Heterogeneous NaHSO4·SiO2 catalyzed ‘one-pot’ synthesis and in vitro antibacterial and antifungal activities of pyridino-1,2,3-thiadiazoles

A ‘one-pot’ synthesis of 5,7-diaryl-4,4-dimethyl-4,5,6,7-tetrahydropyridino[4,3-d]-1,2,3-thiadiazoles (11–15) using NaHSO₄·SiO₂ heterogeneous catalyst in dry media under microwave irradiation by a simple synthetic strategy is described. Among the synthesized 1,2,3-thiadiazoles, compounds having electron withdrawing chloro- and fluoro- functional group on the aryl moiety 14 and 15 exerted a wide range of modest antibacterial and antifungal activity in vitro against the tested organisms. The obtained results may be used as a key step for the building of novel chemical compounds with interesting antimicrobial profiles comparable with that of the standard drugs.     

Seed Oil Based Zinc Bioactive Polymers: Synthesis, Characterization and Biological Studies

Zinc containing oil based polyesteramide resins were synthesized by condensation polymerization reaction between castor/soyabean oil derived castor/soyabean fatty amide diol (HECA/HESA), Zn (OH)₂ and adipic acid. The conventional spectroscopic techniques such as FTIR, ¹HNMR, ¹³CNMR have been used to establish the structure of the polymers. Standard laboratory methods were used to study the physicochemical characteristics like acid value, hydroxyl value, saponification value, iodine value, specific gravity, and viscosity. The thermal behaviour of the polymers was analyzed by using thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). In vitro antifungal (anticandidial) activity of the polymers was studied against C. albicans ATCC-10261, C. glabrata ATCC-90030 and C. tropicalis ATCC-750, respectively. Antibacterial activity against Gram positive (S. subtillis) and Gram negative bacteria (E. coli and S. typhi) was also examined. For more accuracy, growth curve studies were carried out with the polymer SZ showing higher biological activity against E. coli by using conventional spectrophotometer. The result showed that the polymers have potent anticandidial and antibacterial activities.     

Design, ‘one-pot’ synthesis,characterization, antibacterial and antifungal activities of novel 6-aryl-1,2,4,5-tetrazinan-3-thiones in dry media

A novel ‘one-pot’ synthesis of 6-aryl-1,2,4,5-tetrazinan-3-thiones is carried out by the three-component coupling of thiourea, various structurally diverse aromatic aldehydes and ammonium acetate in the presence of reusable NaHSO₄·SiO₂ heterogeneous catalyst in dry media under microwave irradiation. FT-IR, ¹H NMR, D₂O Exchange, HOMOCOR, ¹³C NMR, MS and elemental analysis characterize all the synthesized compounds. In vitro antibacterial/fungal activities are carried out for all the synthesized eight new compounds. All the compounds are more active against bacterial strains namely Staphylococcus aureus, β-Heamolytic streptococcus, Vibreo cholerae, Salmonella typhii, Shigella felxneri, Klebsiella pneumonia and Pseudomonas except compounds 1 and 6, while compound 6 shows promising activity against Salmonella typhii. Moreover, of all the compounds tested, compounds 3 and 8 are more effectual against all the tested fungal strains.     

Thiazole derivatives‐functionalized polyvinyl chloride nanocomposites with photostability and antimicrobial properties

Polyvinyl chloride (PVC) was modified via substitution reaction with 2‐aminothiazole and ethyl 2‐aminothiazole‐4‐carboxylate separately in the absence and in presence of silver (AgNPs) or copper (CuNPs) nanoparticles, using metal salts as precursors, in 3% (w/w) with respect to PVC. The functionalized PVC‐nanocomposites have been characterized via FTIR, ¹HNMR spectroscopic analyses, in addition to the morphological investigation such as scanning (SEM) and transmission electron microscopy (TEM). Spectral data confirmed the introduction of the thiazole (ester) to the PVC backbone. TEM analysis showed that the sizes of the AgNPs and CuNPs have fallen in the range of 10–30 nm and 30–50 nm for the prepared nanocomposites, respectively. Evaluating the photostability of modified nanocomposites was estimated by following the extent of discoloration for UV‐irradiated samples colorimetrically in accordance with the irradiation time. The antimicrobial activity of the modified nanocomposites was explored against three Gram+ve bacteria (Bacillus subtilis, Staphylococcus aureus, and Streptococcus faecalis), three Gram‐ve bacteria (Escherichia coli, Neisseria gonorrhoeae, and Pseudomonas aeruginosa), and two fungi (Candida albicans and Aspergillus flavus). Aminothiazole (ester)‐functionalized PVC exhibited significant antimicrobial efficiencies against the investigated pathogens. However, incorporation of AgNPs or CuNPs to the modified PVC enhanced their inhibitory effect against the microorganisms under investigation. J. VINYL ADDIT. TECHNOL., 25:E137–E146, 2019. © 2018 Society of Plastics Engineers     

Synthesis, Characterization and Biological Studies of Oil Based Tin Polymer

The antimicrobial activity of a newly prepared vegetable oil based organotin polymer by the condensation reaction between fattyamide diol (N, N¹-bis 2 hydroxy ethyl castor oil fatty amide) and butyltin chloride dihydroxide has been studied against the bacterial species E. coli, S. typhi (Gram-negative), S. subtillis, S. aureus (Gram-positive) and three fungal strains (Candida albicans ATCC-10261, Candida glabrata ATCC-90030, Candida tropicalis ATCC-750). The antifouling property of this polymer has also been investigated. The conventional spectroscopic techniques such as FTIR, ¹H-NMR and ¹³C-NMR have been used to establish the structure of the polymer. The physicochemical characteristics like acid value, hydroxyl value, saponification value, iodine value, specific gravity and viscosity were determined by standard laboratory methods. In addition the thermal stability was analysed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The polymer was found fairly active against the tested microbial species and showed antifouling property.     

Synthesis and antimicrobial activities of some ethyl 2-arylthio-6-arylimidazo[2,1-b]thiazole-3-carboxylates and their sulfones

A series of new 2-arylthio-3-ethoxycarbonyl-6-arylimidazo[2,1-b]thiazoles (4a–4h) and 2-arenesulfonyl-3-ethoxycarbonyl-6-arylimidazo[2,1-b]thiazoles (5a–5h) have been prepared and characterized by analytical and spectral methods. The title compounds 4a–4h and 5a–5h were obtained by the reaction of 2-amino-4-ethoxycarbonyl-5-arylthiothiazoles (2a and 2b)/2-amino-4-ethoxycarbonyl-5-arenesulphonyl-thiazoles (3a and 3b) with various phenacyl bromides in anhydrous ethanol. These newly synthesized compounds (4a–4h and 5a–5h) were screened for their antibacterial activity against Gram-negative bacterium Escherichia coli, Gram-positive bacterium Staphylococcus aureus, and antifungal properties against Aspergillus niger and Candida albicans.     

Estimation of the effectiveness factor of an outer-sphere redox couple (Fe3+/Fe2+) using rotating disk Ti/IrO2 electrodes of different loading

The effectiveness factor; E _f , defined as the fraction of the surface that participates effectively in a given reaction, is an important parameter when operating three-dimensional (3D) electrodes. The rotating disk electrode (RDE) technique with the Fe³⁺/Fe²⁺ redox couple as a probe reaction has been used for the evaluation of the effectiveness factor of 3D Ti/IrO₂ electrodes with different IrO₂ loading. For this purpose, steady-state polarization measurements using Ti/IrO₂ rotating disk electrodes in 0.5 M Fe³⁺/Fe²⁺ in 1 M HCl were carried out under well-defined hydrodynamic conditions. The low-field approximation relation has been used for the estimation of the exchange current densities j ₀, of the Fe³⁺/Fe²⁺ redox couple. It was found for this redox couple that the effectiveness factor is very low (<2%) and essentially the 2D electrode surface area works effectively in the steady-state polarization measurements.     

Efficiency and Mechanism of Ciprofloxacin Hydrochloride Degradation in Wastewater by Fe3o4/Na2S2O8

ABSTRACT

The nanosized Fe₃O₄ catalyst was synthesized via a modified reverse coprecipitation method and characterized by means of a scanning electron microscope (SEM) and an X-ray diffraction (XRD) analysis instrument. The degradation efficiency and reaction rate of Fe₃O₄ in activating sodium persulfate used to degrade ciprofloxacin were determined from the catalyst dosage, oxidant concentration, and initial pH. The results showed that under the optimum conditions of a catalyst dosage of 2.0 g·L^?1, a sodium persulfate concentration of 1.0 g·L^?1, and an initial pH of 7, the degradation rate of ciprofloxacin was 93.73%, the removal rate of total organic carbon was 78%, and the first-order reaction constant was 0.06907 min^?1 within 40 min. It was also demonstrated that the reactive oxygen species in the Fe₃O₄/sodium persulfate catalytic system were mainly composed of SO₄^– and supplemented by OH· and HO₂· using probe compounds such as ethanol, tertiary butanol, and benzoquinone.     

Synthesis and characterization of polypyrrole/TiO2 composites on mild steel

The anodic codeposition of polypyrrole and TiO₂ on AISI 1010 steel substrates in oxalic acid medium was studied from the standpoint of their use as protective coatings against corrosion. The influence of surface treatment, pH, stirring and current density (j) on the current efficiency () and pigment concentration incorporated in the polymer (C _c) were investigated. The highest C _c values (7.5%) were found at j = 5 mA cm^–2, pH 4 and stirred baths. The composites were characterized by adherence and surface roughness tests, XPS, EDX, SEM, FTIR and cyclic voltammetry.     

Photocatalytic decolorization of Basic Blue 41 using TiO2-Fe3O4-bentonite coating applied to ceramic in continuous system

Abstract

Photocatalytic degradation/decolorization of Basic Blue 41 dye assisted by UV radiation has been studied over TiO₂-Fe₃O₄ supported by bentonite. In this experiment, photocatalytic decolorization process was performed continuously; where dye feed solution was supplied to a coated-ceramic vessel. The influence of the initial concentration, pH, and flow rate of the dye feed solution on the degradation efficiency process was examined in this study. The results showed that the increase in the dye concentration and flow rate reduces decolorization efficiency. The highest decolorization efficiency was at pH of 5.5. The kinetic study of this photo-decolorization indicated that under the experimental condition, the photocatalytic kinetic process followed first-order kinetics on the basis of Langmuir–Hinshelwood heterogeneous reaction mechanism, where the reaction rate constant, namely k_r, is 0.7707 and the adsorption rate constant, namely K, is 0.01298.     

Synthesis and antimicrobial evaluation of some pyrazolo-thiazolyl alkoxy-1H-isoindole-1, 3(2H)-dione derivatives

1,3-Thiazolidine-2,4-dione 2 has been synthesized by the cyclisation reaction of thiourea and chloroacetic acid in the presence of ethanol. The reaction of compound 2 with substituted aromatic aldehyde afforded the corresponding derivatives of substituted 5-benzylidene-1,3-thiazolidinone-2,4-dione 3a–d, which upon reflux with ω-bromoalkoxyphthalimide gave 2-{[-5-(substituted benzylidine)-2,4-dioxo-1,3-thiazolidine-3-yl]alkoxy} -1H-isoindole-1,3(2H)-dione 4a–i. Further, compounds 4a–i were treated with phenyl hydrazine and 2,4 dinitro phenyl hydrazine in the DMF to yield the title compound 2-[5-oxo-2,3-substituted diphenyl-2H-pyrazolo[3,4-d][1,3]thiazol-6(5H)-yl)alkoxy]-1H-isoindole-1,3(2H)-dione 5a–r. Structures of newly synthesized compounds were established based on elemental analysis, IR, ¹H NMR and mass spectral data. Synthesized compounds have been assayed for their antibacterial activities against B. subtilis, K. pneumoniae, P. aeruginosa and S. aureus and antifungal activities against A. fumigatus and C. albicans.     

A Highly Flexible Green Synthesis of 3,4,5-Substituted Furan-2(5H)-ones Using Nano-CdZr4(PO4)6 as Catalyst under Microwave Irradiation

A concise and efficient method for the synthesis of 3,4,5-substituted furan-2 (5H)-ones was achieved through a three-component reaction of amines, dialkyl acetylene dicarboxylate, and aromatic aldehydes using nano-CdZr₄(PO₄)₆ as catalyst under microwave irradiation. This method has several advantages such as, high efficiency, short reaction times, simple workup, and recyclability of the catalyst up to seven runs without considerable loss of activity.     

Effect of ZnO on Mg2TiO4–MgTiO3–CaTiO3 microwave dielectric ceramics prepared by reaction sintering route

ZnO-doped Mg₂TiO₄–MgTiO₃–CaTiO₃ microwave dielectric ceramics were successfully prepared by the reaction sintering route. The compact samples consisted of MgTiO₃, Mg₂TiO₄ and CaTiO₃, which was confirmed by X-ray diffraction and energy-dispersive spectra. ZnO efficiently lowered the sintering temperature and promoted the densification, as well as the improvements in the dielectric constant and the quality factor. At the level of ZnO?=?1 wt-%, the ceramics exhibited optimum microwave dielectric properties: a dielectric constant of 20.3, a high quality factor of 64,740 GHz (at 9.9 GHz) and a near-zero temperature coefficient of resonant frequency (–1.3 ppm/^oC) after sintering at 1320^oC for 4 h.     

Hydrothermal solvothermal synthesis and microwave absorbing study of MCo2O4 (M = Mn,Ni) microparticles

ABSTRACT

MCo₂O₄ (M?=?Mn,Ni) microparticles were synthesised by a simple hydrothermal solvothermal method. The samples were characterised by X-ray diffraction, X-ray energy dispersive spectroscopy and scanning electron microscopy, which showed that MnCo₂O₄ microparticles with spherical particles aggregated by a large number of small cubes and cubic shaped NiCo₂O₄ microcubes were obtained. The microwave absorption properties of these products were systematically investigated by vector network analysis. Results indicated that the minimum reflection loss value of MnCo₂O₄ microparticles was ?26.34?dB at 11.04?GHz with the absorber thickness of 2.5?mm, which was much lower than that of NiCo₂O₄ microcubes with the same absorber thickness. The possible mechanism was analysed, indicating that the geometry and size of MCo₂O₄ (M?=?Mn,Ni) microparticles played a key role in microwave absorption.     

Synthesis and evaluation of biological activities of 4-cyclopropyl-5-(2-fluorophenyl) arylhydrazono-2,3-dihydrothiazoles as potent antioxidant agents

A new series of 4-cyclopropyl-5-(2-fluorophenyl)arylhydrazono-2,3-dihydrothiazole derivatives was synthesized via the reaction of prepared thiosemicarbazones with 2-bromo-1-cyclopropyl-2-(2-?uorophenyl)ethanone in the presence of Et₃N as a catalyst through a semi Hantzsch cyclization. The optimized reaction conditions for this one-pot reaction were achieved. The products were obtained in short reaction times, high yields and high purities. Antioxidant activity of products was evaluated using DPPH (2,2-diphenyl-2-picrylhydrazyl) and ABTS 2,2-azinobis(3-ethylbenzothiazoline-sulfonate) assays. Products showed higher antioxidant activity using the ABTS method. Compounds 5c and 5g showed lower IC₅₀ values compared with ascorbic acid as a standard. Compounds 5a–5h possessed moderate to high antioxidant activity by both methods. Also, antibacterial activity of 5a–5h was evaluated against gram-positive and gram-negative bacterial strains. None of the compounds inhibited A. hydrophila, while they had moderate to low inhibitory activity against other tested bacterial strains.     

A Facile and Efficient Synthesis of Diaryl Amines or Ethers under Microwave Irradiation at Presence of KF/Al2O3 without Solvent and Their Anti-Fungal Biological Activities against Six Phytopathogens

A series of diaryl amines, ethers and thioethers were synthesized under microwave irradiation efficiently at presence of KF/Al₂O₃ in 83%–96% yields without any solvent. The salient characters of this method lie in short reaction time, high yields, general applicability to substrates and simple workup procedure. At the same time, their antifungal biological activities against six phytopathogen were evaluated. Most of the compounds (3b, 3c, 3g–o) are more potent than thiophannate-methyl against to Magnaporthe oryzae. This implies that diaryl amine or ether moiety may be helpful in finding a fungicide against Magnaporthe oryzae.     

Effect of WSi2 addition on densification and properties of ZrB2

Abstract

Effect of WSi₂ addition on densification and properties of ZrB₂ has been investigated. Samples of the following composition with controlled addition of WSi₂ were prepared by hot pressing (1) ZrB₂, (2) ZrB₂+2·5%WSi₂, (3) ZrB₂+5%WSi₂ and (4) ZrB₂+10%WSi₂. Hot pressing of monolithic ZrB₂ at 1750°C resulted in achieving a density of only 80·1% ρ_th. Addition of WSi₂ enhanced the densification and resulted in near theoretical density. Microstructural investigations revealed the presence of reaction product containing Si and Zr. An increase in WSi₂ content led to an increase in hardness of the product. A slight increase in fracture toughness was observed with WSi₂ addition. Crack deflection was observed in the microstructure. Oxidation study of the composite samples revealed that the oxidised layer is not adherent and resulted in spallation at the end of the test.     

Influence of magnesia doping on structure and electrical conductivity of pyrochlore type GdSmZr2O7

Abstract

Polycrystalline ceramic samples of magnesia doped GdSm_1–xMg_xZr₂O_7–x/2 have been prepared by conventional solid state reaction method using high purity oxides. The influence of magnesia dopant content on densification, microstructure and electrical properties of GdSm_1–xMg_xZr₂O_7–x/2 ceramics are investigated. Magnesia doping promotes the sintering densification behaviour of GdSm_1–xMg_xZr₂O_7–x/2 ceramics. GdSm_1–xMg_xZr₂O_7–x/2 (x?=?0, 0·05, 0·10) ceramics have a single phase of the pyrochlore type structure, while GdSm_1–xMg_xZr₂O_7–x/2 (x?=?0·15, 0·20) ceramics consist of the pyrochlore type structure and a small amount of magnesia as the second phase. The total conductivity of GdSm_1–xMg_xZr₂O_7–x/2 ceramics obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm_1–xMg_xZr₂O_7–x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1·0×10^–4 to 1·0 atm at each test temperature. The maximum value of the total conductivity is 1·29×10^–2 S cm^–1 at 1173 K for the GdSm_0·85Mg_0·15Zr₂O_6·925 ceramic.     

Spectroscopic and Thermal Studies of Mn(II), Fe(III), Cr(III) and Zn(II) Complexes Derived from the Ligand Resulted by the Reaction Between 4-Acetyl Pyridine and Thiosemicarbazide

Transition metal complexes of Mn(II), Fe(III), Cr(III) and Zn(II) metal ions with a general formulas [Mn(L)₂(Cl)₂]·4H₂O (I), [Fe(L)₂(Cl)₂]·Cl·6H₂O (II), [Cr(L)₂(Cl)₂]·Cl·6H₂O (III) and [Zn(L)₂(Cl)₂]·2H₂O (IV) where L = 4-acetylpyridine thiosemicarbazone, have been synthesized and interpreted using CHN elemental analysis, magnetic susceptibility measurements, molar conductance, thermal analysis and spectroscopic techniques; i.e., infrared, electronic UV/vis, ¹H-NMR and mass. The manganese(II), ferric(III), chromium(III) and zinc(II) complexes have octahedral geometry. The molar conductance measurements reveal that the Mn(II) and Zn(II) chelates are non-electrolytes but Fe(III) and Cr(III) have an electrolytic behavior. The IR spectra show that the 4-acetylpyridine thiosemicarbazone free ligand is coordinated to the metal(II) chlorides as a neutral bidentate ligand through both of the lone pair of electrons of the C=N azomethine group and C=S group. X-ray powder diffraction gives an impression that the resulting complexes are amorphous and different from the start materials. The thermogravimetric studies indicate that uncoordinated water molecules are lost in the first and second decomposition steps. The activation thermodynamic parameters E*, ΔH*, ΔS* and ΔG* are estimated from the differential thermogravimetric analysis (DTG) curves using Horowitz–Metzger (HM) and Coats–Redfern (CR) methods. The ligand and its complexes have been screened for antibacterial and antifungal activities against two bacteria; i.e., Escherichia coli (Gram −ve) and Bacillus subtilis (Gram +ve) and two fungi, i.e., tricoderma and penicillium activities).