light active structure of Co-TiO2 and surface-interacted cobalt species on TiO2 support.

Synthesis and Biological Evaluation of Some Newer 1h-Benzo[b][1,5]diazepin-2(3h)-One Derivatives as Potential Anticonvulsant Agents

Background: Regardless of the availability of all novel and earlier treatments, seizure control is notoriously complicated. In the hopes of discovering the latest and ultimate therapy, medicinal chemists will keep on to hunt for new antiepileptic compounds with high specificity and low CNS toxicity. The biological effects of benzodiazepine compounds have been examined. Benzene and a diazepine ring are fused together to form the chemical structure. Diverse combinations of moieties attached to the innermost structure in positions 1, 2, 5, and 7 the pharmacological qualities, effect potency, and pharmacokinetic conditions are all influenced by the various side groups. Method: This paper describes the synthesis of several 1H-benzo[b][1,5]diazepin-2(3H)-one derivatives. The substituents at N1 are benzoyl, 5-substituted-1,3,4-thiadiazoles-2-yl-aminoacetyl. Condensation of orthophenylene diamine with ethyl acetoacetate gave 7-substituted-4-methyl-1H-benzo[b][1,5]diazepin-2(3H)-ones, which were then linked to benzoyl chloride and chloroacetyl chloride to yield N1-benzoyl and N1-chloroacetyl derivatives. N1- chloroacetyl derivatives were further linked with 5-substituted-1,3,4-thiadiazoles amines using microwave irradiation. Result: IR, 1H-NMR, and mass spectroscopy were used to authenticate the synthesized compounds. The PTZ produced convulsions method was used to test the compounds for anticonvulsant activity. Compounds 4a and 4c gave 80% protection at 0.4 mg/kg, whereas Compounds 2a and 2c offered 80% protection at 20 and 30 mg/kg, respectively, when compared to the Control. Conclusion: When compared to a control, the experimental synthesis and pharmacological assessment of the 1,5-benzodiazepin-2-one moiety replaced with 1,3,4-thiadiazole yields a potentially active anticonvulsant drug.

Synthesis and characterization of some 1, 5-benzodiazepine derivatives from Chalcones and their use as scavengers for some heavy metals in Environmental Systems.

Chalcones (A1-A4) compounds were prepared by reacting an aldehyde (Cinnamaldehyde or terphthaldehyde) with a ketone (4-aminoacetophenone or acetylacetone) in the presence of 30% NaOH as a catalyst and ethanol as a solvent. Derivatives of 1,5-benzodiazepine (A5-A12) were prepared by reacting these prepared chalcones with orthophenylene diamine or 4-methylorthophenylene diamine in a basic medium of sodium hydroxide 10% using the microwave method. Some prepared compounds were used as scavengers of some heavy metals (iron and lead) from heavy water in ecosystems, as the results indicated the ability of these compounds to reduce or withdraw these elements from heavy water. The stability of these compounds was also tested against laser rays, as they showed resistance and stability towards laser rays.

Determination of Potential Genotoxic Impurities (Orthophenylene Diamine Dihydrochloride), 4'-Bromomethyl-2-Cyanobiphenyl, 4'(Dibromomethyl)[1,1'-Biphenyl]-2-Carbonitrile in Telmisartan by ESI-MS/MS.

A sensitive, simple, rapid and robust LC-MS/MS method was developed for the determination of potential genotoxic impurities OPDA HCl (orthophenylene diamine dihydrochloride), bromo OTBN (4'-bromomethyl-2-cyanobiphenyl), dibromo (4'(dibromomethyl)[1,1'-biphenyl]-2-carbonitrile) in Telmisartan by using ESI-MS/MS Technic; the study was performed with gradient elution (time/% mobile phase B: 0/10, 3/10, 30/80, 35/80, 36/10, 40/10). The mobile phase consisted of a mixture of formic acid, methanol and acetonitrile. The buffer was degassed before running at a flow rate of 1.0mL/min. The column temperature was at 40°C. The 20μL volume of sample was injected per run and peaks were detected using DAD detector. The LC-ESI/MS/MS studies were carried out on Ultivo Triple Quadrupole LC/MS/MS (Agilent, USA) G6470A mass spectrometer, ion source voltage 3500V, de clustering potential 40V, entrance potential 10V, with the nebulizer gas as nitrogen at 45psi. The LC part consisted of Agilent 1260 series HPLC system with binary gradient pump with a degasser and an auto sampler. Inert sustain AQ-C18, 250 × 4.6mm, 5-μm particle size was used for chromatographic separation. Developed method is validated as per ICH guidelines and found to be linear, accurate, specific, selective, precise and robust. Test solution was found to be stable up to 48h. This method can be successfully applied for the determination of genotoxic impurities in Telmisarta for routine analysis and stability assessment.

Microwave assisted synthesis of poly(ortho-phenylenediamine-co-aniline) and functionalised carbon nanotube nanocomposites for fabric-based supercapacitors

A copolymer of ortho phenylenediamine and aniline was synthesised by a microwave assisted technique. Acid functionalised carbon nanotubes were incorporated into the polymer matrix. The copolymer and the nanocomposite were extensively characterised using spectral, morphological and thermal analysis techniques. Fabric-based supercapacitor devices were fabricated using these materials and their electrochemical properties were analyzed. Both the copolymer and the nanocomposite exhibited a high specific capacitance of 147.14 F g−1 at 0.50 A g−1 with a capacitance retention of 82%. A low relaxation time constant of 4.5 ms was observed for the fabricated device using the nanocomposite. The copolymer and the nanocomposite were also subjected to in vitro cytotoxicity studies and they showed high biocompatibility. Due to their enhanced electrochemical performance coupled with biocompatibility, these materials can be expected to exhibit great promise as an alternative to traditional supercapacitors.

Influence of substituent position in aromatic diamines on coumarin derivative

The Influence of substituent position in aromatic diamines such as ortho-phenylenediamine (OPD) and para-phenylenediamine (PPD) on 7-methoxy-4-azido methyl coumarin (7MCA) has been studied in different solvents. A hypsochromic shift in the absorption maximum of 7MCA in the presence of aromatic diamine indicates the formation of the complex. From the 1H NMR study, it is understood that there is an H-bonding between the NH2 proton of OPD and 7MCA. A shift in the N–H stretching band of OPD observed in FT-IR spectra towards lower frequency indicates H-bonding between 7MCA and OPD. But the nature of the interaction between PPD and 7MCA cannot be determined from NMR and FT-IR study. Non-linear S-V plots obtained from the fluorescence quenching study reveals the involvement of both static and dynamic quenching processes. The value of the quenching rate parameter for para-phenylenediamine is more than ortho-phenylenediamine in protic solvents. But the value of the quenching rate parameter for ortho-phenylenediamine is more than its para isomer in aprotic solvents. Electrochemical analysis reveals that there is no electron transfer from these amino anilines to coumarin derivatives. The Nature of force between 7MCA and aromatic diamine (OPD and PPD) is hydrophobic in methanol since the change in enthalpy and entropy are positive but these thermodynamic parameters have negative values in DMF solvent indicating, a weak van der Waals force between 7MCA and amino anilines.

Facile and green preparation of colorimetric and fluorescent sensors for mercury, silver, and carbonate ions visual detecting: Spectroscopy and theoretical studies

Two new fluorescent and colorimetric chemosensors based on benzimidazole derivatives (A, B) have been successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA) and two different aldehydes in the presence of SBA-Pr-SO3H. These chemosensors used to the successive detection of Hg2+, Ag+, and CO32− ions. The stoichiometric ratio of sensors toward Ag+/CO32− ions for in the case of A was 2:1 and of Hg2+ B was 1:1. Both A and B probes have shown rapid and short response times (1 min). Furthermore, the optimized structures, binding mechanisms, and electronic transitions were supported with a high correlation and agreement by spectroscopy, DFT and NCI calculations

Simple RuCl3‐catalyzed N‐Methylation of Amines and Transfer Hydrogenation of Nitroarenes using Methanol

AbstractMethanol is a potential hydrogen source and C1 synthon, which finds interesting applications in both chemical synthesis and energy technologies. The effective utilization of this simple alcohol in organic synthesis is of central importance and attracts scientific interest. Herein, we report a clean and cost‐competitive method with the use of methanol as both C1 synthon and H2 source for selective N‐methylation of amines by employing relatively cheap RuCl3.xH2O as a ligand‐free catalyst. This readily available catalyst tolerates various amines comprising electron‐deficient and electron‐donating groups and allows them to transform into corresponding N‐methylated products in moderate to excellent yields. In addition, few marketed pharmaceutical agents (e. g., venlafaxine and imipramine) were also successfully synthesized via late‐stage functionalization from readily available feedstock chemicals, highlighting synthetic value of this advanced N‐methylation reaction. Using this platform, we also attempted tandem reactions with selected nitroarenes to convert them into corresponding N‐methylated amines using MeOH under H2‐free conditions including transfer hydrogenation of nitroarenes‐to‐anilines and prepared drug molecules (e. g., benzocaine and butamben) as well as key pharmaceutical intermediates. We further enable one‐shot selective and green syntheses of 1‐methylbenzimidazole using ortho‐phenylenediamine (OPDA) and methanol as coupling partners.

Combined experimental and TDDFT computations for the structural and optical properties for poly (ortho phenylene diamine) thin film with different surfactants

Poly(ortho-phenylenediamine) micro-rods (PoPD) are synthesized in the acidic medium at 25 °C by an oxidative polymerization method in the absence or the presence of a soft template including the following surfactants para toluene sulfonic acid (PoPD-PTS) and trisodium citrate (PoPD-TSC). Then, the thin films of poly(ortho-phenylenediamine) (PoPD)F, toluene sulfonic acid (PoPD-PTS)F, and trisodium citrate (PoPD-TSC)F are fabricated using the physical vapor deposition method (PVD). The fabricated thin films are characterized by several techniques includes Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), UV–Vis spectroscopy (UV–Vis), scanning electron microscopy (SEM), and optical properties are interpreted in-depth. The optimization for the samples is carried out by applying density functional theory (DFT) with DMol3 and Cambridge Serial Total Energy Package (CASTEP) program. XRD measurements of thin film showed a crystal structure of monoclinic 2, and there is an increase of polymer crystallite size when used PTS and TSC surfactants in the preparation of the polymer. The study of surface morphology shows a smooth surface with uniform micro-rods for the resulting polymer. The optical constants including refractive index (n), absorption index (k) are calculated. Based on the optical measurements, the optical constants decrease with increasing photon energy while optical conductivity, and dielectric constants increase. Following the experimental analysis, the optical properties of simulated FT-IR, XRD, and CATSTEP are in good agreement with the experimental ones. (PoPD-PTS)F and (PoPD-TSC)F films are a good applicant for optoelectronics and solar cells.

Design, Synthesis of Analgesics and Anticancer of Some New Derivatives of Benzimidazole

This work, contains some new compounds from benzimidazole derivatives, which are synthesized by condensation of Orthophenylene diamine and Carbon disulfide resulting in 2-Mercapto-benzimidazole which is treated by alcoholic potassium hydroxide forming potassium salt of 2-mercaptobenzimidazole which reacts with different substances (alkyl chloroacetates, chloroacetic chloride, alkyl halides) also the ethoxy carbonyl methyl thiobenzimidazole reacts with different amines. In addition to chloromethyl benzimidazole which resulted from the reaction between orthophenylene diamine and chloroacetic acid, which reacted with different amines. The synthesized compound tested as analgesics and anticancer activity the new derivatives revealed moderate, strong and very strong analgesics and moderate and strong anticancer activity.

Acenaphtoquinoxaline as a selective fluorescent sensor for Hg (II) detection: experimental and theoretical studies

A new fluorescent chemosensor based on quinoxaline was successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA) and acenaphthylene-1,2-dione in the presence of SBA-Pr-SO3H. Prepared a “switch-off” quinoxaline-based receptor to recognized Hg2+ ion in high selectively and, without any interference from other metal ions, was developed. The photophysical behavior of this fluorophore was studied in acetonitrile by using fluorescence spectra. The fluorescence properties of several cations to acenaphtoquinoxaline were investigated in acetonitrile, and the competition test displayed that the probe fluorescence changes were specific for Hg2+ ion. The obtained results have shown high selectivity and sensitivity only for Hg2+. Also, the detection limit was as low as 42 ppb, and a top linear trend was observed between the concentration of Hg2+ ions and fluorescence intensity. The binding stoichiometry between chemosensor L and Hg2+ was found to be 1:1. Moreover, a computational study was performed to obtain an electronic description of the fluorescence emission and quenching mechanisms. The optimized structures and binding mechanisms were supported with a high correlation and agreement by spectroscopy and DFT calculations.

Design, Synthesis and Biological Evaluation of 2-Aminobenzimidazole Derivatives as DPP4 Inhibitors

Background: The objective of the research was to examine the DPPIV inhibitor activity of synthetic derivatives of 2-aminobenzimidazole derivatives by the in-vivo method. Methods: Molecular docking was performed using homology model of receptors to identify the binding sites for the inhibitory activity of diabetes by means of- CDocker energy using the Discovery Studio (DS) 4.5 Novel 2-amino benzimidazole derivatives were synthesized from orthophenylene diamine with cyanogens bromide. The synthesized compounds were identified by IR,1HNMR,13CNMR, and MASS spectroscopic techniques. The products were analyzed for their DPPIV inhibitory effects on Wistar Albino rat. Results: The results revealed that benzimidazole with para-aminobenzoic acid possesses best DPPIV inhibitor activity. 2- amino benzimidazole incorporated with aromatic compounds were synthesized and assessed for their DPP-IV inhibitor activity. Conclusion: 2- amino benzimidazole with para-aminobenzoic acid can be used as a lead compound for the development of a new class of DPP-IV inhibitor.

Improvement of the thermal stability and optical properties for poly (ortho phenylene diamine) using soft templates

A crystalline protonated-poly (ortho phenylenediamine) microrods [POPDA] with ladder-type structure was elaborated at room temperature in an acidic medium. The synthesis method was based on an oxidative polymerization, including sodium dodecyl sulphate [POPDA-SDS] and glycine [POPDA-Gly]. In case of absence or soft template presence, thin films from the considered polymers were fabricated by physical vapor deposition (PVD). Both the resulting polymer flakes and prepared thin films were studied via different techniques such as XRD, FTIR, TGA, SEM, UV–Vis, while optical properties are discussed in detail. The optimization of the samples was performed using Cambridge Serial Total Energy Package (CASTEP) program and density functional theory (DFT) by DMol3. Structural properties of resulting polymers were determined by XRD and FT-IR analysis. XRD results of thin films showed (Monoclinic 2) crystal structure and showed an increase in crystallite size for the polymer, prepared in the presence of SDS surfactants. The surface morphology study revealed the existence of a smooth surface with a significant number of uniform microrods. The optical calculation showed that absorption index k, refractive index n, dielectric constants, and optical conductivity decrease with photon energy increase. The optical properties of simulated FTIR, XRD, and CATSTEP of the considered polymers present a respectable level of experimental study agreement. The polymer thin films present a promising case to be the right candidate for optoelectronics and solar cell applications.

Computational design of molecularly imprinted polymer for electrochemical sensing and stability indicating study of sofosbuvir

In this work, a biomimetic electrochemical sensor for sofosbuvir (SOFO) was designed and optimized for its determination in pure forms, pharmaceutical formulations, urine besides forced degradation products. Computational calculations, based on density functional theory (DFT) at the B3LYP/6-31G(d) level, were initially employed to screen some of the commonly used electropolymerizable functional monomers including para-aminothiophenol (PTP), ortho-aminophenol (OAP), ortho-phenylenediamine (OPD), and pyrrole (PY). Based on the computational calculations, the imprinted sensor active sites were engineered via electropolymerization of OAP, which was found to show the highest binding efficiency to the target drug, on a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (f-MWCNTs) and reduced graphene oxide (RGO) nanocomposite for sensitive determination of SOFO. The fabrication variables of the sensor such as accumulation time, (f-MWCNTs&RGO) loading amount, number of electropolymerization cycles, variation of (template: monomer) ratio, pH, extraction solvent, and binding and rebinding conditions were optimized. The proposed electrchemical sensor was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). Differential pulse voltammetry (DPV) was employed for obtaining the calibration curve and optimization of significant factors that control the sensor performance. To prepare the sensor, 2.5 µL of (f-MWCNTs&GO) were first casted on GCE where GO was reduced electrochemically to RGO followed by 20 electropolymerization cycles of a mixture that is (1:11) SOFO: OAP then a mixture of methanol and 0.5 M H2SO4 (4:1 V/V) can be used for template removal after almost 1 min of incubation with the sensor, while 5 min were enough for rebinding with SOFO once more at pH 7. The proposed sensor exhibited a linear range of (0.53–74.13) ng/mL and significant detection limit at 0.05 ng/mL (S/N = 3) using DPV in addition to good reproducibility and selectivity. Finally, the imprinted sensor was successfully applied for the analysis of SOFO in pure samples, urine, two different pharmaceutical formulations, and electrochemical stability indicating study.

CHARACTERIZATION AND ANTIMICROBIAL EVALUATION OF SUBSTITUTED BENZIMIDAZOLE DERIVATIVES

A blend of 32.4 g (0.1 mole) of ortho phenylenediamine (OPD), 19.5g (0.1 mol) of Potassium hydroxide (KOH) and 26 g (0.1 mole) of carbon disulphide (CS2), 300 ml of 95% ethanol and water were taken in round base flagon and reflux give coupling prouct benzimidazole 2-thiol (1) was isolated as flicker white precious stone. 10.75ml of concentrated nitric corrosive and equivalent amount of concentrated sulphuric corrosive (1:1) was included The nitration item 5-nitro benzimidazole 2-thiol (2) was shaped as yellowish pale shading, at that point S-alkylated subordinates framed from 5-Niro benzimidazole 2-thiol utilizing acetonitrile (20 ml) containing 2 ml (14 mmol) DBU followed by the expansion of 0.72 g (5 mmol) of 2-diethylaminoethylchloride (3i), 4-aminobenzylchloride (3ii), 4-Hydroxybenzylchloride (3iii), 4-nitro 2-Hydroxybenzylchloride (3iv) give The arrangement was mixed for the time being at room temperature and the dissolvable vanished. Water (5 ml) was added to the buildup and the blend was carried to pH 7 with CH3COOH. The accelerate framed was sifted and solidified from H2O to give last item (3a), (3b), (3c), (3d) individually.
 Keywords: Benzimidazole, Anti-microbial, S-Alkylation benzimidazole, 2- mercapto benzimidazole.

Adsorptive interaction of ortho-phenylenediamine with commercial activated carbon in presence of Indole and vice versa: synergistic/antagonistic evaluation

Ortho-phenylenediamine (OPD) and Indole are nitrogenous organic compounds. Ortho-phenylenediamine has been reported to be an endocrine disrupting chemical and is genotoxic in nature, whereas, Indole is mutagenic and carcinogenic. OPD and Indole both all together are present in effluents of several industries, and their simultaneous (binary in the present study) adsorption equilibrium data are required in designing the adsorption system/reactor for separation. Therefore, in the present work, simultaneous adsorption study for adsorption of OPD and Indole from their binary solution, on to low cost commercial grade activated carbon was conducted. Adsorption experiments were performed at 288–318 K, and simultaneous equilibrium adsorption data (binary data in the present study) were collected. Further, various multicomponent competitive isotherms [Langmuir (extended), Freundlich (extended), Sheindorf–Rebuhn–Sheintuch and competitive Redlich–Peterson (modified)] were used to validate the experimental equilibrium isotherm data, and parameters of various isotherms were calculated. Moreover, synergistic/antagonistic effects were also evaluated. Freundlich (extended) and Sheindorf–Rebuhn–Sheintuch isotherm models best represented the experimental data.

1,2-Disubstituted Benzimidazoles by the Iron Catalyzed Cross-Dehydrogenative Coupling of Isomeric o-Phenylenediamine Substrates.

Benzimidazoles are common in nature, medicines, and materials. Numerous strategies for preparing 2-arylbenzimidazoles exist. In this work, 1,2-disubstituted benzimidazoles were prepared from various mono- and disubstituted ortho-phenylenediamines (OPD) by iron-catalyzed oxidative coupling. Specifically, O2 and FeCl3·6H2O catalyzed the cross-dehydrogenative coupling and aromatization of diarylmethyl and dialkyl benzimidazole precursors. N,N'-Disubstituted-OPD substrates were significantly more reactive than their N,N-disubstituted isomers, which appears to be relative to their propensity for complexation and charge transfer with Fe3+. The reaction also converted N-monosubstituted OPD substrates to 2-substituted benzimidazoles; however, electron-poor substrates produce 1,2-disubstituted benzimidazoles by intermolecular imino-transfer. Kinetic, reagent, and spectroscopic (UV-vis and EPR) studies suggest a mechanism involving metal-substrate complexation, charge transfer, and aerobic turnover, involving high-valent Fe(IV) intermediates. Overall, comparative strategies for the relatively sustainable and efficient synthesis of 1,2-disubstituted benzimidazoles are demonstrated.