Silica supported Ru(salophen)Cl: An efficient and robust heterogeneous catalyst for epoxidation of alkenes with sodium periodate

In the present work, heterogenization of Ru(salophen)Cl via its axial ligation to silica-bound imidazole, SiIm, is reported. The heterogeneous catalyst, [Ru(salophen)Cl–SiIm], was characterized by elemental analysis, SEM, TEM, FT-IR and diffuse reflectance UV–Vis spectroscopic techniques. The catalyst, which is not soluble in water and common organic solvents, was used for efficient epoxidation of cyclic and linear alkenes with NaIO₄ under agitation with magnetic stirring. This new heterogenized catalyst is of high stability and reusability in the oxidation reactions. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene were also investigated.     

Computation of some thermodynamic properties of helium–neon and helium–krypton fluid mixtures using molecular dynamics simulation

We have performed molecular dynamics simulations to obtain internal energy and pressure of helium–neon and helium–krypton mixtures at different densities using accurate recently two-body ab initio potentials supplemented by quantum corrections following the Feynman–Hibbs approach. The significance of this work is that the three-body expression of Wang and Sadus [22] was used to improve prediction of the pressures and internal energies of helium + krypton and helium + neon mixtures without requiring an expensive three-body calculation. Our results show a good agreement with the corresponding experimental data.     

Thermal decomposition route for synthesis of Mn3O4 nanoparticles in presence of a novel precursor

The synthesis of manganese oxide (Mn₃O₄) nanoparticles by using thermal decomposition and its physicochemical characterization are being reported in present investigation. As a new precursor, [bis(2-hydroxy-1-naphthaldehydato)manganese(II)] complex was used in the presence of oleylamine (C₁₈H₃₇N) as both surfactant and solvent to control the size of resulting nanoparticle. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Raman spectrum. Synthesized manganese oxide nanoparticles have a tetragonal structure with average size of 9–24 nm. The phase pure samples were characterized by using X-ray photoelectron spectroscopy (XPS) for Mn 2p level. The values of binding energies are consistent with the relative values are reported in the literature. As a comparison between two methods, the novel precursor thermally was treated in solid state reaction in different temperature, 400, 500, and 600 °C and the products were characterized by SEM images. Magnetic property of the as-prepared Mn₃O₄ nanoparticle shows a ferromagnetic behavior with high saturation magnetization and coercivity.     

On Water: Brφnsted Acidic Ionic Liquid[(CH2)4SO3HMIM][HSO4]Catalysed Synthesis of Oxindoles Derivatives

Some oxindoles derivatives are synthesized from the condensation of indoles with isatins in the presence of green and recycable catalyst [(CH₂)₄SO₃HMIM][HSO₄] in water at room temperature.     

Dyadic Green’s function of a PEMC cylinder

The dyadic Green’s function of a PEMC cylinder is derived with the aid of the principle of scattering superposition and Ohm–Rayleigh method. The PEMC boundary conditions are presented in dyadic form and it shows that how the impedance parameter of PEMC and cross-polarized fields appear in the Green’s function. The asymptotic expansions of the dyadic function is calculated in order to attain a closed form for the electrical field.     

The competition between the intramolecular hydrogen bond and π‐electron delocalization in trifluoroacetylacetone—A theoretical study

Conformational study of trifluoroacetylacetone was carried out using the HF, B3LYP, and MP2 methods with the 6‐31G(d, p) and 6‐311++G(d, p) basis sets. All of the results show that the chelated enol structures (E11 and E31) have extra stability with respect to the other forms and one of them (E11) is global minimum. The energy gap between the chelated forms is in the range 0.7–5.9 kJ mol^?1. Theoretical calculations show that this compound has an asymmetric double minimum potential energy surface which is in contrast with the electron diffraction result. Moreover, the computational results predict that due to the withdrawing effect of CF₃ group, hydrogen bond in trifluoroacetylacetone is weaker than the acetylacetone. Because of the more stability of E11, it is expected that the hydrogen bond energy in E11 is greater than the E31, but at all of the computational levels with most extended basis set the converse results were observed. These results clearly show that the hydrogen bond is not a superior parameter in conformational preference and the contribution of resonance is probably greater than the hydrogen bond. Finally, the analysis of this system by quantum theory of atoms in molecules and natural bond orbital methods fairly support the ab initio results. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

High‐Selective Tramadol Sensor Based on Modified Molecularly Imprinted Polymer?Carbon Paste Electrode with Multiwalled Carbon Nanotubes

We report here a novel carbon paste electrode (CPE) which is able to quantitatively sense tramadol under physiological conditions without sample preparation step. The selectivity of CPE is modified by applying molecularly imprinted polymer (MIP) technology. Multiwalled carbon nanotubes (MWCNTs) are incorporated in the structure of CPE to improve the conductivity and the ion‐to‐electron transduction. The electrode shows a wide dynamic linear range for tramadol from 10^?7 to 10^?3 M. The observed limit of detection and % RSD are 5×10^?7 M and 1.8 %, respectively. Finally, the proposed method is applied to determine tramadol in urine and medicinal tablets.     

Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer (Ce(IV)–G2): A novel and efficient dendritic catalyst for the synthesis of pyrido[3,2-c]coumarin derivatives

In this study, a new and stable Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer was designed, synthesized, and characterized using Fourier-transform infrared, elemental analysis, thermogravimetric analysis, field emission scanning electron microscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering, Brunauer–Emmett–Teller, and inductively coupled plasma optical emission spectroscopy techniques. This catalyst was efficiently used for the one-pot, single-step multicomponent synthesis of pyrido[3,2-c]coumarins from 4-aminocoumarin, aldehydes, and aryl ketones. The efficiency and selectivity of this catalytic system were also evaluated for the synthesis of pyrido[3,2-c]coumarins from terminal/internal alkynes instead of aryl ketones. In this respect, the regioselectivity of the products was successfully assigned by X-ray crystallographic analysis. All these reactions were best performed under solvent-free conditions in the presence of only 0.28 mol% of the catalyst, and such a one-pot multicomponent synthesis of pyrido[3,2-c]coumarins is reported for the first time. It is also worth noting that single-step and short reaction path for the synthesis of a variety of pyrido[3,2-c]coumarins along with excellent reusability of this dendritic catalyst makes this method economically and environmentally attractive.