Tài liệu miễn phí Hoá học
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Synthesis and evaluation of catecholase activities of metal complexes of 1,4-substituted piperazine Mannich base of 4-acetamidophenol
The synthesis and characterisation including 1 H and 13 C NMR spectroscopy of a Mannich base 1,4-di-(5- acetamido-2-hydroxybenzyl)piperazine is herein reported. The Mannich reaction leading to the formation of the ligand took place at both ends of piperazine. Four metal complexes [Cu(II) and Fe(III)] including those bearing thiocyanate groups (SCN–) in N- and S-bonding modes have been studied for their abilities to mimic catecholase oxidase. All the metal complexes are catalytically active with the highest turnover rate (k cat) recorded for complex 3. The catalytic process as monitored by 1 H NMR spectroscopy (isolation of 3, 5-DTBQ) and iodometric titration revealed the formation of H2 O2 and thus implied that the mechanism of oxidation is through the formation of a semiquinolate species.
4/3/2023 10:23:36 PM +00:00
Preparation and characterization of photocatalytic TiO2/glymo nanocomposite films
The reflux method was utilized for the synthesis of 5% Sn-doped TiO2 nanopowder. Surfaces of the TiO2 particles were modified with 3-glycidoxypropyltrimethoxysilane (glymo) and glass surfaces were coated with this solution by a spin-coating process. Molar ratios of TiO2:glymo were 0.25, 0.5, 2.5, and 7.5 in the films. Nanocomposite films were cured at 130 ◦ C. Adhesions of the obtained films were classified as 5B and pencil hardness increased with the increase in the ratio of the TiO2 in the films. Film thickness decreased from 5 µm to 0.3 µm when TiO2:glymo was increased from 0.25 to 7.5.
4/3/2023 10:23:28 PM +00:00
Synthesis, sintering, electrical properties, and sodium migration pathways of new lyonsite Na2Co2(MoO4)3
A new double molybdate Na2Co2(MoO4)3 was synthesized via solid-state reaction and characterized by single-crystal X-ray diffraction (XRD). This compound is a new member of the lyonsite structure type. It crystallized in the orthorhombic system, space group Pnma with cell parameters a = 5.272(2) Å, b = 10.816(3) Å, and c = 18.064(3) Å. The structure can be described as a three-dimensional framework with hexagonal tunnels in which the Na+ cations lie. The obtained structural model is supported by charge distribution analysis and bond valence sum validation tools.
4/3/2023 10:23:14 PM +00:00
Poly L-Dopa/poly(ethylenedioxythiophene) as a novel mussel-inspired electroactive binder for environmentally friendly hybrid supercapacitors
3,4-Dihydroxy-L-phenylalanine and ethylenedioxythiophene were chemically copolymerized via an oxidative process in aqueous solution. The copolymer was used as a novel mussel-inspired electroactive binder in conjunction with a nickel-based metal organic frame work for fabrication of environmentally friendly supercapacitors. The binder, in addition to the sticking effect, contributes to electric charge storing via the redox process of catechol moieties of poly(3,4-dihydroxy-L-phenylalanine) and also the formation of a high charge-storing double layer due to the presence of poly(ethylenedioxythiophene).
4/3/2023 10:22:30 PM +00:00
Thermolytic synthesis of cobalt and cobalt sulfide nanoparticles using Cobalt(II) N∧O Schiff base complexes as single molecular precursors
Two novel N∧O-type Schiff base ligands and the corresponding Co(II) complexes are reported. Thermogravimetric analysis indicated that the complexes are potential molecular precursors for the fabrication of cobalt and cobalt-containing nanomaterials. The significant difference in the thermal decomposition profiles is recognized as an influence of structural differences on the complexes. Thus, the complexes were thermally decomposed using the melt and hot injection methods to examine the properties of the obtained cobalt and cobalt sulfide nanoparticles, respectively. The reaction parameters employed during the fabrication processes, in addition to structural differences, influenced the morphological and crystallographic phases and magnetic properties of the synthesized nanoparticles.
4/3/2023 10:21:55 PM +00:00
Phase transition of chemically synthesized FePt nanoparticles under high pressure
We present the results of a study related to phase transformation of chemically synthesized FePt nanoparticles under high pressure from face-centered cubic into face-centered tetragonal structure. As-synthesized nanoparticles are around 4.5 nm and show superparamagnetic behavior at 300 K. After annealing under 60 bar pressure of hydrogen at 400◦C for 2 h, nanoparticles exhibit strong ferromagnetic behavior with 5391 Oe coercivity. Results show that highpressure annealing lowers the decomposition temperature of the surfactants surrounding nanoparticles and partially hinders agglomeration arising from heat treatment.
4/3/2023 10:21:44 PM +00:00
Tetrahydropyridine: A promising heterocycle for pharmacologically active molecules
The tetrahydropyridine (THP) ring system has received considerable focus due to its excellent ability to act as a pharmacophore. It is recognized as a major constituent in natural alkaloids. THP derivatives have been reported for a diverse range of biological activities. Recent synthetic works contain syntheses of monosubstituted, disubstituted, trisubstituted, highly functionalized, and condensed structures. In this review, we summarize the recent literature dealing with the bioactive nature of this important heterocycle.
4/3/2023 10:21:33 PM +00:00
A sample stacking-capillary electrophoresis method for simultaneous determination of nitrate and thiocyanate ions of ultra-heat-treated milk samples
Ultra-heat-treated (UHT) cow milk is mostly consumed in Turkey. Heating milk can cause some chemical and biochemical changes that affect different components of milk. However, studies on the constituents of UHT milk are scare. In the present study, nitrate and thiocyanate contents of commercial UHT whole cow milk were determined simultaneously by sample stacking-capillary electrophoresis. The best separation of nitrate and thiocyanate ions was performed by reducing the electroosmotic flow at pH 4.0 using 30 mM formic acid and 30 mM sodium sulfate containing separation electrolyte.
4/3/2023 10:21:27 PM +00:00
Syntheses and characterizations of cyclotriphosphazenes containing a 4-oxy-1-naphthaldehyde group
The nucleophilic substitution reaction of hexachlorocyclotriphosphazene (N3P3Cl6, trimer) (1) with 4- hydroxy-1-naphthaldehyde (2) has been investigated for the first time. 4′ -Oxy-1′ -naphthaldehyde substituted mono- (3), bis- (4), and tris- (5) cyclotriphosphazenes were obtained from the nucleophilic substitution of compound 1 with 2 in a 1:2 molar ratio in the presence of Cs2CO3 in acetone at reflux. The pentakis-(6) and hexakis-substituted (7) cyclotriphosphazenes were prepared from the reaction of 1 with 2 in a 1:7 molar ratio using K2 CO3 as a proton abstractor in tetrahydrofuran at room temperature. The structures of the new compounds (3–7) were determined by elemental analysis, FT-IR, and mass and nuclear magnetic resonance (1H and 31P) spectroscopies.
4/3/2023 10:21:18 PM +00:00
Castor oil and PEG-based shape memory polyurethane films: Effect of chain extender amount on some polymer properties and performance
A series of polyurethane (PU) films were synthesized via one-shot bulk polymerization with polyethylene glycol, castor oil, hexamethylene diisocyanate, and 1,4-butanediol (BD) at three different chain extender ratios. Since it was found in our previous study that hard segment content is more effective on shape memory property than soft segment length (Bonfil, M., Sirkecioglu, A., Bingol-Ozakpinar, O., Uras, F., Güner, F. S. J. Appl. Polym. Sci. 2014, 131, 1–12), in this study the effects of BD amount on some physical properties, thermal properties, and shape memory performance of the films were investigated.
4/3/2023 10:20:52 PM +00:00
Use of calcined layered double hydroxide [Zn2-Al-CO3] for removal of textile dye acid green 1 from wastewater: Kinetic, equilibrium, comparative, and recycling studies
In the present study, calcined layered double hydroxides (CLDHs) were obtained by heating [Zn2-Al-CO3 ] at 500◦C. The adsorption of the textile dye acid green 1 (AG1) by CLDH was carried out at different pH levels, adsorbent–adsorbate contact times, and AG1/CLDH mass ratios. Equilibrium at room temperature was reached after 24 h, which was confirmed by the kinetic modeling of the experimental data by the pseudo-second-order model. The adsorption is described by a Langmuir-type isotherm. The comparative study of adsorption isotherms in calcined and uncalcined phases reveals that the former could be a good candidate for trapping such pollutants.
4/3/2023 10:20:45 PM +00:00
The design and synthesis of a photo-controlled, peptide-based potential drug carrier
Our focus in this study is on the design and synthesis of a light-responsive peptide-based nanocarrier in order to develop effective and biocompatible drug delivery systems. The synthesized nanocarrier is basically composed of peptide amphiphiles comprising a micelle forming a Pro-Pro-Pro-Lys-Lys-Lys peptide sequence with an attached anthracene fluorophore. Anthracene containing an inner core of the micelle can serve as a storage site for poorly watersoluble drugs.
4/3/2023 10:20:33 PM +00:00
Differential pulse voltammetric determination of dopamine using Pd nanoparticles deposited on (3-aminopropyl)triethoxysilane functionalized CeO2 nanoparticles
In this study, a novel and effective electrochemical sensor for determination of dopamine (DA) was successfully developed by the modification of a glassy carbon electrode (GCE) using Pd nanoparticles deposited on (3- aminopropyl)triethoxysilane functionalized nanoceria (Pd@CeO2 -APTES) and nafion used as a protective membrane. The synthesized nanocomposites were evaluated using X-ray diffraction, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. Moreover, the electrochemical properties of the modified electrodes were investigated using cyclic voltammetry, electrochemical impedance voltammetry, and differential pulse voltammetry (DPV).
4/3/2023 10:20:14 PM +00:00
Synthesis, molecular docking, and pharmacological evaluation of halobenzodithiophene derivatives against alpha-glucosidase, urease, and free radical production
Benzodithiophenes are heterocyclic compounds that have various medicinal and industrial applications. In the present study, halobenzodithiophene, the simplest benzofused thiophene, and its derivatives were synthesized and evaluated against alpha-glucosidase, urease, and free radical production. In the alpha-glucosidase inhibition assay, compound 2,2-bisbenzothiophne (1) exhibited potent activity with IC50 = 135 ± 0.51 µM, while its derivative 2,7-bis(butoxycarbonyl)-3,6-dichlorobenzo[1,2- b ;6,5- b ’]dithiophene (2) exhibited promising inhibition with IC50 = 263 ± 0.32 µM. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, compound 2 exhibited promising activity with IC50 = 33 ± 0.42 µM, while compound 1 showed moderate inhibition in the urease inhibition assay.
4/3/2023 10:20:00 PM +00:00
Synthesis, characterization, and evaluation of antioxidant activity of new γ- and δ-imino esters
New Schiff bases were synthesized by condensation of methyl-5-(furan-2-yl)-5-oxopentanoate, methyl-4- (furan-2-yl)-4-oxobutanoate, methyl-5-(thiophene-2-yl)-5-oxopentanoate, and methyl-4-(thiophene-2-yl)-4-oxobutanoate with p-anisidine and n-butylamine. The structures of these synthesized compounds were clarified on the basis of elemental analysis, IR, 1H NMR, 13C NMR, and GC-MS spectroscopic techniques. In addition, antioxidant activity of the synthesized compounds was evaluated on the basis of DPPH radical.
4/3/2023 10:19:48 PM +00:00
Synthesis, characterization, and evaluation of toxicity of quaternary ammonium chlorides of glucose-based ester
This study presents the synthesis of glucose-based surfactants including quaternary ammonium salts. Their surface properties and influence on the soil environment were investigated. The synthesized quaternary ammonium chlorides of glucose-based ester exhibited good surface tension reduction properties and formed stable foam in contact with water. The results showed that quaternary ester ammonium salts affect the activation of metals (nickel and cadmium) from the soil matrix after their introduction into the soil environment. This phenomenon can increase the bioavailability of these metals.
4/3/2023 10:19:34 PM +00:00
The synthesis of new 3,4-(bisaryl)-1,8-naphthalimide and 2,3-(bisaryl)-7H-benzimidazo[2,1-a]benzo[d]isoquinolin-7-one compounds and an investigation of their photochromic properties
Three new photochromic compounds, 3-(2,5-dimethyl-3-thienyl)-4-(2-phenyl-5-methyl-4-thiazolyl)-1,8-naphthalimide (1-O), 2,3-bis(2-phenyl-5-methyl-4-thiazolyl)-7H -benzimidazo[2,1-a]benzo[de]isoquinolin-7-one (2-O), and 2,5- dimethyl-3-thienyl)-7H -benzimidazo[2,1-a]benzo[de]isoquinolin-7-one (3-O), were synthesized and their photochromic properties were studied. Compound 1-O was synthesized by two consecutive Suzuki coupling reactions using 2,5- dimethylthiophene-3-boronic acid and 5-methyl-2-phenylthiazole-4-boronic acid. Photochromic compounds 2-O and 3-O were prepared by multistep reactions starting with 3-iodo-4-bromo-1,8-naphthalic anhydride and 2,5-dimethylthiophene3-boronic acid or 2-phenyl-5-methylthiazole-4-boronic acid.
4/3/2023 10:19:27 PM +00:00
New N -4 piperazinyl derivatives of norfloxacin: Design, synthesis, and correlation of calculated physicochemical parameters with antibacterial activity
A group of N−4 piperazinyl derivatives of norfloxacin was synthesized and identified by different spectroscopic techniques. The N−4 piperazinyl substituent in target compounds 2a–2k, 3a–3c, and 4a and 4b was designed to have different electronic, steric, and physicochemical properties. The antibacterial activity of the newly synthesized compounds was evaluated against Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus strains using norfloxacin as a reference. Results showed that most of the tested compounds had higher activity against E. coli and K. pneumoniae than norfloxacin, whereas only five derivatives were more active against P. aeruginosa.
4/3/2023 10:19:18 PM +00:00
Development of a nanoscale-based optical chemical sensor for the detection of NO radical
Nitric oxide is one of the most important biochemical parameters in biological processes; it is also known as carcinogenic. There is need for the design of stable and durable solid phase nitric oxide sensors. In this study, we immobilized the nitric oxide sensitive molecules pyrene, tris(2,2’-bipyrdyl)dichlororuthenium(II) hexahydrate (Ru(bipy) 2+ 3 ), and magnesium phthalocyanine (Mg-Pc) for the first time in polymeric or glassy matrices. We applied silver nanoparticles and ionic liquids in the fabrication process of polymeric electrospun fibers and thin films.
4/3/2023 10:19:03 PM +00:00
A rapid and sensitive spectrofluorometric method for the determination of Au(III) based on fluorescence quenching of a 1,3,5-triphenyl-2-pyrazoline
A simple, rapid, sensitive, and low-cost spectrofluorometric method was developed for the determination of Au(III) using 5-(2,3-dimethoxyphenyl)-3-(4-methoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (L) in ethanol/water. The method is based on the change in the fluorescence intensity at 464 nm after excitation at 355 nm as a result of the reaction between the ligand and Au(III). The fluorescent emission of ligand at 464 nm decreased with the increasing of Au(III) concentration. The ligand concentration, pH effect, response time, and effect of foreign ions were determined.
4/3/2023 10:18:52 PM +00:00
Ion-pair based liquid–liquid extraction of gold(III) from malonate media using 2-octylaminopyridine as an extractant: Analysis of alloys, minerals, and drug samples
Liquid–liquid extraction of Au(III) from aqueous sodium malonate medium using 2-octylaminopyridine (2-OAP) as an extractant in xylene was achieved. The current work explored the influence of several experimental parameters such as pH, weak acid concentration, extractant concentration, equilibrium time, stripping agents, and aqueous:organic volume ratio on the extraction of Au(III). The experimental results showed that the Au(III) was quantitatively extracted to about 99.5% by 0.05 M 2-OAP in 0.05 M malonate at 5.0 pH. Ammonia solution was used to strip the gold-loaded organic phase and about 99.5% of Au(III) was reversibly extracted into the aqueous phase.
4/3/2023 10:18:42 PM +00:00
Solid-phase extraction method for preconcentration of cadmium and lead in environmental samples using multiwalled carbon nanotubes
A new sensitive and accurate solid-phase extraction method for preconcentration of trace amounts of cadmium and lead in various environmental samples prior to flame atomic absorption spectrometry determination has been developed. The proposed method is based on the utilization of multiwalled carbon nanotubes in combination with 5-benzyl-4-[-chlororbenzylidene amine]-4H-1,2,4-triazole-3-thiol (BCBATT) as a solid-phase sorbent with the aid of ultrasonication. The effect of the preconcentration parameters was investigated.
4/3/2023 10:18:31 PM +00:00
A novel one-pot and rapid synthesis of polyfunctionalized benzo[a]pyrimido[5’,4’:5,6] pyrido[2,3-c]phenazine derivatives under microwave irradiation
A one-pot, environmentally friendly, and efficient protocol for the synthesis of novel polyfunctionalized benzo[a]pyrimido[5’,4’:5,6]pyrido[2,3-c ]phenazine derivatives has been reported by a one-pot, four-component sequential reaction between 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines, benzaldehydes, and 6-amino-1,3-dimethyluracil in the presence of p-TSA as a nontoxic, inexpensive, ecofriendly, and efficacious solid acid catalyst. Two C-C bonds, two C=N bonds, and one C-N bond, as well as two new rings, were formed in this reaction.
4/3/2023 10:18:23 PM +00:00
Voltammetric determination of phenmedipham herbicide using a multiwalled carbon nanotube paste electrode
Phenmedipham is an herbicide used especially in the sugar beet harvest to fight against broad-leaved weeds and studies of its voltammetric behavior and detection have not been done before. The superior properties of carbon nanotubes such as electrical conductivity, mechanical strength, and wide potential ranges make them attractive for chemical sensors and the phenmedipham compound gave an oxidation peak at +1320 mV (vs. Ag/AgCl) on the nanostructured multiwalled carbon nanotube paste electrode. Square wave voltammetric measurements recorded for phenmedipham showed that the peak current increased linearly between 0.02 and 2.0 mg/L with a regression coefficient of r = 0.9989, and the limit of detection and limit of quantification were calculated as 6.96 µg/L and 23.2 µg/L, respectively.
4/3/2023 10:18:12 PM +00:00
Host/guest inclusion system of surfactants with β -cyclodextrin as a viable catalyst for one-pot synthesis of mono- and bis (indolyl)methylmalononitriles in H2O
In this study, encapsulation processes of cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) monomers into the cavity of β -cyclodextrin (β -CD) were applied to synthesize mono- and bis (indolyl)methylmalononitrile derivatives by a one-pot three-component reaction of an aldehyde, malononitrile, and indole in an aqueous solution. These two inclusion complexes proved to be superior to CTAB or SDS individually, as cationic or anionic surfactants, respectively, for accessing high yields of pure products within shorter reaction times. In addition, simple isolation of products and mild reaction conditions are the other advantages of this green procedure.
4/3/2023 10:18:05 PM +00:00
New triplet silylenes M–Si–M′–X along with some unusual cyclic forms (M = Li, Na, and K; M′ = Be, Mg, and Ca; X = F, Cl, and Br)
Comparison of 54 M–Si–M′–X species is carried out using quantum mechanical ab initio and DFT computations at B3LYP/6-311++G**, QCISD(T)/6-311++G**, and CCSD(T)/6-311++G** levels of theory (M = Li, Na, K; M′ = Be, Mg, Ca, and X = F, Cl, Br). All triplet species with M = K appear more linear than their corresponding ones with Li and Na. The electronegativity reactivity descriptor for each halogen (X = F, Cl, Br) is used as a tool to evaluate the interrelated properties of these silylenes. Stability, assumed as singlet–triplet energy difference (∆ES−T) for each series depends on the substituent’s electropositivity, analyzed by applying appropriate isodesmic reactions.
4/3/2023 10:17:53 PM +00:00
One-step potentiostatic codeposition and electrochemical studies of poly(1-pyrenyl)-2,5-di(2-thienyl)pyrrole-co-pyrrole) film for electrochemical supercapacitors
In this paper, we report a simple, low-cost, and environmentally friendly electrochemical method to obtain a novel copolymer consisting of 1-pyrenyl-2,5-di(2-thienyl)pyrrole and pyrrole on a pencil graphite electrode (PGE). Poly(1-pyrenyl)-2,5-di(2-thienyl)pyrrole-co-pyrrole) that is P(PyrPy-co-Py) film was prepared by one-step potentiostatic codeposition in an ethanol solution containing PyrPy and Py monomers for supercapacitor applications. The electrodeposition of homopolymer and copolymer modified electrodes was carried out on the surface of the PGE via chronocoulometry. For comparison, P(Py)/PGE and P(PyrPy)/PGE were also electrochemically synthesized under the same reaction conditions.
4/3/2023 10:17:45 PM +00:00
Facile synthesis of IrO2 nanoclusters and their application as catalysts in the degradation of azo dyes
A robust synthesis of iridium oxide (IrO2) nanoclusters using methanol as a reducing agent via the chemical reduction method is reported in this article. Polyvinylpyrrolidone (PVP) and polyoxyethylene(23) lauryl ether (POLE) were used as stabilizers. The formation of IrO2 nanoclusters was confirmed by the appearance of new absorption peak at 230 nm in UV-vis spectra. XRD and TEM were used to determine the degree of crystallinity and size of nanoclusters, respectively. Further characterization studies were carried out by FT-IR spectroscopy to investigate the coordination between IrO2 nanoclusters and stabilizers.
4/3/2023 10:17:35 PM +00:00
Synthesis of novel SN38-aspirin prodrugs for the treatment of hepatocellular carcinoma
Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is a leading cause of cancer-related death worldwide. However, there is no effective chemotherapeutic treatment for HCC and its prognosis remains poor. Consequently, it is urgent to find an efficient antitumor agent to treat HCC. In this study, 7-ethyl-10- hydroxycamptothecin (SN38), the bioactive metabolite of the anticancer drug irinotecan (CPT-11), which is 100–1000 times more potent than CPT-11, was coupled with aspirin to give 4 prodrugs. Their structures were characterized by 1H NMR and elemental analysis.
4/3/2023 10:17:24 PM +00:00
Removal of toxic metals from canola oil by newly synthesized calixarene-based resin
This study describes the synthesis, characterization, and application of a new p−sulfonatocalix[4]arenebased silica resin (calix-resin 5) for the extraction of selected metals, namely Pb, Cd, Co, Ni, Cu and Fe, from canola oil. Synthesis, morphology, purity, and elemental composition of calix-resin 5 were analyzed by FT-IR spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The metal extraction efficiency of calix-resin 5 was evaluated through the batch-wise method with a flame and graphite furnace atomic absorption spectrometer following the wet acid digestion procedure.
4/3/2023 10:17:14 PM +00:00