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.     

Influence of Ground State Spin of Projectile-Target on Fission Anisotropies

Fission fragment anisotropies have been investigated for various systems produced in heavy-ion reactions at near and sub-barrier energies. In particular, special attention has been paid to the entrance channel dependence of fragment angular anisotropies. The results of our analysis of the fragment angular anisotropies induced by boron, carbon, and oxygen ions on Thorium and Neptunium targets as well as Fluorine ions on Neptunium target indicate strong dependence of fragment anisotropies on the channel spin, in consistence with the predication of the pre-equilibrium model.     

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.     

SBA-Pr-IS-MN synthesis and its application as Ag+ optical sensor in aqueous media

Research on Chemical Intermediates - A new functionalized mesoporous silica entitled SBA-Pr-IS-MN was produced and characterized by diverse techniques like FT-IR, TGA, XRD, SEM, TEM, and BET....     

The systematic study of the influence of neutron excess on the fusion cross-sections using different proximity-type potentials

Using different types of proximity potentials, we have examined the trend of variations of barrier characteristics (barrier height and its position) as well as fusion cross-sections for 50 isotopic systems including various collisions of C, O, Mg, Si, S, Ca, Ar, Ti and Ni nuclei with the 1 ￡ \leq N/Z < 1.6 condition for compound systems. The results of our studies reveal that the relationships between the increase of barrier positions and the decrease of barrier heights are both linear with the increase of the N/Z ratio. Moreover, fusion cross-sections also enhance linearly with the increase of this ratio.