[Show abstract][Hide abstract] ABSTRACT: A stable and efficient phosphorus-free, low Pd-loading heterogeneous nanocatalyst comprising palladium and a multi-walled carbon nanotube was prepared and characterized by various techniques such as SEM, TEM, AFM, FT-IR, and Raman spectrometry, [Formula: see text] adsorption isotherm and thermogravimetric analysis. This catalyst was used for the deprotection of phenol ethers. The catalyst selectivity for deprotection of between propargyl, allyl, and benzyl, as a protecting group, was studied. Also, the presence of different functional groups was studied to establish the scope and limitations of this method. The catalytic activity of recycled catalyst was evaluated. The results indicated that the catalyst is heterogeneous, stable, and very active under the established conditions, and it could be reused up to five times without any significant leaching. In addition, according to ICP analysis, low leaves of leaching of palladium from the catalyst was observed, which indicates that anthraquinone has an excellent ability to coordinate with palladium.
[Show abstract][Hide abstract] ABSTRACT: A highly active, air-stable, and versatile procedure for Buchwald-Hartwig and Sharpless-Meldal C-N bond formation is reported. Under nearly solvent-free conditions using copper(II) acetate and 2-phenyl-2-(4-phenyl-1H-1,2,3-triazol-1-yl)ethanol, a variety of N-heterocycles and various cyclic and noncyclic secondary amines were arylated to form N-aryl compounds in moderate to excellent yields. This methodology also provides rapid access to diverse 1,4-disubstituted 1,2,3-triazoles in good to excellent yields. All reactions are performed in short times under air.
[Show abstract][Hide abstract] ABSTRACT: High yielding preparation of structurally different anthraquinone lariat ethers from the reaction of a novel anthraquinone aza crown ether 3 with a variety of substituted phenols and paraformaldehyde in the presence of zinc oxide nanoparticles at 100°C in a solvent-free condition has been described. The procedure of these reactions is very simple, the yields are generally high to excellent, and the method is applicable to large scale operation without any problem. Furthermore, the zinc oxide nanoparticles could be recovered and recycled up to five times by simple filtration of the reaction mixture.
Journal of Heterocyclic Chemistry 02/2015; DOI:10.1002/jhet.1811 · 0.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mo(IV) salen complex (2.5 mol%) was found to be a highly efficient catalyst for the one-pot synthesis of 2,4,5-triarylimidazoles via a three-component reaction using benzil or benzoin, aryl aldehydes, and ammonium acetate as a nitrogen source under mild conditions. In order to recover and the reuse of the catalyst, a new Mo(IV) salen–silica nanoparticle as heterogeneous catalyst was prepared by simple and successful immobilization of the catalyst onto silica (3-aminopropyl functionalized silica gel). This procedure can be applied to large-scale conditions with high efficiency. Experimental evidence showed that the catalyst is stable and can be easily recovered and reused for at least five times without significant loss of activity. The nanocatalyst was characterized using FT-IR spectroscopy, scanning electron microscopy, atomic force microscopy, powder X-ray diffraction , transmission electron microscopy, thermogravimetric instrument for analysis of nitrogen adsorption, and inductively coupled plasma spectrometer.
[Show abstract][Hide abstract] ABSTRACT: An efficient synthesis of 2H-indazole derivatives based on the one-pot three-component reaction of 2-chloro- and 2-bromobenzaldehydes, primary amines and sodium azide is described. The reaction is catalyzed by copper(I) oxide nanoparticles (Cu2O-NP) under ligand-free conditions in polyethylene glycol (PEG 300) as a green solvent.
[Show abstract][Hide abstract] ABSTRACT: The bactericidal efficiency of various positively and negatively charged silver nanoparticles has been extensively evaluated in literature, but there is no report on efficacy of neutrally charged silver nanoparticles. The goal of this study is to evaluate the role of electrical charge at the surface of silver nanoparticles on antibacterial activity against a panel of microorganisms. Three different silver nanoparticles were synthesized by different methods, providing three different electrical surface charges (positive, neutral, and negative). The antibacterial activity of these nanoparticles was tested against gram-positive (i.e., Staphylococcus aureus, Streptococcus mutans, and Streptococcus pyogenes) and gram-negative (i.e., Escherichia coli and Proteus vulgaris) bacteria. Well diffusion and micro-dilution tests were used to evaluate the bactericidal activity of the nanoparticles. According to the obtained results, the positively-charged silver nanoparticles showed the highest bactericidal activity against all microorganisms tested. The negatively charged silver nanoparticles had the least and the neutral nanoparticles had intermediate antibacterial activity. The most resistant bacteria were Proteus vulgaris. We found that the surface charge of the silver nanoparticles was a significant factor affecting bactericidal activity on these surfaces. Although the positively charged nanoparticles showed the highest level of effectiveness against the organisms tested, the neutrally charged particles were also potent against most bacterial species.
Journal of Nanomaterials 09/2014; 2015(2015):8. DOI:10.1155/2015/720654 · 1.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Copper(I) oxide nanoparticles (CONPs) catalyze multicomponent coupling/cycloisomerization reactions between various 2-hydroxybenzaldehydes, secondary amines, and nonactivated alkynes to give 2,3-disubstituted 1-benzofurans. All reactions are carried out under solvent-and ligand-free conditions at 100 degrees C in air. The combination of copper-catalyzed C-H activation and an O-annulation process is essential for this transformation. This methodology provides rapid access to substituted 1-benzofurans in good to excellent yields with high atom economy and high catalytic efficiency. This procedure eliminates the need for propargylamine derivatives, uncyclized intermediates that make purification difficult. The CONPs and tetrabutylammonium bromide were reused successfully for up to five times.
[Show abstract][Hide abstract] ABSTRACT: AimTo synthesize and characterize silver nanoparticles (Ag NPs) with different surface charges in order to evaluate their cytotoxicity and antibacterial activity in the absence and presence of dentine compared with NaOCl and CHXMethodologyAg NPs with positive, negative and neutral surface charges were synthesized and characterized. The first phase of the experiment determined the minimum inhibitory concentrations (MICs) of NPs against planktonic E. faecalis and compared them with that of NaOCl and CHX. The second phase tested the elimination of E. faecalis at different contact times (5, 20 and 60 min and 4 and 24 h) and the role of dentine in their inactivation was assessed. In the third phase, the most effective Ag NP solution was selected for cytocompatibility assessment. An MTT-based cytotoxicity assay was used to evaluate the cytotoxicity of the selected NP solution in different concentrations on L929 fibroblasts compared to that of 2.5% NaOCl and 0.2% CHX. Student's t test and repeated measures MANOVA approach were used for statistical analyses.ResultsThe characterization revealed synthesis of colloidal NPs in the size ranges of 5–10 nm in diameter. The results indicated that Ag NP with a positive surface charge had the smallest MIC against planktonic E. faecalis and it was active in very lower concentrations compared to NaOCl, CHX and the other tested AgNPs. Positive-charged Ag NPs at 5.7×10−10 mol/L completely prevented growth of E. faecalis after 5 min of contact time, a finding comparable to 0.025% NaOCl. Dentine powder had variable inhibitory effects on all tested materials after 1 h incubation period but after 24 h, NaOCl and the positive-charged Ag NPs were not inhibited by dentine at any concentration used. CHX was the most and the positively charged Ag NP solution was the least toxic solutions to L929 fibroblasts (P < 0.001).Conclusions
Ag NP surface charge was important in bactericidal efficacy against E. faecalis. The positively charged imidazolium-based ionic-liquid protected Ag NPs showed promising antibacterial results against E. faecalis and exhibited a high level of cytocompatibility to L929 cells.This article is protected by copyright. All rights reserved.
International Endodontic Journal 09/2014; 48(8). DOI:10.1111/iej.12377 · 2.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, the combination of 7,8-dihydroxy-4-methyl coumarin (DHMC) as a novel bidentate O,O-chelating agent and copper(II) acetate monohydrate (2:1 molar ratio) has been found to form an efficient catalytic system. This catalyst provided good to excellent yields in the multi-component click synthesis of 1,4-disubstituted-1,2,3-triazoles by using various structurally diverse organic halides, different non-activated terminal alkynes, and sodium azide. This catalytic system eliminates the need for the isolation of the hazardous azide intermediates which are generated in situ. The reaction is carried out in aqueous phase at room temperature and it can be accelerated by sonication or by increasing the reaction temperature. Moreover, the reaction can be performed in large scale. It is noteworthy that DHMC is commercially available and that it can be easily synthesized with low cost materials.
[Show abstract][Hide abstract] ABSTRACT: A coated wire Fe2+ ion selective electrode based on laboratory-synthesized crown ether, as a neutral carrier, was constructed. The effects of different experimental parameters such as the amount of plasticizer, the amount of ionophore, pH of the sample solution, and coexisting ions on the potentiometric responses of the electrode were investigated. The electrode exhibited a Nernstian slope of 29.20 +/- 0.87 mV/decade over a wide concentration range of 7.2 x 10(-7) - 6.9 x 10(-3) M Fe2+. The potentiometric responses were independent of the pH of the test solution in the pH range of 4.6-9.6. The response time and detection limit were found to be 3.0 min and 6.7 x 10(-7) M, respectively. The electrode revealed good selectivity for Fe2+ in the presence of different coexisting cations and anions. It was certified as an indicator electrode by performing a potentiometric titration for a standard sample of Fe2+ ion.
[Show abstract][Hide abstract] ABSTRACT: In this paper, a novel heterogeneous complex of zinc with N,N-bis(2-hydroxyphenyl)pyridine-2,6-dicarboxamide(BHPPDAH) was synthesized. The catalyst was found to be a highly effective catalyst for the three-component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) via C-H activation. The reactions could be applied to both aromatic and aliphatic aldehydes and alkynes. Nearly quantitative yields of the desired products were obtained in most cases. The reaction proceeds without any cocatalyst or activator, and water is the only byproduct. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for five cycles with almost consistent activity.
[Show abstract][Hide abstract] ABSTRACT: A poly (vinyl chloride) (PVC) matrix membrane ion-selective electrode for silver (I) ion is fabricated based on modified polypyrrole - multiwalled carbon nanotubes composite with new lariat ether. This sensor has a Nernstian slope of 59.4±0.5mV/decade over a wide linear concentration range of 1.0×10(-7) to 1.0×10(-1)molL(-1) for silver (I) ion. It has a short response time of about 8.0s and can be used for at least 50days. The detection limit is 9.3×10(-8)molL(-1) for silver (I) ion, and the electrode was applicable in the wide pH range of 1.6 -7.7. The electrode shows good selectivity for silver ion against many cations such as Hg (II), which usually imposes serious interference in the determination of silver ion concentration. The use of multiwalled carbon nanotubes (MWCNTs) in a polymer matrix improves the linear range and sensitivity of the electrode. In addition by coating the solid contact with a layer of the polypyrrole (Ppy) before coating the membrane on it, not only did it reduce the drift in potential, but a shorter response time was also resulted. The proposed electrode was used as an indicator electrode for potentiometric titration of silver ions with chloride anions and in the titration of mixed halides. This electrode was successfully applied for the determination of silver ions in silver sulphadiazine as a burning cream.
[Show abstract][Hide abstract] ABSTRACT: A novel optode for determination of Hg(II) ions is developed based on immobilization of a recently synthesized ionophore, 7-(1H-imidazol-1-ylmethyl)-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10 benzodioxatriaza cyclopentadecine-3,11(4H,12H)-dione, in a PVC membrane. Dioctyl sebacate was used as a plasticizer, sodium tetraphenylborate as an anionic additive and ETH5294 as a chromoionophore. The response of the optode was based on the complexation of Hg(II) with the ionophore in the membrane phase, resulting an ion exchange process between Hg(II) in the sample solution and H(+) in the membrane. The effects of pH and amounts of the ionophore, chromoionophore, ionic additive and type of plasticizer on the optode response were investigated. The selectivity of the optode was studied in the present of several cations. The optode has a linear response to Hg(II) in the range of 7.2×10(-13)-4.7×10(-4)molL(-1) with detection limit of 0.18pmolL(-1). The optode was successfully applied to the determination of Hg(II) in real samples.
[Show abstract][Hide abstract] ABSTRACT: The efficient synthesis of chromeno[3,4-[Formula: see text]]quinoline derivatives by condensation of O-propargylated salicylaldehyde, or corresponding compounds and primary aromatic amine derivatives using a catalytic amount of heterogeneous Cu(II)BHPPDAH complex without being immobilized on any supports (5.0 mol%) in PEG 300 as a "green" solvent is described. The remarkable features of this protocol are good to high yields in all cases, short reaction times, a cleaner reaction profile in an environmentally benign solvent (PEG 300), and the method is applicable to large-scale operation without any problem. Furthermore, the catalyst was quantitatively recovered from the reaction mixture by simple filtration and reused at least seven times with almost consistent activity.
[Show abstract][Hide abstract] ABSTRACT: 5-Substituted-1H-tetrazoles can conveniently be synthesized from the corresponding nitriles by reaction with NaN3 using the efficient and recyclable heterogeneous catalyst prepared by immobilization of copper(II) complex of 4′-phenyl-2,2′:6′,2″-terpyridine on activated multi-walled carbon nanotubes [AMWCNTs-O–Cu(II)–PhTPY]. Excellent results were obtained in each case affording the corresponding tetrazole adducts in good to excellent yields. In general, aromatic nitriles with electron-donating group could be accomplished as well as that with electron-withdrawing groups. By leaving out nitrile from the reaction and adding CH(OEt)3 and amines bearing various substituents, 1-substituted-1H-tetrazoles formed in water in high yields. The reported protocols have the advantages of rapid assembly of a host of heterocyclic systems in high yields with the added advantage of recycling and reuse of the catalyst.
[Show abstract][Hide abstract] ABSTRACT: We report on the synthesis of polymeric nanoparticles (PNPs) containing a tetrakis(3-hydroxyphenyl)porphyrin, and their use for the separation of mercury(II) ion. The PNPs were prepared by bulk polymerization from methacrylic acid (the monomer), ethyleneglycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the radical initiator) and the mercury(II) complex of 5,10,15,20-tetrakis(3-hydroxyphenyl)-porphyrin. The Hg(II) ion was then removed by treatment with dilute hydrochloric acid. The PNPs were characterized by colorimetry, FT-IR spectroscopy, and scanning electron microscopy. The material is capable of binding Hg(II) from analyte samples. Bound Hg(II) ions can be eluted with dilute nitric acid and then quantified by cold vapor AAS. The extraction efficiency, the effects of pH, preconcentration and leaching times, sample volume, and of the nature, concentration and volume of eluent were investigated. The maximum adsorption capacity of the PNPs is 249 mg g−1, the relative standard deviation of the AAS assay is 2.2 %, and the limit of detection (3σ) is 8 ng.L−1. The nanoparticles exhibit excellent selectivity for Hg(II) ion over other metal ions and were successfully applied to the selective extraction and determination of Hg(II) ion in spiked water samples.
Schematic presentation of leaching process of mercury(II) ion from the prepared IIP