Tài liệu miễn phí Hoá học
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Targeting human telomeric DNA with azacyanines
Small molecules targeting telomeric DNA or its interactions with telomerase have been an active area of cancer research. In the present study, we investigated the interactions of six benzimidazole compounds, called azacyanines, differing from each other in alkyl chain length and branching in the benzimidazole ring (azamethyl, azaethyl, azapropyl, azaisopropyl, azabutyl, and azaisobutyl) with human telomeric DNA (tel24) in 1:1 and 1:6 ratio (tel24:azacyanine) using UV-Vis, circular dichroism (CD), and fluorescence spectroscopy. All the compounds were binding to tel24 as indicated by the formation of the weak induced CD band between 320 nm and 360 nm.
4/3/2023 10:47:42 PM +00:00
Antioxidant properties of water-soluble phthalocyanines containing quinoline 5-sulfonic acid groups
In the present study, the antioxidant properties of peripherally and nonperipherally water-soluble tetra (quinoline 5-sulfonic acid) substituted metal-free (1, 2), Zn(II) (3, 4), Co(II) (5, 6), and Mn(III)Cl (7, 8) phthalocyanine (Pc) derivatives were reported. In order to determine the antioxidant properties of the Pc compounds, three different commonly known antioxidant methods were used: DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging, ferrous ion chelating, and reducing power assays. Compound 6 showed the best DPPH activity among the other tested compounds except for the standards. The ferrous ion chelating IC50 value of compound 7 was nearly as good as that of the EDTA standard.
4/3/2023 10:47:33 PM +00:00
Peripherally 1,2-dinaphthyl ethanediol substituted phthalocyanine complexes: Synthesis, characterization, aggregation, and application in benzyl alcohol oxidation at room temperature
In this study, the synthesis of a novel 1,2-dinaphthyl ethanediol substituted phthalonitrile (2) together with tetra-substituted zinc(II) phthalocyanine (Pc) (3) and cobalt(II) Pc (4) bearing 1,2-dinaphthyl ethanediol at peripheral positions was described. The aggregation behaviors of metallophthalocyanines 3 and 4 in solution were investigated by carrying out Beer–Lambert experiments at different concentrations. In addition, the catalytic activity of new cobalt(II) Pc 4 was investigated for benzyl alcohol oxidation. Benzyl alcohol was converted to benzaldehyde using cobalt(II) Pc 4 as a catalyst by a conversion of 99% with selectivity of 100% at room temperature in 1 h.
4/3/2023 10:47:20 PM +00:00
Synthesis and spectroscopic characterization of new phthalocyanine derivatives: application as photocatalysts for the degradation of Orange G
New derivatives of 2(3),9(10),16(17),23(24)-tetrakis-(6-methylpyridin-2-yloxy)phthalocyanine (Pc) (2b, 2c, and 2d) were synthesized and their structures were characterized by elemental analysis, IR, 1 H NMR, and high-resolution mass spectrometry. The spectral results were in line with the proposed structures. The photodegradation of Orange G (OG) dye in DMSO by the Pc derivatives was investigated. The compounds showed relatively high photodegradation rates that increased with increasing size of the central atoms. The Pc photodegradation rates showed fair correlation with the singlet oxygen generation efficiencies (Φ∆). The observed rate constants were higher than the values already reported for other Pcs in the literature for the photodegradation of OG in aqueous media.
4/3/2023 10:47:05 PM +00:00
Hydrogen storage in formic acid as a renewable energy source using heterogeneous catalysis
One of the most vital chemicals, which is not only found naturally but can also be synthesized in the laboratory, is formic acid (FA). FA is a key byproduct of several second-generation biorefinery processes as well, and it is used in several pharmaceutical and industrial applications. Recently, another significant use of FA that is taking the lead is as a form of fuel. This could either involve reformation, as a possible form of chemical hydrogen storage, or be done without reformation in the form of FA fuel cells, in particular because FA fuel cells are much more effective than other proton-exchange membrane fuel cells. Therefore, FA is a highly useful fuel for applications such as vehicles and portable devices.
4/3/2023 10:46:57 PM +00:00
Sensitive biological detection based on Langmuir–Blodgett films prepared from diluted silica suspensions
Self-assembled three-dimensional (3-D) colloidal crystals have been extensively utilized in nanolithography for fabricating a wide spectrum of functional periodic nanostructures for important technological applications. Here a simple and versatile way is reported using silica colloids to prepare close-packed particle multilayers by the Langmuir– Blodgett technique to create highly ordered 3-D colloidal crystals with unusual nanoarrays on a large variety of substrates. Successive deposition of monolayers using amphiphilic molecules in this approach allows control of the layer thickness, particle size, and especially packing structure of them in each layer.
4/3/2023 10:46:50 PM +00:00
Alpha-pyrone glycosides from Scutellaria salviifolia Benth
Scutellaria salviifolia Benth. is an endemic species growing in Turkey that belongs to the family Lamiaceae. As a result of a phytochemical study on the aerial parts of S. salviifolia Benth., two new and 10 known compounds were isolated from the aqueous fraction of methanolic extract. The new compounds are methyl-α-pyrone glucosides, 3,4-dihydroxy-6-methylpyran-2-one 3-O-β -glucopyranoside (=scusalvioside A, 1), and 3,4-dihydroxy-6-methylpyran2-one 3-O-β -(6′ -O-E -caffeoyl) glucopyranoside (=scusalvioside B, 2) with new skeletal structures. Along with them, 3 phloroglucinol glucosides [phlorin (3), tadehaginoside (4), and 6′′ -O-Z -p-coumaroyl phloroglucinol-1-O-β - glucopyranoside (5)], 6 flavonoids [apigenin (6), apigenin 5-O-β -glucopyranoside (7), isoschaftoside (8), luteolin 7- O-β -glucuronide (9), luteolin 4′ -O-β -glucopyranoside (10), and hispidulin (11)], and one phenylethanoid glycoside [martynoside (12)] were also isolated as known compounds.
4/3/2023 10:46:42 PM +00:00
Bisbenzoxazole derivatives had an antiinflammatory effect on in vitro stimulated macrophages
protect endangered tissueBenzoxazoles are DNA base bioisosteres and studies suggest that their derivatives have antiproliferative activities. Based on their antiproliferative activities they have been mostly studied as new generation anticancer drugs. In our study we exploited their antiproliferative effect, aiming to delineate bisbenzoxazole derivatives’ (RHE 231 and RHE 238) potential antiinflammatory effect on mouse macrophages that are activated in vitro through danger signal LPS stimulation. RAW 267.4 mammalian macrophages were activated in the presence of our derivatives with or without danger mimic E. coli derived LPS. We present data that support the strong antiinflammatory activity of the bisbenzoxazole derivatives RHE 231 and RHE 238 on stimulated mammalian macrophages.
4/3/2023 10:46:35 PM +00:00
Enhanced uptake capacities and isosteric heats of CO2 and CH4 adsorption on spent coffee ground activated carbons loaded with metal ions
Low-cost activated carbon (AC) samples obtained from waste coffee grounds were used for CO2 and CH4 adsorption. ACs were prepared by chemical activation and carbonized at three different temperatures. AC carbonized at 800◦C showed a relatively high surface area (582.92 m2 g−1) and high adsorption capacities of 2.6 mmol g−1 and 1.1 mmol g−1 at 25◦C for CO2 and CH4, respectively. Adsorbent samples were prepared by loading of Fe3+ metal ions onto ACs and their adsorption capacities were compared with those of nonloaded ACs. As expected, the loading of Fe3+ metal ions increased the adsorption capacities at all temperatures and the adsorption capacity of Fe3+ -loaded AC carbonized at 800◦C was 3.1 mmol g−1 for CO2 and 1.2 mmol g−1 for CH4 at 25◦C. The isosteric heats of adsorption were calculated at 0–35◦C with the range of 20–35 kJ mol−1 and 18–23 kJ mol−1 for CO2 and CH4, respectively. According to our findings, bio-based ACs can be used as an effective and alternative adsorbent for capturing different gas molecules.
4/3/2023 10:46:21 PM +00:00
A theoretical investigation on the activation of small molecules by a disilenide: A DFT prediction
Herein, we proposed several mechanistic scenarios for activation of small molecules (NH3, CO2, CS2, H2, CH4, N2, and N2O) by a disilicon analogue of a vinyl anion (1H) using density functional theory (DFT) calculations. The DFT results established that all the possible reactions to yield a variety of potential products have an exergonic nature except for the activation of N2 with the obtained overall energy of ∆G = 33.6 kcal mol−1. Moreover, the highest exergonic character was ∆G = −95.8 kcal mol−1 for N2O. Therefore, the findings reveal that 1H can be considered a suitable candidate for activation of NH3, CO2, CS2, H2, CH4, and N2O under metal-free conditions.
4/3/2023 10:46:10 PM +00:00
Parameterization, kinetics, and adsorption isotherm of electrocoagulation process of bromothymol blue in aqueous medium using aluminum electrodes
The removal of bromothymol blue (BTB) from aqueous solution was studied by electrocoagulation (EC) technique using aluminum electrodes. The various experimental conditions known to influence the EC process were parameterized, including the effects of temperature, concentration, current density, pH, and treatment time. The results obtained have shown that optimum removal efficiency of 99.9% was realized at a current density of 20 mA/cm2 and pH of 4.7. The adsorption process showed a pseudo-first-order kinetic model as the best fit to the EC data.
4/3/2023 10:46:02 PM +00:00
Synthesis of tetrakis bromine terminated phthalocyanine and its methyl methacrylate polymers via ATRP
A phthalocyanine (Pc) initiator, tetrakis(2-bromopropyloxyester)ethylthiophthalocyaninatozinc(II) (ZnPcBr), was prepared and successfully applied to atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) for the first time. Bromine end groups of the synthesized Pc took part in the initiation of the MMA chain growth. Polymerization was demonstrated by monomodal molecular weight distribution of the synthesized polymers and their increasing molecular weight behavior with reaction time. UV-Vis absorption, fluorescence, and transmittance properties of the polymers were also examined. The results indicate that the ZnPc-Br-based initiator is potentially applicable in ATRP applied to MMA in order to obtain and develop functional acrylic materials.
4/3/2023 10:45:54 PM +00:00
Synthesis, characterization, and nonlinear optical properties of some new series of S-(5-aryl-1,3,4-oxadiazol-2-yl) 2-chloroethanethioate derivatives
In the present investigation, some novel S-(5-aryl-1,3,4-oxadiazol-2-yl)2-chloroethanethioate (3a–3e) derivatives were synthesized and their impact on optical properties was studied. They have also been characterized by elemental analysis and various spectroscopic methods including FTIR, 1H NMR, 13C NMR, and UV-Vis techniques. The nonlinear refractive indexes of 3a–3e were also measured in dichloromethane via Z-scan method using a continuous wave diode-pumped laser at 532 nm wavelength. The nonlinear refractive coefficient of compounds was obtained from 1011 m2/W order.
4/3/2023 10:45:47 PM +00:00
Gas sensing with hexafluoroisopropanol substituted phthalocyanines and vic-dioximes: A comparative study
Phthalocyanines (Pcs) are established sensitive materials for chemical gas sensors due to their superb sensing characteristics and the achievable manifold in their analyte interaction properties. Their sorption properties are determined by the metal ion center and substituents attached to the periphery of the ring system. Similarly, vic-dioximes can be modified in their sorption properties and employed as sensitive materials. In this work, a nickel Pc and various vic-dioximes functionalized with the same hexafluoroisopropanol moiety are assessed and compared in their gas-sensing properties using the quartz crystal microbalance for the first time.
4/3/2023 10:45:36 PM +00:00
Determination of triacylglycerols and fatty acid composition of Chilopsis linearis seed oil by reverse-phase high-performance liquid chromatography
In the present work, the compositions of the 27 triacylglycerols (TAGs) as well as fatty acid composition of Chilopsis linearis seed oil were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) with diode array and mass spectrometric detections. It was shown that the main conjugated acid in the seed oil is a catalpic acid, (9E,11E,13Z)-octadeca-9,11,13-trienoic acid, while two unusual fatty acids have the parameters satisfying the literature data for (10E,12E)-octadeca-10,12-dienoic and (9E,12E)-octadeca-9,12-dienoic acids.
4/3/2023 10:45:29 PM +00:00
Protonation behavior of dextran amino acid esters
Dextran esters of different amino acids (glycine, β-alanine, L-ornithine, L-lysine) are investigated regarding their pKa values by potentiometric titration. The pKa values of the dextran derivatives are generally dependent on the position of the amino group in relation to the ester group, i.e. the nearer they are located in the molecule, the lower the resulting pKa values are, L-ornithine ester being the exception. An influence of the polymer backbone is ruled out. Stability against hydrolysis at different pH values and over longer periods at constant pH value is measured by potentiometric and polyelectrolyte titration.
4/3/2023 10:45:15 PM +00:00
Methyl-substituted 2-aminothiazole–based cobalt(II) and silver(I) complexes: Synthesis, X-ray structures, and biological activities
2-Aminothiazole derivatives bear three nucleophilic centers, i.e. endocyclic N, exocyclic NH2 , and S atom in the ring system. In addition to these centers there are π -electrons in the ring system which can also expectedly be involved in some sort of coordination. To the best of our knowledge the solid state coordination chemistry of such ligands has not been fully presented in the literature. These ligands (2-amino-4-methylthiazole and 2-amino5-methylthiazole) were coupled with CoCl 2 under aerobic conditions to form tetrahedral complexes, bis(2-amino-4- methylthiazole)dichlorocobalt(II) (1) and bis(2-amino-5-methylthiazole)dichlorocobalt(II) (2). Reaction of 2-amino5-methylthiazole with AgNO3 led to an expected two-coordinated, bis(2-amino-5-methylthiazole)silver(I) nitrate (3) as crystalline material.
4/3/2023 10:45:06 PM +00:00
Determination of N-acetylcysteine in the presence of ciprofloxacin or levofloxacin in microparticulate dry powder inhalers
A fast and easy method was validated for simultaneous determination of ciprofloxacin hydrochloride monohydrate (CP), levofloxacin hemihydrate (LV), and N-acetylcysteine (NAC) in samples. The analysis was performed on a C18 column (250 × 4.6mm, 5µm) (Inertsil ODS-3V) using an isocratic elution method with a mobile phase composed of 25mM KH2PO4 (pH 3.0) and methanol (72:28, v/v) at a flow rate of 1mL/min. UV detection was performed at 214nm for NAC and 293nm for CP and LV. The method was validated for linearity, accuracy, precision (repeatability and reproducibility), specificity, sensitivity, and stability.
4/3/2023 10:45:00 PM +00:00
Electrochemical oxidation of curcuminoids: An experimental and computational investigation
Curcuminoids, reported to have important biological properties, such as antioxidant, anti-Alzheimer, and antidiabetic properties, comprise curcumin (CRM; 1,7-bis [4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) and its derivatives demethoxycurcumin (DMC; (E,6E)-1-(3,4-dimethoxy-cyclohexyl)-7-(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5- dione) and bisdemethoxycurcumin (BDMC; 1,7-bis[4-hydroxyphenyl]-1,6-heptadiene-3,5-dione). Their electrochemical oxidations are thoroughly explored by applying cyclic and differential pulse voltammetric techniques.
4/3/2023 10:44:41 PM +00:00
Qualitative and quantitative determination of the effective components of the plants in different herbal slimming products in Turkey by HPLC
Obesity is a serious disease that can be due to genetic and environmental reasons and is defined by the World Health Organization as abnormal or excessive fat accumulation that may impair health. There is an increasing trend towards herbal slimming products in obesity treatment. The quality control analysis of these products is important for public health. In this study, new, simple, and sensitive high performance liquid chromatography methods were developed for qualitative and quantitative determination of arbutin, hydroquinone, ursolic acid, chlorogenic acid, epigallocatechin gallate, epigallocatechin, epicatechin gallate, and catechin in eleven herbal slimming products in Turkey containing Camellia sinensis, Ilex paraguariensis, and Calluna vulgaris.
4/3/2023 10:44:29 PM +00:00
Comparative study on physicochemical and mechanical characterization of new nanocarbon-based hydroxyapatite nanocomposites
This study evaluated the effect of different additives such as nanocarbon compounds (0.5, 1.0, and 2.0 wt.%) with different morphologies and gelatin (Gel) (10 wt.%) on the mechanical properties of hydroxyapatite (Hap)- based nanocomposites (NCs). The NCs were prepared using the innovation process “SmartBox” based on the Internet of things (IoT), which provides process control and reproducibility, and they were characterized by X-ray diffraction, particle size distribution, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermal analysis.
4/3/2023 10:44:12 PM +00:00
Sustainable process for the production of symmetrical dibasic acid ester-based thermal energy storage materials from lipids
Oleochemical-based long-chain diesters are potential organic phase change materials convenient for thermal energy storage. The development of efficient and green methods is an important requirement for the preparation of these environmentally friendly compounds, which also are finding wide industrial application. Thus, in the present work, a series of dibasic acid esters were synthesized through ionic liquid catalyzed scalable chemical esterification or transesterification reactions in a solvent-free medium.
4/3/2023 10:44:01 PM +00:00
Effect of Brij 35 and saponin surfactants on adsorption of diethylstilbestrol as an emerging estrogenic contaminant by clinoptilolite in batch and fixed-bed column experiments
In this study, natural clinoptilolite was modified by saponin and Brij 35 surfactants to remove diethylstilbestrol (DES) from wastewater in batch and continuous systems. The optimum pH, amount of adsorbent, contact time, and temperature were 11, 10 g/L, 12 h, and 35°C, respectively, for the process. The equilibrium data agreed well with the Langmuir isotherm for natural clinoptilolite (NC), natural clinoptilolite modified by Brij 35 (NC-Brij), and natural clinoptilolite modified by saponin surfactants (NC-saponin) compared to other isotherms. The maximum adsorption capacities resulting from the Langmuir isotherm for NC, NC-Brij, and NC-saponin were 8.012, 23.64, and 39.525 mg/g, respectively.
4/3/2023 10:43:53 PM +00:00
Tribological behavior and quantum chemical calculations of protic ionic liquids: synthesis, spectroscopic, and thermal properties
Protic ionic liquids (PILs) were synthesized through a stoichiometric neutralization reaction between 2,2′ - (ethylenedioxy)-bis(ethylamine) { Edbea} and various acids (formic, acetic, boric, decanoic, and gentisic acid). The PILs were characterized by elemental analyses, FTIR, 1 H and 13 C NMR spectroscopy, and thermogravimetric analysis. All the PILs except PIL3 were liquid at room temperature. The viscosity of the PILs (PIL1, 2, 4, 5) was measured using a cone-and-plate viscometer at ambient temperature. Quantum chemical calculations were used to explain the cation/anion ratio in the PILs.
4/3/2023 10:43:39 PM +00:00
Improvement of the mechanical and thermal properties of polyester nonwoven fabrics by PTFE coating
Polyester (polyethylene terephthalate) is one of the most widely used polymers in textiles. Despite all the advantages of this polymer, its low thermal resistance limits its use in filters and protective textiles. On the other hand, polyester nonwovens are used in many products as wipes, filters, and padding. The surface properties of polyester nonwovens are often not perfect for a specific application and need to be modified. Different ways, including coating, have been developed to modify their surface properties. Therefore, in the present study attempts were made to investigate the improvement of the thermal resistance of a polyester nonwoven by coating.
4/3/2023 10:43:31 PM +00:00
Improving the mechanical and thermal properties of chlorinated poly(vinyl chloride) by incorporating modified CaCO3 nanoparticles as a filler
Chlorinated poly(vinyl chloride) (CPVC)/calcium carbonate nanocomposites were successfully prepared by the incorporation of calcium carbonate (CaCO3) nanoparticles into the CPVC matrix. The compatibility between the two phases was obtained by surface modification of the CaCO3 nanoparticles with stearic acid, leading to improved material performance. The effects of the addition of different amounts of CaCO3 nanoparticles to the CPVC on the thermal, mechanical, and morphological characteristics of the CPVC/CaCO3 nanocomposites were investigated. The thermal stability of the CPVC/CaCO3 nanocomposites was evaluated by thermogravimetric analysis and differential scanning calorimetry.
4/3/2023 10:43:15 PM +00:00
Effect of Fe substitution on the partial oxidation of methane to syngas over La0.7Sr0.3Co1−yFeyO3−δ perovskites
In this research, a series of La0.7Sr0.3Co1−yFeyO3−δ (y = 0.0–0.4) was successfully synthesized by a solidstate reaction method and syngas production studies were performed using gas chromatography. Thermogravimetric analysis characterized the concentration of Fe3+, which gave a low H2/CO ratio over La0.7Sr0.3Co1−yFeyO3−δ without the presence of molecular oxygen. All samples possessed a purely rhombohedral structure. The incorporation of more Fe increased the lattice parameter and changed XRD peaks of the La1−xSrxCo0.8Fe0.2O3 from sharp and single to double.
4/3/2023 10:43:04 PM +00:00
Effect of crosslinking patterns on the properties of conjugated microporous polymers
Syntheses and detailed spectroscopic characterizations of two similar conjugated microporous polymers formed by A4 + B2 and A2 + B3 type functional monomers via Sonogashira–Hagihara polycondensation are presented in this report. The two porous polymeric networks possess mono-, di-, and tri- (1-, 1,4-, and 1,3,5-, respectively) substituted benzene rings and fused thiophenic moieties (dithienothiophenes). Because of the different conjugation patterns, their solid state nuclear magnetic resonance, infrared, and ultraviolet/visible light absorption analyses indicated significant differences.
4/3/2023 10:42:52 PM +00:00
Synthesis and antimicrobial activity of 1-(benzo[b]thiophen-4-yl)-4-(2-(oxo, hydroxyl, and fluoro)-2-phenylethyl)piperazine and 1-(benzo[d]isothiazole-3-yl)-4-(2-(oxo, hydroxy, and fluoro)-2-phenylethyl)piperazine derivatives
Twenty-two compounds in a series of 1-(benzo[ b ]thiophen-4-yl)-4-(2-(oxo, hydroxy, and fluoro)-2-phenylethyl) piperazine and 1-(benzo[d]isothiazole-3-yl)-4-(2-(oxo, hydroxy, and fluoro)-2-phenylethyl)-piperazine derivatives were synthesized through nucleophilic substitution reaction of phenacyl bromides with hetero arylpiperazine, reduction, and then fluorination. Compound K2 showed potent activity against gram-negative bacterial stain P. aeruginosa with minimum inhibitory concentration (MIC) value of 12.5 µg/mL. This compound showed better inhibitory activity than the standard drug chloramphenicol.
4/3/2023 10:42:29 PM +00:00
A microwave-assisted highly stereoselective one-pot Wittig reaction under solvent-free conditions
We report a novel microwave-assisted two-step, one-pot protocol for the synthesis of olefins (alkenes) via Wittig reaction. The reaction was carried out under solvent-free conditions using basic alumina both as a heterogeneous catalyst and a solid support. Varieties of aromatic aldehydes were converted into their corresponding olefins within 30–50 min with good to excellent yields. An excellent predominance of E -isomers over Z -isomers (up to 100% E-selectivity) for all the olefin products was observed.
4/3/2023 10:42:22 PM +00:00