The molecular diversity scope of 4-hydroxycoumarin in the synthesis of heterocyclic compounds via multicomponent reactions

Molecular Diversity - 4-Hydroxycoumarins are some of the most versatile heterocyclic scaffolds and are frequently applied in the synthesis of various organic compounds. 4-Hydroxycoumarin-based...     

Understanding the domino reactions of alkyne-tethered N-tosylhydrazones yielding fused polycyclic pyrazoles. An MEDT study

The domino reactions of alkyne-tethered N-mesylhydrazones yielding fused polycyclic pyrazoles have been studied within the Molecular Electron Density Theory (MEDT). Analysis of the Gibbs free energies indicates that the more favourable reactive path is the one in which the elimination of mesylate anion takes place before the intramolecular [3 + 2] cycloaddition (IM32CA) reaction, which corresponds with the rate-determining step of these domino processes. ELF topological analysis of the bond formation along the IM32CA reaction indicates that in spite of the high activation energy associated to this intramolecular reaction, it shows a pmr-type mechanism characterised by the presence of a pseudoradical carbon at the phenyldiazomethane framework.     

Calculation of the Coulomb potential between spherical-deformed and deformed-deformed nuclei using the Monte Carlo method

The Coulomb potential between spherical-deformed and deformed-deformed nuclei has been calculated using the Monte Carlo simulation. The results obtained for the Coulomb potential in the ¹⁶O$ + $²³⁸U and ²⁷Al$ + $⁷⁰Ge reactions are in good agreement with those obtained using the double-folding method. The simulation technique employed here has the ability of calculating the Coulomb potential taking into account the finite diffuseness parameter, all the possible deformation degrees of freedom, and different orientations of the symmetry axes of the target and the projectile nuclei with respect to each other. The accuracy of this simulation technique is high and the computer time taken to do these calculations is much less than those of the double-folding method.     

Photo and Chemical Reduction of Copper onto Anatase‐Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts

In this study, the photocatalytic efficiency of anatase‐type TiO₂ nanoparticles synthesized using the sol–gel low‐temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV–light‐assisted photo and NaBH₄‐assisted chemical reduction methods were used for deposition of copper onto TiO₂. The surface hydroxyl groups of TiO₂ were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed‐bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH‐modified Cu/TiO₂ nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO₂ due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO₂ toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH₄ concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH‐modified Cu/TiO₂ nanoparticles.     

Surface tailoring control in micelle templated silica

Surface tailoring control was studied using new concept surface-protector (SP) group that can covered a part of surface. In micelle templated silica, cationic surfactant had the role of SP group. Various methods of silylation on the surface coverage was done on the hexagonal micelle templated silicas and the samples was characterized using BET surface measurement, pore size distribution, FT-IR and ¹³C and ²⁹Si MAS NMR. Direct silylation of micelle templated silica still containing the templating surfactant can lead to total or partial silylation of the internal (and external) surface depending on the silylation agent. A mixture of chlorotrimethylsilane in hexamethyldisiloxane leads to full coverage by trimethylsilyl groups and to a very hydrophobic surface. Using hexamethyldisilazane, the silylation drops down to 45-65% and displaces only partially the templating CTMA⁺ surfactant. The displacement of the remaining surfactant molecules leaves behind hydrophilic nests of the size of the ammonium heads (∼0.7 nm²). Cation exchange can be performed on these nests at pH to 10 without structure collapse.     

Novel method for the fast preconcentration and monitoring of a ppt level of lead and copper with a modified hexagonal mesoporous silica compound and inductively coupled plasma atomic emission spectrometry.

A novel method for the rapid extraction and determination of a ppt level of Pb2+ and Cu2+ ions using partial silylated MCM-41 modified by a new salophen and inductively coupled plasma atomic emission spectrometry (ICP-AES) is introduced. The preconcentration factor of the method is 500, and the detection limits of Pb2+ and Cu2+ are 335 and 34 ng L(-1), respectively. The time and efficiency of extraction, the pH and flow rate, the type and minimum amount of acid for stripping of Pb2+ and Cu2+ from modified MCM-41 and the break-through volume were investigated. The maximum capacity of 4 mg of silylated MCM-41 modified by salophen used was found to be 150 +/- 4 and 117 +/- 3 microg of Pb2+ and Cu2+, respectively.     

Preparation of CaWO4:Ln@SiO2 (Ln=Tb, Dy and Ho) nanoparticles by a combustion reaction and their optical properties

The CaWO₄:Ln³⁺@SiO₂ (Ln=Tb, Dy and Ho) nanoparticles were synthesized via a combustion process at 800 °C, using citric acid as chelating agent and fuel, ammonium nitrate as fuel, boric acid as flux material and silica as supports. The persistent phosphor nanoparticles were characterized by X-ray diffraction (XRD), reflectance UV-vis and fluorescence spectroscopy (PL) and transmission electron microscopy (TEM) techniques. XRD patterns indicated that crystalline calcium tungstate with scheelite structure was produced. The reflectance UV-vis spectra showed the broad absorption band of groups and the PL spectra showed the wide excitation band, broad emission band of and characteristic emissions of Ln³⁺ ions. The average particle sizes were determined by TEM, which are about 50 nm.     

Ricci cubic gravity in d dimensions,gravitons and SAdS/Lifshitz black holes

A special class of higher curvature theories of gravity, Ricci cubic gravity (RCG), in general d dimensional space-time has been investigated in this paper. We have used two different approaches, the linearized equations of motion and the auxiliary field formalism to study the massive and massless graviton propagating modes of the AdS background. Using the auxiliary field formalism, we have found the renormalized boundary stress tensor to compute the mass of the Schwarzschild–AdS and Lifshitz black holes in RCG theory.     

Efficient One‐Pot Solvent‐Free Synthesis of 1H‐Pyrazolo[1,2‐b]phthalazine‐5,10‐diones Catalyzed by Sulfonic Acid Functionalized Nanoporous Silica (SBA‐Pr‐SO3H)

A green protocol has been developed for the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐diones by one‐pot cyclocondensation reaction of phthalhydrazide, aromatic aldehydes, and malononitrile or ethyl cyanoacetate using sulfonic acid functionalized SBA‐15 (SBA‐Pr‐SO₃H) as a heterogeneous solid acid catalyst under solvent‐free conditions.