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Although peroxidase-like nanozymes have made great progress in bioanalysis, few current nanozyme-based biosensors are constructed for discriminating isomers of organic compounds. Herein, fluorescent metal-organic framework (MOF)-based nanozyme is utilized for phenylenediamine isomers discrimination and detection. NH2-MIL-101(Fe), as a member of Fe-based MOFs, functions as not only fluorescent indicator but also peroxidase mimics. In the presence of H2O2, NH2-MIL-101(Fe) can catalyze the oxidation of o-phenylenediamine (OPD) and p-phenylenediamine (PPD) into their corresponding oxidation products (OPDox and PPDox), which in turn quench its intrinsic fluorescence at 445 nm via inner filter effect (IFE). Differently, a new fluorescence peak at 574 nm is observed for OPDox. Thus, a ratiometric fluorescence method for the detection of OPD can be designed with the fluorescence intensity ratio F574/F445 as readout. This proposed strategy displays excellent discrimination ability for three phenylenediamines and may open new applications of MOFs in environmental science.

Ratiometric fluorescence immunoassay is known as a spectrofluorimetric variant for sensitive and quantitative analyses of biomarkers. However, there are few comparative studies between it and the traditional, single-wavelength-based immunoassay. In this work, a ratiometric fluorescence immunoassay was designed via the fluorescence resonance energy transfer (FRET) in a system comprising MnO2 nanosheets, o-phenylenediamine (OPD), and fluorescent carbon nanodots (FCNs). The MnO2 nanosheet oxidizes OPD, producing a fluorescence peak at 580 nm, while FCNs exhibit a fluorescence peak at 490 nm. Under the effect of FRET, the fluorescence at 580 nm increases significantly while the fluorescence at 490 nm is reduced. The FRET effect was confirmed by our fluorescence lifetime measurements. We optimized the experimental conditions that include solution pH, OPD concentration, and reaction time. By electrostatically coating the MnO2 nanosheets with antibody molecules and using the resultant materials as a detection probe, the ratiometric fluorescence sensing was extended to the detection of alpha fetoprotein (AFP) in human serum samples on a 96-well titer plate. Our ratiometric fluorescence immunoassay possesses a good dynamic range (from 0.14 to 130.43 pM). The detection limit was estimated to be 0.13 pM (0.009 ng/mL), which is 7.6-fold lower than that of the single-wavelength-based immunoassay. The measurement results of serum samples from healthy and patient donors are highly comparable to those measured by chemiluminescence for the same donors, demonstrating the viability for serological assays of important cancer markers.

α-Dicarbonyls (α-DCs) are key reactive Maillard intermediates with structural diversity and are widely found in foods and in vivo, but little is known regarding the complete molecular profiles of these potentially harmful electrophiles. Herein, we reported a novel isotope-coding derivatization (ICD) strategy for the broad-spectrum, quantitative profiling of (non)target α-DC species in natural foodstuffs. It utilized differential isotope labeling (DIOL) with a reagent pair o-phenylenediamine (OPD)/OPD-d4 (deuterated) to form stable quinoxalines for class-specific fragmentation-dependent acquisition using liquid chromatography-hybrid quadrupole linear ion trap mass spectrometry (LC-QqLIT). A combination of facile one-pot quantitative labeling and convenient cleanup protocol afforded satisfactory sensitivity, linearity, accuracy (81-116%), and process recovery (86-109% with RSDs < 10%) by matrix-matched ICD-internal standard calibration, without significant matrix interference (-9 to 5%), isotopic effect (

This article proposes a fluorescence and ultraviolet colorimetric determination of formaldehyde (HCHO) in solution based on the autocatalytic oxidation reaction of O-phenylenediamine (OPD) induced by silver ions (Ag+). Due to the substantial oxidizing properties of Ag+, OPD can be catalyzed to produce silver nanoparticles (AgNPs) and yellow 2,3-diaminophenazine (OPDox) by Ag+, and OPDox has yellow fluorescence under the irradiation of portable ultraviolet lamps. There are fluorescence and ultraviolet absorption peaks at 562 nm (Fluorescence spectrophotometer) and 445 nm (UV spectrophotometer), respectively. In the presence of formaldehyde (HCHO), HCHO may induce Ag+ aggregation and inhibit the oxidation ability of Ag+. Also, HCHO has notable reducing properties and can reduce OPDox to OPD, which reduces the concentration of OPDox, causing the detection solution to fade to pale yellow or even colorless and reduce fluorescence and UV absorption intensity. Therefore, the proposed HCHO detection method based on the Ag+–OPD sensor system had a wide linear range of 0.01 ~ 10000 μg/L. In the buffer, the detection limits were 0.02 μg/L (fluorometric method) and 0.06 μg/L (Ultraviolet measurement method). In the simulated tap water samples, the detection limits were 0.05 μg/L (fluorescence measurement) and 0.09 μg/L (UV measurement), and in the lake water simulation samples, the detection limits were 0.10 μg/L (fluorescence measurement) and 0.17 μg/L (UV measurement). The method we presented can detect HCHO in solution, and the entire experimental process did not exceed 30 min. It has high sensitivity and low detection limit, and may be used for the detection of HCHO in other actual samples.

The monitoring of deferasirox (DEF) has important clinical roles in patients who need iron excretion. However, analytical methods with practicability and simplicity are limited. Moreover, ratiometric fluorescence strategies based on Forster resonance energy transfer (FRET) from carbon dots (CDs) as a donor are rarely reported as a drug monitor. In this work, CDs with an appropriate emitting wavelength at 480 nm and excitation around 370 nm were prepared by hydrothermal approach and HCl post-treatment. O-Phenylenediamine (OPD) can be oxidized by Cu2+ to produce yellow fluorescent 2,3-diaminophenazine (oxOPD) in the system of Cu2+ and OPD (Cu–OPD). Correspondingly, a remarkable FRET from CDs to oxOPD in the system of CDs, Cu2+ and OPD (CDs–Cu–OPD) was fabricated with the quenching illustration of CDs, but emitting property of oxOPD. Attributed to the chelation ability of DEF on Cu2+, the inhibitory effects of DEF on the Cu2+-triggered oxidative capability reduced the FRET system by the decreased oxOPD. Thus, the recovered CDs at F480 and decreased oxOPD at F560 were found through a ratiometric mode by the addition of DEF in CDs–Cu–OPD for the DEF assay. The FRET behavior of CDs and oxOPD in CDs–Cu–OPD was proved clearly through the calculation of the association constant, binding constant, number of binding sites, and the distance between the donor and acceptor. Furthermore, this ratiometric method exhibited promising analytical performance for DEF with the application in real samples. The implementation of this work expands the application field of CDs and OPD oxidation in drug monitoring, and even other biological analyses through ratiometric strategy.

Carbon dots (CDs), as the most important type of carbon-based material, have been widely used in many fields because of their excellent properties. In particular, multicolor fluorescent CDs with high photoluminescence quantum yield are the focus of active research. Herein, red, green and blue CDs (RGB CDs) were successfully synthesized by a solvothermal method from o-phenylenediamine under different reaction conditions. The RGB-CDs have stable optical properties and significant photoluminescence characteristics. Structural and elemental analyses propose a conjugated structure and the surface state of the CDs as the main causes for the different color emission of RGB-CDs. In addition, a white fluorescent CD solution was prepared by mixing these multicolor fluorescent CDs in appropriate proportions.

A label-free, rapid, and highly sensitive colorimetric assay for the detection of glutathione (GSH) was developed. o-Phenylenediamine (OPD) can be selectively oxidized by Au3+ in phosphate buffer to produce light yellow 2,3-diaminophenazine. After the addition of GSH, the autocatalytic redox reaction between OPD and Au3+ can be effectively inhibited, resulting in a significant decrease in chroma and absorbance intensity. Reduced absorbance intensity can be used for the quantification of GSH. In addition, this method can achieve the discriminative detection of biothiols, such as cysteine and homocysteine. Based on these findings, a simple colorimetric assay was developed for the detection of GSH in the range of 1 nM to 1 mM with a low detection limit of 0.08 nM. More importantly, this procedure is simple, and the whole assay can be accomplished quickly within 15 min. Additionally, the proposed method was successfully used for the determination of GSH in biological fluids, such as serum samples.

A series of quinoxaline derivatives were efficiently synthesized by convenient and simple procedure in excellent yields using 1 wt.% of titanium silicate (TS-1) catalyzed reaction of 1,2-diamines and 1,2-diketones in methanol at room temperature. This reaction is scalable to multigram scale and the catalyst is recyclable.

We report a fluorescence assay for alkaline phosphatase (ALP) detection using in situ generation of 2,3-diaminophenazine (OPDox) through an inner filter effect (IFE). AgNO3 can oxidize o-phenylened...

o-Phenylenediamine (OPD) can be readily oxidized by several types of oxidants to generate fluorescent 2,3-diaminophenazine (oxidized OPD, OPDox). The unique fluorescence response process during the oxidation of OPD provides an important model for the design of novel sensors. In recent years, a series of fluorescent and colorimetric sensors have been developed based on the oxidation of OPD. In this review, fluorescent and colorimetric sensors for the detection of metal ions and small organic molecules are discussed. These sensing processes exhibit distinguishable and prominent fluorescent and colorimetric responses. The sensing systems include autocatalytic reactions and using nanomaterials, carbon dots, or fluorophore labeled DNA as reference fluorophore for fluorescent and colorimetric detection.

o-Phenylenediamine as a new fluorescent probe is designed for detecting Ce(IV) ions. The mechanism of detection relies on the oxidative activity of Ce(IV) ions, which can promote the oxidative cyclization of o-Phenylenediamine leading to the formation of fluorescent 2,3-diaminophenazine and giving a more than 150-fold fluorescence enhancement. Furthermore, the o-Phenylenediamine fluorescent probe was effectively used for the detection of Ce(IV) ions in river water, tap water, rainwater, and lateritic soil from Ganzhou.

We previously reported that a tris-(o-phenylenediamine) iron(II) complex promotes photochemical H2 generation and C–H carboxylation of o-phenylenediamine without any additives under N2 and CO2 atmospheres, respectively, in tetrahydrofuran at room temperature. Herein, the key mechanistic process, namely, excited-state hydrogen detachment from the o-phenylendiamine moiety, is demonstrated under an N2 atmosphere.

Nanozymes have offered remarkable advantages over natural enzymes and found widespread applications including biosensors, immunoassays, nanomedicines, and environmental remediation. Oxidation of o-phenylenediamine (OPD) by nanozymes has been listed as a standard protocol for determining nanozyme activities. Given the complexity of OPD oxidation processes, however, the mechanism of nanozyme-catalyzed oxidation of OPD remains elusive. In this report, mechanistic studies of nanozyme-catalyzed oxidation of OPD are performed and a distinguishably different mechanism from that of natural enzymes is found. A combination of Fourier transform infrared spectroscopy, nuclear magnetic resonance, electrospray ionization mass spectrometry, and electron microscopic studies provides compelling evidence that polymerization of OPD occurs on the surface of several different nanozymes. The unexpected polymerization causes a dense coating layer of poly(o-phenylenediamine) (POPD) on nanozymes renders the intrinsic properties of nanozymes. Therefore, this fundamental discovery raise serious concerns using OPD-based colorimetric method for determining nanozyme activities. Without examining the surface change of nanozymes after catalytic reactions, the use of OPD-based colorimetric method for determining nanozyme activities is strongly discouraged. Furthermore, POPD is discovered as a new oxidase mimic, and this new mechanism also provides a general and robust method to coat nanomaterials with POPD polymers of enzyme-mimicking properties.

Fabricated titanate nanotubes (f-TNT) are prepared by chemical deposition method using linen fiber. The f-TNTs is fabricated by TiO2 nanoparticles, the each TiO2 nanoparticles diameter has 80-100 nm in range. The Pd0 nanoparticle was coated on the surface of the f-TNT by chemical reduction method, using NaBH4 as reducing agent. The prepared Pd/f-TNTs characterized by FT-IR, FE-SEM and HRTEM, the result shows that the f-TNT diameter is 1500 nm and Pd nanoparticles range in 20-50 nm. The Pd/f-TNT nanocomposite modified glassy carbon (GC) electrode shows quasi irreversible redox behaviours in cyclic voltammeter. Those Pd/f-TNTs modified electrode is utilized for electrochemical polymerization of o-phenylenediamine in acid medium.

The tandem synthesis of benzimidazole and other azoles can be achived by the N-formylation of ortho-substituted anilines followed by a cyclization reaction. However, CO2-based N-formylations with hydrosilane reducing agents are base catalyzed whereas the cyclization reaction is acid catalyzed. The mismatch in catalytic conditions means that only one of the steps can be catalyzed in a single pot reaction. While the N-formylation reaction is frequently the target of catalyst development, the cyclization reaction requires comparably much harsher reaction conditions. Identification of these difficulties lead us to the development of a one-pot, two-step synthesis of benzimidazole under mild reaction conditions employing acid catalysts.

We studied the exothermic laws of Fe3+/H2O2 homogeneous quasi-Fenton degradation of o-phenylenediamine in waste water, and analyzed the effects of [H2O2] and [Fe3+], initial reaction temperature, and other factors on the solution temperature elevation (Δt), temperature elevation duration (T), and chemical oxygen demand degradation rate (η) during the degradation of the target pollutant. Our study found that [H2O2] is a major factor affecting Δt, while [Fe3+] and t0 are the main factors influencing the exothermic reaction rate. For the conditions wherein [H2O2] is 0.2 mol L−1, [Fe3+] is 10 mmol L−1, pH = 7.8, initial reaction temperature is 30 °C, and reaction duration is 30 min, Δt of 200 mL of 0.04 mol L−1 o-phenylenediamine is 7.2 °C and η is 93.45%. The exothermic reaction between the free radicals (·OH and ) and o-phenylenediamine and the exothermic reaction due to auto-consumption of free radicals are the main reasons for the increased temperature of the solution.

Molecularly imprinted polymers (MIPs) mimic the binding sites of antibodies by substituting the amino acid-scaffold of proteins by synthetic polymers. In this work, the first MIP for the recognition of the diagnostically relevant enzyme butyrylcholinesterase (BuChE) is presented. The MIP was prepared using electropolymerization of the functional monomer o-phenylenediamine and was deposited as a thin film on a glassy carbon electrode by oxidative potentiodynamic polymerization. Rebinding and removal of the template were detected by cyclic voltammetry using ferricyanide as a redox marker. Furthermore, the enzymatic activity of BuChE rebound to the MIP was measured via the anodic oxidation of thiocholine, the reaction product of butyrylthiocholine. The response was linear between 50 pM and 2 nM concentrations of BuChE with a detection limit of 14.7 pM. In addition to the high sensitivity for BuChE, the sensor responded towards pseudo-irreversible inhibitors in the lower mM range., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1138

A simple and efficient method for the regioselective transmonocyanoacetylation of o-phenylenediamine derivatives was developed using 1-cyanoacetyl-3,5-dimethylpyrazole as a cyanoacetylating agent. This method provided operationally simple and efficient access to a series of N-(2-aminophenyl)-2-cyanoacetamide derivatives under mild conditions with short reaction time. Also, 2-cyanomethylbenzimidazole derivatives have been synthesized through the cyclocondensation of N-(2-aminophenyl)-2-cyanoacetamide derivatives. In all cases, high yield of products was obtained and reaction times were significantly reduced with relation to similar reactions.

The homopolymers of aniline (P(ANi)PA) and o-phenylenediamine (P(PDA)PA) along with the copolymers of PDA with aniline (ANi) (P(PDA/ANi)PA) and 3,4-ethylenedioxythiophene (P(PDA/EDOT)PA) were synthesized via a polycondensation reaction that was initiated with ammonium persulfate in the presence of pyrophosphoric acid (PA). Treating the polymers with an alkaline resulted in the generation of the corresponding neutral polymers. The content of the NH2 groups within the polymers, which contained a P(PDA) unit, was determined by analyzing the N-acetylated polymers using 1H NMR spectroscopy. Elastic gels were obtained by dipping the PA cross-linked polymers into an organic solvent. The UV–Vis spectra for P(ANi)PA and P(PDA/ANi)PA exhibited absorption peaks corresponding to the cation radical (polaron) and dication (bipolaron) bands. The electrical conductivities of P(ANi)PA and P(PDA/ANi)PA were higher than those of the corresponding neutral polymers.

This research paper deals with the synthesis and diagnose of Benzimidazole rings which were have been prepared by using two different methods in which used starting material o-phenylenediamine with different compounds. The first method is with aldehydes such as 4-Chlorobenzaldehyde, 4-N, N-Dimethylbenzaldehyde, and Formaldehyde. The second is with Carboxylic acids such as Salicylic acid, Acetic acid, and Butanoic acid. ρ-TSOH has been using as a catalyst in the synthesis methods above and used F.T.I.R and HNMR spectroscopy are used for diagnosing the prepared rings in addition to the physical properties.

Condensation of para-dibromoxylene and ortho-phenylenediamine in glass ampule at 150°С in an alkaline aqueous solution has yielded polymer with completely substituted N–H hydrogen atoms, capable of formation of polymeric cation-radicals. Complexes of this polymer and N,N,N',N'-tetrabenzyl-o-phenylenediamine with Co(II), Ni(II), Cu(II), and Ag(I) have been obtained, and their structure has been studied.

The study herein investigated the effectiveness of simultaneous use of ozone and hydrogen peroxide (O3/H2O2 process) to degrade o-phenylenediamine (o-PDA) in a simulated wastewater. A rotor–stator reactor (RSR) was employed to create a high-gravity environment in order to enhance ozone-liquid mass transfer rate and possibly improve the degradation rate of o-PDA. The degradation efficiency of o-PDA (η) as well as the overall gas-phase volumetric mass transfer coefficient (KGa) were determined under different operating conditions of H2O2 concentration, initial o-PDA concentration, temperature of reaction, initial pH and rotation speed of RSR in attempt to establish the optimal conditions. Chemical oxygen demand reduction rate (rCOD) of wastewater treated at a particular set of conditions was also analyzed. Additionally, the intermediate products of degradation were identified using a gas chromatography-mass spectrometer (GC/MS) to further evaluate the extent of o-PDA degradation as well as establish its possible degradation pathway. Results were validated by comparison with those of sole use of ozone (O3 process), and it was noted that η, KGa and rCOD achieved by O3/H2O2 process was 24.4%, 31.6% and 25.2% respectively higher than those of O3 process, indicating that H2O2 can greatly enhance ozonation of o-PDA. This work further demonstrates that an RSR can significantly intensify ozone-liquid mass transfer rate and thus provides a feasible intensification means for the ozonation of o-PDA as well as other recalcitrant organics.

A simple and efficient one-pot procedure for the synthesis of biologically interesting 3,4-dihydroquinoxalin-2-amine derivatives through a three-component condensation reaction of o-phenylenediamines, carbonyl compounds and isocyanides in ethanol at room temperature is described. In this work, unlike the other methods, aldehydes reacted as well as ketones in the presence of 10 mol% of zirconium tetrachloride as catalyst to afford good to excellent yields of products. This methodology is of great value because of its environmentally benign character, high yields, ease of handling and reliable for both aldehydes and ketones. The newly synthesized compounds were systematically characterized by IR, 1H NMR, 13C NMR and elemental analysis. A novel catalytic one-pot three-component reaction of aldehydes, o-phenylenediamine derivatives and isocyanides for synthesis of 3,4-dihydroquinoxalin-2-amine derivatives in the presence of zirconium tetrachloride .

A condensation of 2-hydroxyimino-5,5-dimethylcyclohexane-1,3-dione, ninhydrin oxime and 3-hydroxyiminopentane-2,4-dione with o-phenylenediamine in the presence of CF3COOH provided 6,6-dimethyl-6,7-dihydroquinoxalino-[2,3-a]phenazine, benzimidazo[2′,1′:1,2]isoquino[3,4-b]quinoxaline, and 2-acetyl-3-methylquinoxaline oxime, respectively. An ability to form stacking dimers was found for the second product.

A highly efficient magnetically separable nano cobalt ferrite catalyst was synthesized via the sol-gel auto combustion method, characterized by powder XRD, SEM, TEM, UV–Visible, FT-IR, magnetic study, and BET isotherm analysis. The synthesized material was found to be an efficient heterogeneous Lewis acid catalyst for the synthesis of 2-aryl benzimidazole derivatives via solvent-free mechanochemical synthesis. The notable features of this new protocol include solvent-free reaction, cost-effectiveness, good yields, and environmental friendliness to afford the products within a short reaction time along with easy recovery and reuse of the nano catalyst.

Developing ratiometric fluorescence and smartphone dual-mode bioanalysis methods is important but challenging. A ratiometric fluorescence method for determining glutathione (GSH) using carbon dots (CDs) and Ag+-triggered o-phenylenediamine (OPD) oxidation is described here. Ag+oxidizes OPD to give 2,3-diaminophenazine (oxOPD), which effectively quenches CD fluorescence at 436 nm through the inner filter effect and causes a new emission peak at 561 nm. GSH chelates with Ag+and prevents the Ag+oxidizing OPD and therefore effectively preserves CD emission at 436 nm (blue) and allows only weak oxOPD fluorescence at 561 nm (orange) to occur. The oxOPD to CD fluorescence intensity ratio decreased linearly as the GSH concentration increased in the range 0-150 nM, and the detection limit was 15 nM. The ratiometric fluorescence probe lit with an ultraviolet lamp clearly changed color from orange to blue as the GSH concentration increased. An image was acquired using a smartphone camera and converted into digital values. The blue and red channel ratio was calculated and used to quantify GSH. The method therefore allows dual-mode detection of GSH.

In this research, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been used in the condensation reaction between o-phenylenediamine and various arylaldehydes as oxidants under microwave irradiation. In this clean reaction, the benzimidazole derivatives were synthesized as benefit target products. The advantages to this procedure include high yields, easy work-up procedure, no chromatographic separation, and short reaction times. The obtained pure products were characterized by physical and spectral data such as IR, 1H NMR and 13C NMR techniques.

Conventional homogeneous and microporous heterogeneous catalysts for quinoxalines production from diamines and diketones usually suffer from difficult separation or harsh reaction conditions. Here, we demonstrate the production of various substituted quinoxalines using ZnO nanoparticle-loaded, highly ordered, mesoporous silica KIT-6 materials as solid catalysts in room temperature. The results show that the KIT-6-130-10Zn sample (aged at 130 °C and containing 10 wt% ZnO) effectively produces quinoxalines up to the maximum of 99%. We propose that the enhanced performance of the ZnO-loaded KIT-6 materials resulted from the homogeneous distribution of ZnO nanoparticles, along with the KIT-6's high specific surface area and large pore sizes.

Two bis-benzimidazolium salts 1,4-bis[n′-(N-benzyl-benzimidazolium-N′-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate (L1H2·(PF6)2 and L3H2·(PF6)2) and two bis-imidazolium salts 1,4-bis[n′-(N-benzyl-imidazolium-N′-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate (L2H2·(PF6)2 and L4H2·(PF6)2) (n = 2 or 3), as well as their four macrometallocycle binuclear N-heterocyclic carbene silver(I) complexes [(L1Ag)2](PF6)2 (1), [(L2Ag)2](PF6)2 (2), [(L3Ag)2](PF6)2 (3) and [(L4Ag)2](PF6)2 (4) were prepared and characterized. In complexes 1–4, each macrometallocycle (30-membered macrometallocycle for 1 and 2, 34-membered macrometallocycle for 3 and 4) was formed by two biscarbene ligands (L1–L4 for 1–4) and two silver(I) ions. In the crystal packings of 1–4, 2D supramolecular layers are formed via intermolecular weak interactions including hydrogen bonds and π–π interactions. Additionally, the selective recognition of o-phenylenediamine (OPD) using 4 as a host compound was investigated using fluorescence and UV/vis titrations. The results indicate that 4 can distinguish effectively o-phenylenediamine from other aromatic amines.

The synthesis of 2-substituted benzimidazoles from the reaction of o-phenylenediamine and an imino ester hydrochloride with ultrasound irradiation is reported. The procedure has an eco-friendly and simple workup with good yield in a short time.

Considering the biological properties of the compounds containing quinoxaline and indandione skeleton, a new thiolate salt was synthesized via the reaction between ninhydrin and phenacyl thiocyanate in the presence of triethylamine and in continuous, from the reaction of this thiolate with methyl iodide and o-phenylenediamine in absolute ethanol, quinoxaline containing indandione substituent was obtained.

Polymer supported sulphanilic acid was synthesized and used as green, reusable and heterogeneous catalyst and duly characterized using chemical methods like determination of free hydroxyl content, epoxy equivalent weight and free sulphonic acid content as well as infrared spectroscopy and thermogravimetric analysis. The prepared catalyst was applied for one-pot synthesis of 2-substituted benzimidazoles from o-phenylenediamine and various aromatic aldehydes in absolute ethanol under thermal condition. Catalyst was separated from the product by simple filtration and could be reused for at least five times with almost retention in its efficiency. Due to three dimensional network structures, it shows high thermal stability and can be reused without any further purification.

Zirconocene dichloride (Cp2ZrCl2) in the presence of ethanol is found to be a highly efficient catalyst for the one-pot synthesis of structurally diverse 2-substituted benzimidazole derivatives by reaction of o-phenylenediamine and aromatic aldehydes at ambient temperature.

An efficient p-toluenesulfonic acid catalyzed synthesis of 11H-benzo[a]benzo[6,7]chromeno[2,3-c]phenazine-11,16(17H)-dione derivatives has been described by one-pot, four-component condensation of 2-hydroxynaphthalene-1,4-dione, o-phenylenediamine, aromatic aldehydes using polyethylene glycol as solvent. This domino protocol produces biologically considerable heterocycles with the formation of C–C, C=C, C–N, C=N, C–O bonds in a single operation and this efficient green process provides significant advantages such as: operational simplicity, easy work-up procedure, high yields, avoidance of hazardous or toxic catalysts and organic solvents, and is devoid of inessential derivatization and generation of hazardous substances.

Strongly yellow fluorescent carbon dots (CDs) have been directly synthesized from o-phenylenediamine (o-PD) through a facile microwave-assisted method. The as-prepared o-CDs exhibit excitation-dependent photoluminescent behavior and excellent water-solubility due to some amino or hydroxy functional groups on the surface. An emission peak appears at 573 nm when the o-CDs solution is excited at 400 nm, and the quantum yield (QY) is 38.5%. Owing to their low toxicity and water solubility the as-prepared o-CDs can be directly used for cell imaging. More importantly, the as-prepared o-CDs solution also shows sensitivity for H2O2. The limits of detection (LOD) for Fe3+ and H2O2 are 16.1 nM and 28.1 nM, respectively, which is much lower than what's reported in previous studies. The fluorescence intensity also shows a dependence on pH and the strongest fluorescence intensity appears at pH 9. In addition, we also find that the fluorescent properties of CDs prepared from m-phenylenediamine (m-PDs) and p-phenylenediamine (p-PDs) are quite different from those of o-CDs.

In this paper, we demonstrated a fluorescent o-phenylenediamine–m-phenylenediamine copolymer sensing system, which was synthesized by a facile and one-step hydrothermal method. The copolymer was first used as fluorescent probe for the detection of Chromium(VI) ion (Cr 6+ ) and showed high selectivity and sensitivity. The detection limit was 1×10 −11 M. It showed excellent linear relationships in wide range of 7×10 −11 –6×10 −10 M. Moreover, the addition of ethylenediaminetetraacetate (EDTA) to the detection system could successfully combine with Cr 6+ to form metal chelates, making the fluorescence recovery of o-phenylenediamine–m-phenylenediamine copolymer. What is important, the prepared process had no addition of initiating agent.

A novel method was developed for synthesizing a series of new three dentate Schiff base ligands starting from hydroxynaphthalidene pyrimidinyl amines with o-phenylenediamines or o-aminophenol or 2-amino-3-hydroxy-pyri-dine in the presence of formic acid catalyst under solvent-free conditions. In these reactions [1+1] condensation product as half-unit ligand was obtained. Moreover, the reaction of hydroxynaphthalidene pyrimidinyl amines with 3,4-diamino-pyridine and 1,8-naphthalenediamine lead to the formation of C2-naphthylated imidazopyridine and dihydropyrimidine, respectively. The attractive features of this protocol are: use of inexpensive catalyst, operationally simple, short reaction times, easy handling, and good yields.

In this study, an effective and novel method was developed to improve the thermal conductivity of epoxy composites by functionalization of graphene. The functionalization of graphene was carried out with a simple refluxing method using a double N-precursor with O-phenylenediamine (OPD), in which the graphene was first treated with acid (2 : 6 molar H2SO4 : HNO3) to form oxygen containing groups on the graphene surface (O-graphene). Amidation and nucleophilic addition reactions through amine groups in OPD contributed significantly to the doping of nitrogen into the graphene layers. The OPD functionalized graphene (OPD-f-graphene) was highly effective and compatible with an epoxy matrix, resulting in homogenous dispersion of a filler in the matrix. The in-plane and through-plane thermal conductivity of the functionalized graphene filled epoxy composite (fG–epoxy) was significantly increased ∼13 fold and ∼4.8 fold, respectively, in comparison to the neat epoxy composite (G–epoxy) with the addition of 6 wt% of the filler. This improvement in thermal conductivity was attributed to better dispersion of the filler into fG–epoxy which generated phonon conduction pathways.

The reaction of o-phenylenediamine with 2-alkoxypropenals at room temperature affords 2-(1-alkoxyvinyl)benzimidazoles (53–68%), while 2-hydroxy-3-arylpropenals give 2-(arylmethyl) quinoxalines (85–86%).

Heating an equimolar mixture of opianic acid and o-phenylenediamine in MeOH or EtOH produced 2-(2-carboxy-3,4-dimethoxyphenyl)benzimidazole, which was readily dehydrated in refluxing acetic or propionic anhydride to 11H-1,2-dimethoxyisoindolo[2,3-a]benzimidazol-11-one. Analogous reactions were carried out with 4,5-dichloro-o-phenylenediamine.

A base-catalyzed conversion of aldehydes to benzimidazoles has been achieved. The compounds have been characterized by IR, NMR, micoranalysis, and GC-MS. The reaction for the formation of benzimidazoles has been monitored with 1 H NMR and IR. The crystal structures of two derivatives, 2-(2-chlorophenyl)-1 H -benzimidazole and 2-(1 H -benzimidazol-2-yl)-4-nitrophenol, are presented. A study of the DPPH scavenging activity of these compounds showed that 2-(1 H -benzimidazol-2-yl)phenol ( 2 ), 2- p -tolyl-1 H -benzimidazole ( 3 ) and 2-(4-methoxyphenyl)-1 H -benzimidazole ( 7 ) gave IC 50 values 1974, 773 and 800 µM. KEY WORDS : Benzimidazole, o -Phenylenediamine, Aldehydes, Base catalysis, DPPH scavenging activity Bull. Chem. Soc. Ethiop. 2018 , 32(2), 271-284. DOI: https://dx.doi.org/10.4314/bcse.v32i2.8

A method is presented for surface encapsulation of nano-Fe3O4 by o-phenylenediamine via cross-linking using formaldehyde and glutaraldhyde for the formation of two newly designed magnetic nano-sorbents. These have been characterized by FT-IR, TGA, and SEM and maintained the magnetic and thermal stability characters. The metal capacity values of Pb(II) and Cd(II) have been optimized in presence of different physico-chemical parameters and confirmed the superior selectivity for Pb(II). Maximum capacity values of Pb(II) (7000-10000 ± 250-675 µmol g−1) and Cd(II) (1500-2250 ± 30-75 µmol g−1) at optimum conditions and excellent extraction values (94.10-100.0 ± 1.2-3.5%) from industrial wastewater have been identified.

In this research, ZnS nanoparticles were prepared and applied as heterogeneous reusable catalyst for synthesis of 1,5-benzodiazepines under grinding conditions at 70 °C. The multi-component reactions of aldehydes, dimedone and o-phenylenediamine were carried out under grinding conditions to obtain some 3,3-dimethyl-2,3,4,5,10,11-hexahydro-11-[aryl]-1H-dibenzo[b,e][1,4] diazepine-1-one derivatives. The present approach provides several advantages, including high yields, short reaction times, little catalyst loading and purification of compounds by crystallization method. The catalyst was characterized by using FT-IR, XRD, PL, EDX, SEM and TEM techniques.

A one-pot, two-step procedure has been used to synthesize functionalized benzo[a]pyrano[2,3-c]phenazine derivatives from a four-component condensation reaction of 2-hydroxynaphthalene-1,4-dione, o-phenylenediamine, aldehydes, and malononitrile in the presence of 1,3,7-trimethylpurine-2,6-dione (caffeine) as an expedient and reusable solid base catalyst. This new procedure has the following advantages: operational simplicity, short reaction times, environmentally friendly, easy work-up, and all the products were obtained in excellent yields.