Structural elucidation of propargylated products of 3-substituted-1,2,4-triazole-5-thiols by NMR techniques

Propargylation of 3-substituted-1,2,4-triazole-5-thiols, which predominantly exist as their thione tautomers, was carried out with the view to synthesize different heterocycles and study their biological activity. Three different products namely, a mono S-propargyl and two S,N-dipropargyl regioisomers, arising from N1/N2 substitution, were isolated and characterized. Unambiguous structural elucidation of the regioisomers of S,N-dipropargyl derivatives was achieved by means of (13)C-(1)H HMBC technique. The proportion of the regioisomers was found to vary with the substituent on the 1,2,4-triazole thiols. No product corresponding to N4 substitution was isolated from any of the reactions carried out.     

Two-component density functional theory of positron binding to negative ions

The problem of binding in positron-negative ion systems has been addressed via two-component density functional theory. Calculations have been performed within the local density approximation for electron exchange-correlation as well as for the electron-positron correlation potential using a self-interaction corrected version of the density functional equations. Our results indicate that a positron forms a stable bound state with the negative ions Li⁻,B⁻,C⁻,O⁻,F⁻ and Cl⁻ with respect to dissociation into a negative ion and a positron or a neutral atom and positronium. Inclusion of electron-positron correlation deepens the positron bound state and stabilizes the system compared to earlier exchange-only calculations.     

Application of thermogravimetric analysis for characterisation of bisdithiocarbamate of urea and its copper (II) complex

A novel disodium salt of bisdithiocarbamate of urea (UBDT) and its Cu(II) complex Cu(II)UBDT were prepared and characterised by elemental analysis, IR, electronic and NMR spectroscopy, conductivity measurements and thermogravimetric analysis (TGA). Water-soluble UBDT possessed good chelating ability for various metal ions. Its copper (II) complex, Cu(II)UBDT was amorphous, intractable solid having polymeric structure. The ligand as well as the complex was found to possess high thermal stability. UBDT cyclised on heating to yield a heterocyclic compound (“X”, probably highly stabilised by resonance) which also showed coordinating tendency for various metal ions.     

Preparation of nanosized gold particles in a biopolymer using UV photoactivation

Gold nanoparticles have been prepared by UV photoactivation in the presence of a biopolymer, sodium alginate. The particles are characterized by UV-vis spectra and TEM studies. Both particle size and the UV-visible absorption peak are dependent on the sodium alginate concentration. The effects of various other parameters such as change of light source, cell material of the reaction chamber, heating effect, irradiation time, and HAuCl4 concentration are studied. The particles are spherical and in situ stabilized by the biopolymer. The method is very simple and reproducible.     

Shape-controlled Synthesis of Gold Nanoparticles from Gold(III)-chelates of β-diketones

Chelating ligands with β-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes out of aqueous HAuCl₄ solutions. Evolution of stable gold nanoparticles happens to be first order with respect to gold particles having rate constants ∼ ∼10⁻² min⁻¹ and subsequent chlorine insertion in the β-diketone skeleton is reported as a general feature. Spherical or triangular or hexagonal particle evolution goes selectively under the influence of different β-diketones in terms of capping and reducing capabilities of the reductants.     

Intriguing Manipulation of Metal‐Enhanced Fluorescence for the Detection of CuII and Cysteine

Commercially available salicylaldehyde, in alkaline medium, exhibits strong fluorescence after one hour of UV exposure in the presence of Ag^I. The phenolic group of salicylaldehyde is converted into the quinone form under alkaline conditions in the presence of AgNO₃, resulting in aggregated Ag(0), which causes approximately 250 times fluorescence enhancement of the in situ produced quinone. Such high silver‐enhanced‐fluorescence (SEF) is selectively quenched by cysteine, arginine, histidine, methionine, and tryptophan. In contrast to the other amino acids, ageing brings selectivity of the cysteine‐induced quenching effect. Interestingly, Cu^II is found to be the only metal ion that exclusively regenerates the lost fluorescence. Thus, quenching and recovery of fluorescence (Turn Off/On) can be used for the selective and sensitive detection of cysteine as well as Cu^II ions in one pot. Alteration of the electric field density around the fluorophore (lightening rod effect) and scattering/absorption cross‐section have been proposed to account for the Off/On fluorescence.     

Metal oxides nanocomposite membrane for biofouling mitigation in wastewater treatment

These days our one of the major challenges is the treatment of polluted wastewater produced by the growing population and industrial activities. The conventional wastewater treatment methods are costly and need to be more advanced. For this reason, membrane technology has been used as an effective wastewater treatment method for many decades due to its high removal power, selectivity, and permeability properties. Biofouling causes a serious concern related to membrane permeability, shortens membrane life, and selectivity. Polymeric membranes are widely used in wastewater treatment due to their good pore-forming ability, higher flexibility, and relatively low costs but are limited to their hydrophobicity property and more susceptible to fouling. Metal oxides nanomaterials are widely used in the formation of polymer nanocomposite membranes because of their hydrophilicity, larger surface area, pore channels, and high toxicity towards pathogenic micro-organisms. In this review, we have discussed the factors affecting membrane biofouling and their conventional and current treatment methods with their limitations. We have also referred to the use of metal oxide nanomaterials, as an antibacterial agent, for the fabrication of polymer nanocomposite membranes and discuss their antibacterial activity with antibiofouling behavior.     

Synthesis and Characterization of a Novel Heterocyclic Schiff Base and Development of a Fluorescent Sensor for Vitamin B12

Journal of Fluorescence - A heterocyclic Schiff base (MPDPI)was synthesized by the condensation reaction of 1-phenylisatin with 4,5-dimethylphenylene diamine. It was characterized by using...     

Resin-immobilized CuO and Cu nanocomposites for alcohol oxidation

Resin immobilized stable, spherical CuO nanoparticles prepared in the presence of cyclodextrin (CD) act as catalysts for liquid phase alcohol oxidation in air. The catalytic activity of the CuO nanocomposites and its green chemistry approach make it superior to the related resin-bound Cu(0) nanocomposite. The effect of alcohol chain length and electron-donating or -withdrawing groups influence product yield. The nanocomposites exhibit good reusability, simple workup procedure, and a straightforward approach to aldehyde formation.     

Evaluation of mosquito larvicidal activity of fruit extracts of Acacia auriculiformis against the Japanese encephalitis vector Culex vishnui

The larvicidal potentiality of crude and ethyl acetate extracts of fruits of Acacia auriculiformis was investigated against all the larval instars of JE vector Culex vishnui. The crude extracts showed good results against all the larval instars with highest mortality at 0.09%. Highest mortality was found at 300 ppm of ethyl acetate extract. Lowest LC₅₀ value was obtained at 72 h for third instar larvae. Non target organisms tested, showed no to very less mortality to ethyl acetate solvent extract. Presence of N–H stretching, a C=O stretching, C=C and C–N stretching vibrations of secondary amide or amine group were confirmed from IR analysis. GC-MS analysis revealed the presence of three compounds namely Ethane 2-chloro-1,1-dimethoxy, Acetic acid, 1-methyl ether ester and [4-[1-[3,5-Dimethyl-4[(trimethylsilyl)oxy)phenyl]-1,3-dimethylbutyl)-2,6dimethylphenoxy)(trimethyl) silane, responsible for mosquito larval death.