Molybdenum (VI)‐functionalized UiO‐66 provides an efficient heterogeneous nanocatalyst in oxidation reactions

A novel heterogeneous nanocatalyst was established by supporting molybdenum (VI) on Zr₆ nodes in the structure of the well‐known UiO‐66 metal–organic framework (MOF). The structure of the UiO‐66 before and after Mo (VI) immobilization was confirmed with XRD, DR‐FTIR and UV–vis spectroscopy, and the presence and amount of Mo (VI) was identified by X‐ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy. TEM imaging confirmed the absence of Mo clusters on the MOF surface, while SEM confirmed that the appearance of the MOF has not changed upon immobilizing the Mo (VI) catalyst. BET adsorption measurements were used to confirm the porosity of the catalyst. The catalytic activity of this heterogeneous catalyst was investigated in oxidation of sulfides with H₂O₂ in acetonitrile and oxidative desulfurization of dibenzothiophene. Easy work up, convenient and steady reuse and high activity and selectivity are prominent properties of this new hybrid material.     

Third order harmonics generation in multilayer nanoshells

Third order harmonics generation has been investigated for multilayer nanoshell structure. Numerical calculations show that the nonlinear susceptibility of this structure depends on the parameters such as size and kind of structure, relaxation time and pump photon energy. The intensity and position of third order nonlinear susceptibility peaks depend on shell thicknesses; smaller thicknesses have peak susceptibility at shorter wavelength.     

Acidified,Wet, Silica-Supported Tetrabutylammonium Periodate: A Convenient and Mild Reagent for Conversion of Thioamides to Their Corresponding Amides Under Solvent-Free Conditions

A series of thioamides are transformed to their corresponding oxo analogues in good to excellent yields with acidified, wet, silica-supported tetrabutylammonium periodate under solvent-free conditions.     

A characterization of Finsler metrics of constant flag curvature

Using the notion of C-projectively flatness, we give a new characterization of Finsler metrics of constant flag curvature.     

An efficient,expeditious, and diastereoselective one-pot pseudo-five-component reaction for the synthesis of new bis-Betti bases under catalyst-free conditions

A novel, diastereoselective, one-pot synthesis of new bis-Betti bases via condensation of dihydroxynaphthalene, two equivalents of aryl aldehydes, and two equivalents of 3-amino-5-methylisoxazole is reported. Conversion into the adducts was almost quantitative without the use of solvent or catalyst. The reaction conditions are very simple and enable easy isolation of the product.     

Determination of Trichloroacetic Acid (TCAA) Using CdO Nanoparticles Modified Carbon Paste Electrode

In this paper, the electrochemical behavior of a carbon paste electrode modified with CdO nanoparticles as a potential electrocatalyst for the reduction of trichloroacetic acid (TCAA) was investigated using cyclic voltammetry and double‐potential step chronoamperometry. The modified electrode showed a great enhancement in cathodic peak current with respect to reduction of TCAA in acidic aqueous solution. Using this increment, a quantitative method was developed for the determination of TCAA in aqueous solution. The detection limit and linear dynamic range of TCAA are 2.3×10^?6 M and 2.3×10^?4–3×10^?6 M, respectively.     

Theoretical studies on tautomerism of imidazole-2-selenone

The tautomerism of all possible forms of imidazole selenone (ISe1–ISe6), induced by proton transfer was studied theoretically in different environments including gas phase, continuum solvent, and microhydrated environment with one explicit water molecule. The calculations were performed at the MP2 and CAM-B3LYP levels of theory, separately. It was found that the imidazole selenone, in the form of ISe3, is the most stable isomer in both gas phase and solvent. The activation energy for conversion of ISe3 to imidazole selenol (ISe6), as the second stable form, is 41.72 and 43.0 kcal/mol in the gas phase and water, respectively. The infrared spectral frequencies as well as the vibrational frequency shifts were reported and assigned to their corresponding vibrational modes. In addition, the variation of dipole moments and charges on the atoms with change of solvent was studied. The energies of HOMO, LUMO, and HOMO–LUMO gap were calculated in both gas phase and solvent. Specific solvent effects with addition of water molecule near the electrophilic centers of tautomers and the transition states of proton transfer, assisted by water molecule, were investigated. It was found that the water molecule can form different hydrogen bonds with the molecule. Aggregation of the isomers with water molecule does not change the order of stability of isomers, but proton transfer reaction assisted by a water molecule needs less energy than when the proton shifts through the intramolecular process.     

Homogeneous Liquid–Liquid Microextraction Via Flotation Assistance (HLLME-FA) Method for the Pretreatment of Organochlorine Pesticides in Aqueous Samples and Determination by GC–MS

This work proposes a new, rapid and simple homogeneous liquid–liquid microextraction via flotation assistance technique for the analysis of six organochlorine pesticides in water samples. A special extraction cell was used to facilitate collection of the low-density solvent extract. No centrifugation was required in this procedure. Determination was carried using gas chromatography–mass spectrometry. The water sample solution was then added into the extraction cell containing appropriate mixture of extract and homogeneous solvents. In the first step, a homogeneous solution and then with the continuation of water sample injection, a cloudy solution was formed. Using air flotation, the organic solution was collected at the conical part of the designed cell. The optimized levels of effective parameters were found based on response surface methodology approach. Applying the optimized conditions to the system understudy, the limits of detection of all target analytes were obtained in the range of 1.4–7 ng mL^?1, while the precisions were found to be in the range of 11.08–14.87 (RSD, n = 3). The linearity of the method lay in the range of 10–150 ng mL^?1 with the coefficients of correlation (r ² ) ranging from 0.998 to 0.999.     

Silica Gel Supported Ferric Perchlorate: A New and Efficient Reagent for One Pot Synthesis of Amides from Benzylic Alcohols

Benzylic alcohols react efficiently with nitriles in the presence of silica gel supported ferric perchlorate to produce amides in high yields.