Tài liệu miễn phí Hoá học
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One-pot multicomponent synthesis of piperidinium 3,3’-(arylmethylene) bis (2-hydroxynaphthalene-1,4-diones): NMR spectroscopic and X-ray structure characterization
A facile synthesis of piperidinium 3,3’-(arylmethylene) bis (2-hydroxynaphthalene-1,4-dione) analogs as organic salts is described by the one-pot pseudo-four-component reaction between 2-hydroxy-1,4-naphthoquinone, aromatic aldehydes, and piperidine. The single-crystal X-ray diffraction analysis of these systems confirms that the stabilized predominant interactions are N-H...O and O-H...O hydrogen bonds. Mild and clean reaction conditions, high atom economy, and operational simplicity of this one-pot multicomponent reaction coupled with excellent yields and no need for column chromatography have transformed this procedure to be a superior synthetic route for the efficient formation of families of naphthoquinone-derived compounds.
4/3/2023 10:17:07 PM +00:00
Synthesis, solvatochromism, and biological activity of novel azo dyes bearing 2-pyridone and benzimidazole moieties
New azo dyes bearing 2-pyridone and benzimidazole moieties were prepared using diazotization of 4-(1Hbenzo[d]imidazol-2-yl)aniline and coupling of the obtained diazonium salt with substituted 3-cyano-2-pyridones. Obtained compounds were characterized via UV-Vis, FT-IR, and 1H and 13C NMR spectroscopy as well as by elemental analysis data. The UV-Vis spectra of the synthesized dyes were measured in thirteen solvents of different properties at room temperature. Solvatochromism and tautomerism of novel azo dyes were discussed.
4/3/2023 10:17:01 PM +00:00
Efficient reductive Claisen rearrangement of prop-2’-enyloxyanthraquinones and 2’-chloroprop-2’-enyloxyanthraquinones with iron powder in ionic liquids
A rapid and selective iron-mediated reductive Claisen rearrangement of various prop-2’-enyloxyanthraquinones and 2’-chloroprop-2’-enyloxyanthraquinones to 1-hydroxy-2-(prop-2’-enyl)anthraquinones and anthrafurandiones is presented. All reactions are carried out in a mixture of ionic liquids, [Bzmim]Cl (1-benzyl-3-methylimidazolium chloride) and [Hmim]BF4 (1-methylimidazolium tetrafluoroborate), in short reaction times (5–35 min). Our study showed that 1-(prop-2’-enyloxy)anthraquinone is more active than 1-(2’-chloroprop-2’-enyloxy)anthraquinone to perform this rearrangement.
4/3/2023 10:16:51 PM +00:00
Computational investigation of intramolecular reorganization energy in diketopyrrolopyrrole (DPP) derivatives
Intramolecular reorganization energy (RE) of molecules derived from the diketopyrrolopyrrole (DPP) unit has been studied using B3LYP/6-31G(d,p) theory. It was found that the replacement of the oxygen atoms with sulfur in the DPP unit led to a smaller RE for both the hole and electron transfer processes. One disadvantage of the sulfur replacement is the twist of the conjugated backbone, which might impair the π − π interactions in the solid state. The RE calculated from the adiabatic potential energy surfaces and that derived from the normal mode analysis agreed well for both systems.
4/3/2023 10:16:40 PM +00:00
Analysis of electrochemical noise in NiCd batteries throughout their lifetime
Electrochemical noise measurements have been applied to electrochemical systems that show stochastic behavior. The standard area of study that benefits from this stochastic analysis is localized corrosion modes like pitting and crevice corrosion. Application of electrochemical noise measurements to battery systems, though rare, is recently becoming more popular. The present contribution first establishes a method of analyzing electrochemical voltage noise data for NiCd batteries, then follows four samples of batteries in terms of voltage noise throughout their lifetimes. The noises exhibited by battery systems are small, but finite. This noise is expected to be due to variations in the electrochemistry on the electrode surfaces of the battery.
4/3/2023 10:16:08 PM +00:00
Synthesis and evaluation of novel 1,3,4-thiadiazole–fluoroquinolone hybrids as antibacterial, antituberculosis, and anticancer agents
A series of 5-substituted-1,3,4-thiadiazole-based fluoroquinolone derivatives were designed as potential antibacterial and anticancer agents using a molecular hybridization approach. The target compounds 16–25 were synthesized by reacting the corresponding N-(5-substituted-1,3,4-thiadiazol-2-yl)-2-chloroacetamides with ciprofloxacin or norfloxacin. The purity and identity of the synthesized compounds were determined by the use of chromatographic and spectral techniques (NMR, IR, MS, etc.) besides elemental analysis. Antibacterial, antituberculosis, and anticancer activity of the target compounds were evaluated against selected strains and cancer cell lines.
4/3/2023 10:15:53 PM +00:00
An ionic liquid/bismuth film-modified sensor for the electrochemical detection of cefixime
A highly sensitive and simple method based on an ionic liquid/ex situ bismuth film-modified single-use pencil graphite electrode (IL/Bi/PGE) was offered for the electrochemical detection of cefixime (CEF) for the first time. The synergistic effects of the ionic liquid and bismuth film combination as the surface modifier remarkably improved the electrochemical response of the modified sensor. Anodic oxidation of CEF was observed at 0.9 V vs. Ag/AgCl/3 M KCl as one well-defined irreversible oxidation peak.
4/3/2023 10:15:39 PM +00:00
The first synthesis and antioxidant and anticholinergic activities of 1-(4,5-dihydroxybenzyl)pyrrolidin-2-one derivative bromophenols including natural products
We report herein the first synthesis of biologically active natural bromophenols, namely 1-(2,3,6-tribromo4,5-dihydroxybenzyl)pyrrolidin-2-one (2), 2RS-1-(2,3-dibromo-4,5-dihydroxybenzyl)-5-oxopyrrolidine-2-carboxylic acid (3), and 2RS-methyl 1-(2,3-dibromo-4,5-dihydroxybenzyl)-5-oxopyrrolidine-2-carboxylate (4), along with their different derivatives (6 and 8–18). Among the synthesized compounds, 3, 4, and their derivatives (8 and 9) are yielded in racemic form. Radical scavenging assays of the synthesized molecules were investigated using various bioanalytical antioxidant methods including 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) and 2,2-diphenyl-1- picrylhydrazyl (DPPH•).
4/3/2023 10:15:17 PM +00:00
A simple automated microplate method for determining reducing sugars in food extracts and synthetic serum using cupric-neocuproine as reductant
In the present work, a simple automated microplate method based on cupric ion reduction is described for determining total reducing sugars in food extracts and synthetic serum. The reaction of Cu(II)-Nc (cupric-neocuproine) with reducing sugars was performed in alkaline medium in microplates, and the absorbance of the formed highly colored Cu(I)-Nc chelate in a plate reader at 450 nm was recorded. The proposed method was applied to reducing sugars (glucose, fructose, galactose, maltose, and lactose) and their linear calibration curves were constructed. The detection and quantification limits (LOD and LOQ) for glucose were 0.14 and 0.46 µM, respectively.In the present work, a simple automated microplate method based on cupric ion reduction is described for determining total reducing sugars in food extracts and synthetic serum. The reaction of Cu(II)-Nc (cupric-neocuproine) with reducing sugars was performed in alkaline medium in microplates, and the absorbance of the formed highly colored Cu(I)-Nc chelate in a plate reader at 450 nm was recorded. The proposed method was applied to reducing sugars (glucose, fructose, galactose, maltose, and lactose) and their linear calibration curves were constructed. The detection and quantification limits (LOD and LOQ) for glucose were 0.14 and 0.46 µM, respectively.
4/3/2023 10:15:08 PM +00:00
Electrochemical behavior and voltammetric determination of some nitro-substituted benzamide compounds
Voltammetric behaviors of six nitro-substituted benzamides, which are potential prodrug candidates for nitroreductase-based cancer therapy, were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrochemical behavior of aromatic nitro (ArNO2) compounds by CV indicates that compounds involve various reduction/oxidation steps including the formation of aromatic nitro radical, nitroso, hydroxylamine, and amine groups. Applicability of the voltammetric determination of these prodrug candidates was studied by recording their DPVs, carried out in mixed media (Britton Robinson buffer solution + DMF) at various pH values on a pencil graphite electrode (PGE).
4/3/2023 10:14:58 PM +00:00
Synthesis and characterizations of novel thiazolyl-thiadiazole derivatives as telomerase activators
Pyridine-3/4-thiocarboxamide derivatives were used as starting materials for the synthesis of the target compounds. The pyridine-3/4-thiocarboxamide derivatives were reacted with ethyl 2-chloroacetoacetate in ethanol to give the thiazole derivatives (1, 2). The two ethyl thiazole-carboxylate derivatives (1, 2) thus obtained were treated with sodium hydroxide solution and ethanol and converted to carboxylic acids (3, 4). The carboxylic acid derivatives (3, 4) were reacted with thiosemicarbazide in phosphoroxy trichloride and aminothiadiazole rings (5, 6) were formed. Thus, two thiazolyl-thiadiazole amine derivatives (5, 6) were obtained.
4/3/2023 10:14:49 PM +00:00
Synthesis of some ketones via nano-nickel oxide catalyzed acylation of arylzinc reagents; strategy involving the use of mixed (methyl)(aryl)zincs
Nano-NiO catalyzed acylation of mixed (methyl)(aryl)zincs with aromatic acyl halides in THF at room temperature provides a new facile route for aryl–aroyl coupling. Among NiCl2.L2 and NiCl2.L (L = monodentate and bidentate phosphine ligand) catalysts, the lower catalyst loading of NiCl2 (dppf) may seem attractive; however, nano-NiO, being the lowest cost catalyst, is more favorable for aroylation of (methyl)(aryl)zincs. This procedure also provides a supplement to Cu and Pd catalyzed acylation of diorganozincs.
4/3/2023 10:14:42 PM +00:00
Optimizing the coagulation/flocculation process for bentonite suspension with poly(acrylamide-co-(N-methyl-4-vinylpyridinium tosylate)) [AM7/VP10/0.1%/CTs]
In this work, we are interested in the quaternization of poly(acrylamide-co-4-vinylpyridine) [AM7/VP10/0.1%/] by the methyl-tosylate CH3 TS. The obtained copolymer poly(acrylamide-co-(N-methyl-4-vinylpyridinium tosylate)) [AM7/VP10/0.1%/CTs] has been characterized by 1 H NMR and UV-Vis spectroscopy. The macromolecular weight was determined by size exclusion chromatography as well as by viscosity. With the aim of removing turbidity by coagulationflocculation from bentonite suspensions, the prepared copolymer was used as a flocculant. Several important parameters in the flocculation process, such as pH of water, initial turbidity, and flocculant concentration, were utilized for the optimization of wastewater treatment.
4/3/2023 10:14:30 PM +00:00
Environmental impact assessment of natural radioactivity and heavy metals in drinking water around Akkuyu Nuclear Power Plant in Mersin Province
The aim of this study was to determine natural radioactive and heavy element concentrations in Mersin drinking water samples before the commissioning of the Akkuyu nuclear power plant and to collect data for possible environmental contaminations in the future. Drinking water samples were taken from the provincial center, districts, and populated villages. The annual effective dose of natural radionuclides and cancer risks were calculated for each person living in the city. Hazard index and cancer risk were calculated, which were caused by heavy elements.
4/3/2023 10:14:20 PM +00:00
One-pot synthesis of substituted 4H -chromenes by nickel ferrite nanoparticles as an efficient and magnetically reusable catalyst
Nickel ferrite magnetic nanoparticles (NiFe2O4MNPs) were prepared via the autocombustion assisted solgel method. The efficient catalyst was investigated by FT-IR, XRD, ICP, SEM, and TEM techniques. A one-pot, three-component reaction is reported for the synthesis of substituted 4H -chromenes in the presence of NiFe2O4 MNPs as a reusable catalyst in a green solvent at 40◦C under clean, efficient, and mild conditions. Furthermore, selected products were characterized by FT-IR, 1H NMR, and 13C NMR. The single-crystal X-ray analysis of product 4u was also conclusively confirmed. Easy workup procedure, high purity of products via simple recrystallization, and environmentally benign conditions are the outstanding benefits of this method.
4/3/2023 10:14:08 PM +00:00
Synthesis and characterization of novel unsymmetrical phthalocyanine/TiO2 composites and their evaluation as photocatalysts for degradation of 4-chlorophenol under visible light
We prepared novel unsymmetrical A3B-type zinc and cobalt phthalocyanines bearing monocarboxylic acid groups on peripheral positions using statistical condensation method, especially designed to anchor on the TiO2 semiconductor surface. The novel complexes were anchored on TiO2 semiconductor to prepare effective dye sensitized photoactive composites as heterogeneous catalysts. The results indicated that modified TiO2 nanocrystals possessed only the anatase phase and MPc-TiO2 photocatalysts with loading amount of dye ca. 8.27 µmol/g TiO2 exhibit strong visible light absorption.
4/3/2023 10:13:56 PM +00:00
Photocatalytic degradation of the herbicide quinclorac in water using Mn (III) salen and solar light
Quinclorac (QNC) is a widely used herbicide and is persistent in surface and ground waters. Its residuals and converted products are hazardous to aquatic animals, vegetation, and microbes, and it is therefore important to degrade QNC using an efficient and environmental friendly technology. In this study, the photocatalytical degradation of QNC using [(R,R)-(N,N′ -bis(3,5,3′ ,5′ -tetra-tert-butylsalicylidene)-1,2-cyclohexanediaminato] manganese(III) acetate (Mn (III) salen) and H2O2 was performed under natural sunlight irradiation and a 91% degradation rate was achieved in neutral pure water in 240 min.
4/3/2023 10:13:49 PM +00:00
Highly efficient catalytic degradation of low-density polyethylene Using a novel tungstophosphoric acid/kaolin clay composite catalyst
In order to take advantage of the Brønsted acidity of tungstophosphoric acid (TPA) and Lewis acidity of kaolin, TPA-loaded kaolin catalysts with varying percentages of TPA (10–50 wt.-%) were prepared by wet impregnation method. Fourier transform infrared spectrometer, X-ray diffractometer, Brunauer–Emmett–Teller surface area analyzer, and scanning electron microscope characterizations were performed to confirm the successful loading of TPA on kaolin. Catalytic cracking of low-density polyethylene (LDPE), by employing TPA-loaded kaolin as the catalyst, produced a higher percentage of fuel oil (liquid and gaseous hydrocarbons) with a negligible amount of semisolid wax (1.0 wt.-%).
4/3/2023 10:13:41 PM +00:00
Anticorrosion coating for magnesium alloys: Electrospun superhydrophobic polystyrene/SiO2 composite fibers
Superhydrophobic nanocomposite coatings for magnesium surfaces with remarkable corrosion resistance were fabricated by electrospinning in the presence of fluorosilane-functionalized silica (SiO2) nanoparticles. The effects of surface-modified silica (mod-SiO2) nanoparticles on the superhydrophobicity and corrosion resistance of polystyrene (PS)/mod-SiO2 fiber coatings were evaluated. The incorporation of the SiO2 nanoparticles endows PS fibers with rough surfaces exhibiting a water contact angle (WCA) of 165◦C. The surface wettability, corrosion resistance, and their relation to the inorganic content in the PS fibers and the contact angle of the composite coatings were explored.
4/3/2023 10:13:19 PM +00:00
S-substituted derivatives of 1,2,4-triazol-3-thiol as new drug candidates for type II diabetes
The therapeutic applications of 1,2,4-triazoles motivated us to synthesize some new derivatives. Two series of S -substituted derivatives (8a–8j, 12a–12i) of 5-{1-[(4-chlorophenyl)sulfonyl]-3-piperidinyl}-4-phenyl-4H -1,2,4-triazol3-thiol (6) have been synthesized and evaluated for their biological potential. Using 4-chlorobenzene sulfonyl chloride (1) and ethyl piperidine-3-carboxylate (2), ethyl 1-[(4-chlorophenyl)sulfonyl]piperidine-3-carboxylate (3) was synthesized and converted into 3,4,5-trisubstituted 1,2,4-triazole (6) through formation of the corresponding carbohydrazide (4) and hydrazinecarbothioamide (5). Compound 6 was transformed into 8a–8j by alkyl halides (7a–7j) and into 12a–12i by N-aralkyl/aryl-2-bromoacetamides (11a–11i) in an aprotic solvent.
4/3/2023 10:13:09 PM +00:00
Schiff base of isoniazid and ketoprofen: synthesis, X-ray crystallographic, spectroscopic, antioxidant, and computational studies
Ketoprofen and isoniazid together are a potential combination of a nonsteroidal antiinflammatory drug and an antitubercular medicine to treat tuberculosis and associated symptoms like fever and fatigue. The Schiff base of isoniazid with ketoprofen is synthesized in this research. Infrared spectroscopy (IR) and X-ray diffraction (XRD) analysis of the crystal packing proved the formation of the Schiff base and the existence of N-H···O hydrogen bonds between the hydrogen-bonded dimer of the Schiff base. The complete geometrical optimization of the monomer and hydrogen-bonded dimer of the Schiff base is performed utilizing M06-2X/6-31G(d,p) level theory and compared with the experimental data to optimize the molecular structure.
4/3/2023 10:12:55 PM +00:00
Enhanced electrocatalytic activity of copper phthalocyanine/multiwalled carbon nanotube composite electrode via Pt nanoparticle modification for oxygen reduction
Enhanced electrocatalytic reduction of oxygen is achieved using Pt nanoparticle-modified copper phthalocyanine-multiwalled carbon nanotube (PtNPs/CuPc-CNT) composite film on a glassy carbon electrode (PtNPs/CuPcCNT/GCE). The PtNPs/CuPc-CNT/GCE surface is characterized by scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The electrocatalytic activity of composite electrodes in the oxygen reduction reaction is investigated by cyclic voltammetry and rotating-disk electrode measurements.
4/3/2023 10:12:46 PM +00:00
Ligand binding constants of the cucurbit[7]uril predicted with molecular docking: A theoretical study
A binding stability order predicting, molecular docking based fast technique was developed for host–guest complexes. Molecular descriptors were applied to ligand molecules to make the binding energy based docking scoring functions more efficient and reach the ±0.50 log K unit theoretical precision for predictions. The goal of this work was to model complexes of cucurbit[7]uril (CB7) as a host molecule with different local anesthetics and choline and phosphonium choline molecules.
4/3/2023 10:12:36 PM +00:00
Recent advances in organ-on-a-chip technologies and future challenges: A review
The significant development in the construction of microscale cell culture platforms and the interest in bioanalytical analysis have recently resulted in the emergence of a new concept of ‘organ-on-a-chip’ systems. Organon-a-chip is a new three-dimensional (3D) in vitro microfabricated unit that contains a multichannel microfluidic cell culture. Even if many informative and useful data are obtained from animal models and in vitro assays, they are still limited for extrapolation to human systems during drug design and development. Only about 1 out of 10,000 compounds is processed in clinical trials for final approval.
4/3/2023 10:12:14 PM +00:00
Synthesis of quaternized zinc(II) and cobalt(II) phthalocyanines bearing pyridine-2-yl-ethynyl groups and their DNA binding properties
The synthesis and biological properties of tetra-substituted zinc and cobalt phthalocyanines bearing ethynylpyridine units on the periphery and their quaternized derivatives have been reported. The binding of quaternized ZnPc and CoPc (Q-ZnPc and Q-CoPc) with calf thymus DNA was investigated by UV-Vis spectrophotometric methods and thermodynamics. The mixtures of Q-ZnPc or Q-CoPc and DNA solutions were used to determine the change in the thermal melting temperature of DNA with the thermal denaturation profile. Thermodynamic parameters that show the spontaneity of the reactions between DNA and the quaternized phthalocyanines were investigated.
4/3/2023 10:12:06 PM +00:00
Physicochemical characterization of different cellulose polymorphs/graphene oxide composites and their antibacterial activity
In order to investigate the interaction of graphene oxide (GO) with different cellulose polymorphs (I and II), we synthesized cellulose (I and II)/GO composites using the sonication method. Interestingly, no new peaks were observed in the FT-IR pattern of the cellulose (I and II)/GO composites, indicating that no chemical reactions took place between GO and cellulose. The X-ray diffraction patterns of cellulose I and II/GO composites were slightly different than those observed for cellulose I and II, indicating that some physical interactions occurred between the GO and cellulose.
4/3/2023 10:11:57 PM +00:00
Adsorptive properties of mesoporous silica modified with Lewis base molecule and its application in the preconcentration of Cu(II), Co(II), and Cd(II) from aqueous media
Cocondensation and postfunctionalization methods were employed to synthesize a mesoporous silica with large surface area (795.1 ± 1.1 m2 g −1 ) modified with 4-amino-5-hydrazino-1,2,4-triazole-3-thiol, which was successfully applied to adsorb and preconcentrate Cu(II), Co(II), and Cd(II) from aqueous media. Infrared spectroscopy of the adsorbent material demonstrated N-H stretching bonds related to primary amines existing in the ligand molecule, elemental analysis revealed the presence of 0.132 mmol g −1 of nitrogen, scanning electron microscopy indicated globularly shaped particles with average size of 10 µm, and the point of zero charge was found to be 7.2. Kinetic data were applied to the pseudo-second-order model, indicating that a chemisorption mechanism is probably involved in the uptake of metal ions from aqueous solutions.
4/3/2023 10:11:45 PM +00:00
Synthesis and characterization of new thiophene–benzimidazole-based electrochromes
In the present study, two new donor–acceptor–donor-type molecules were synthesized and the electro-optical properties of the resulting monomers and their corresponding polymers were investigated. Thiophene was selected as the donor unit and cycloheptyl- and cyclooctyl- substituted benzimidazoles were used as the acceptor units. The synthesized monomers and their electrochemically obtained polymers were characterized using cyclic voltammetry and UV-Vis spectrometry. The optical band gap values of the polymers were 1.62 eV and the polymer films changed color to gray upon oxidation, while they were brick red in their neutral states.
4/3/2023 10:11:35 PM +00:00
Biological evaluation and synthesis of new pyrimidine-2(1H)-ol/-thiol derivatives derived from chalcones using the solid phase microwave method
Twenty-five new hydroxy- and methoxy-substituted 4,6-diarylpyrimidin-2(1H)-ol (20–34) and 4,6-diarylpyrimidine-2(1H)-thiol derivatives (35–44) were synthesized from the reaction of the corresponding 1,3-diaryl-2-propene-1- one compounds (1–19) with urea or thiourea using the solid-phase microwave method. All the new synthetic compounds (20–44) were evaluated with regard to their α-glucosidase activity. However, only compounds 22–25, 27, 31, 34, 35, 37, and 40 exhibited a greater inhibitory effect than standard acarbose. The IC50 values of the active compounds ranged between 2.36 and 13.34 µM. The 25 new compounds were also screened for their in vitro pancreatic lipase activity and compounds 20–27 and 35–39 were found to be active.
4/3/2023 10:11:24 PM +00:00
Removal of five cationic dyes using a resin coated with nickel/nickel boride nanoparticles
Resins coated with nickel/nickel boride nanoparticles were used to remove brilliant green, methyl violet, methylene blue, phenosafranine, and brilliant cresyl blue from water. The effects of pH, adsorbent dose, contact time, and initial dye concentration on the adsorption efficiencies were investigated. The point of zero charge for the adsorbent was pH 9.5. Isotherm studies were conducted using Langmuir, Freundlich, and Dubinin–Radushkevich models, and thermodynamic studies were also performed. Adsorption of the five dyes was found to obey the Langmuir isotherm model and was endothermic.
4/3/2023 10:11:12 PM +00:00