A simple route to 9-fluorenylidenes by domino Suzuki/Heck coupling reactions

A palladium catalyzed domino intermolecular Suzuki followed by intramolecular Heck coupling is described. This strategy afforded a novel and convenient synthesis of various 9-fluorenylidene derivatives in one-pot under relatively mild reaction condition.     

Norharmane: old yet highly selective dual channel ratiometric fluoride and hydrogen sulfate ion sensor

Norharmane provides a simple unexplored class of anion receptor, that allows for the ratiometric selective detection of F(-) and HSO(4)(-) ions. The presence of a strong base can easily form hydrogen bonds with the acidic hydrogen bond donor moiety and the relatively strong acid can easily protonate the basic hydrogen bond acceptor moiety, which can modulate the optical response and can detect the anions efficiently with high selectivity. In view of that, it is promising to conceive the use of these systems in various sensing applications as well as in other situations, such as anion transport and purification, where the availability of cheap and easy-to-make anion receptors, would be advantageous.     

A facile method for the synthesis of copper modified amine-functionalized mesoporous zirconia and its catalytic evaluation in C-S coupling reaction

A new copper modified amine functionalized zirconia has been synthesized by a co-condensation method using zirconium butoxide and aminopropyltriethoxy-silane (APTES) in the presence of a cationic surfactant CTAB followed by impregnation of copper. Nitrogen adsorption-desorption, X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), (13)C nuclear magnetic resonance (NMR), scanning electron micrography (SEM), transmittance electron micrography (TEM), thermo gravimetric analysis-differential thermal analysis (TGA-DTA), X-ray photoelectron spectroscopy (XPS) and UV-vis DRS spectroscopic tools are used to characterize the materials. FT-IR and DRS results indicated the incorporation of Cu and amino groups on the surface of zirconia. This Cu-anchored mesoporous material acts as an efficient, reusable catalyst in the aryl-sulfur coupling reaction between aryl iodide and thiophenol for the synthesis of value added diarylsulfides.     

Electronic and vibrational spectra of some rare earth trifluoromethanesulfonates crystals

Nanocrystalline ZnO powders have been synthesized by a low temperature solution combustion method. The photoluminescence (PL) spectrum of as-formed and heat treated ZnO shows strong violet (402, 421, 437, 485 nm) and weak green (520 nm) emission peaks respectively. The PL intensities of defect related emission bands decrease with calcinations temperature indicating the decrease of Zn(i) and V(o)(+) caused by the chemisorptions of oxygen. The results are correlated with the electron paramagnetic resonance (EPR) studies. Thermoluminescence (TL) glow curves of gamma irradiated ZnO nanoparticles exhibit a single broad glow peak at ～343°C. This can be attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centers. The trapping parameters of ZnO irradiated with various γ-doses are calculated using peak shape method. It is observed that the glow peak intensity increases with increase of gamma dose without changing glow curve shape. These two characteristic properties such as TL intensity increases with gamma dose and simple glow curve structure is an indication that the synthesized ZnO nanoparticles might be used as good TL dosimeter for high temperature application.     

Bogomolov restriction theorem for Higgs bundles

Let (E,θ) be a stable Higgs bundle of rank r on a smooth complex projective surface X equipped with a polarization H. Let C⊂X be a smooth complete curve with [C]=n⋅H. If where , then we prove that the restriction of (E,θ) to C is a stable Higgs bundle. This is a Higgs bundle analog of Bogomolov's restriction theorem for stable vector bundles.     

Effects of the Low Frequencies of Noise on On–Off Intermittency

A bifurcating system subject to multiplicative noise can exhibit on–off intermittency close to the instability threshold. For a canonical system, we discuss the dependence of this intermittency on the Power Spectrum Density (PSD) of the noise. Our study is based on the calculation of the Probability Density Function (PDF) of the unstable variable. We derive analytical results for some particular types of noises and interpret them in the framework of on-off intermittency. Besides, we perform a cumulant expansion (N. G. van Kampen, 24, 171 (1976).) for a random noise with arbitrary power spectrum density and we show that the intermittent regime is controlled by the ratio between the departure from the threshold and the value of the PSD of the noise at zero frequency. Our results are in agreement with numerical simulations performed with two types of random perturbations: colored Gaussian noise and deterministic fluctuations of a chaotic variable. Extensions of this study to another, more complex, system are presented and the underlying mechanisms are discussed. PACS Number: 05.40.-a, 05.45.-a, 91.25.-r     

Electronic absorption spectra of 1,2,3-trimethyl benzene

The electronic absorption spectra of 1,2,3-trimethyl benzene in the vapour and solid phases and in an isobutyl alcohol rigid glass at 90°K are described in this paper. Some characteristic features of the vibrational structure of the spectra are discussed.     

Intensification of the reaction between Udaipur rock phosphate and sulphuric acid by means of ultrasound

The solid-liquid reaction between Udaipur rock phosphate and different concentrations of sulphuric acid is found to be greatly enhanced when the reaction is carried out in the presence of high intensity ultrasound (800 kHz and 80 W cm^?2). Even coarser rock particles up to 50 mesh (BSS) can be effectively decomposed in the presence of ultrasound to such an extent that is suitable for utilization in a commercial phosphatic fertilizer plant, which is not otherwise possible. The ultrasound helps the diffusion of reactants on to the solid rock particles and also inhibits the coating of calcium sulphate, formed during the reaction, on the unreacted solid rock particles. The decomposition curve of Udaipur rock phosphate at 80°C with different concentrations of sulphuric acid contains two maxima and two minima which are controlled by the concentration of H₃O⁺, HSO₄^? and SO₄^2? ions in the medium as the reaction proceeds. It is found that the presence of ultrasound reduces the difference between these maxima and minima and the decomposition is increased in all cases.     

Influence of high intensity ultrasound on wet process phosphoric acid

High intensity ultrasound (800 kHz and 80 Wcm^-2) is passed through phosphoric acid of different origins and concentrations. Its influence on fluorine content, viscosity, density, colour and tendency to form sludge on ageing is observed. The quantity of fluorine in all samples of acid goes on decreasing with the time of exposure to ultrasound. Due to removal of fluorine by the ultrasound, the tendency of the acids to form sludge also decreases. The evolution of fluorine from the wet process phosphoric acid may be due to the decomposition of H₂SiF₆ present in the acid to HF and SiF₄ by the enormous amount of energy released due to cavitation. The exposed acid thus becomes purer, and can be concentrated and transported easily without sludge formation.     

Fabrication of a metal nanoparticles and polymer nanofibers composite material by an in situ chemical synthetic route

This work demonstrated a facile route for the synthesis of poly(3,5-dimethyl aniline) nanofibers by polymerization of 3,5-dimethyl aniline using Pd-acetate as the oxidant. The reduction of Pd ion is accompanied by oxidative polymerization of 3,5-dimethyl aniline, leading to a metal-polymer composite material. Palladium nanoparticles (approximately 2 nm) are uniformly distributed throughout the polymer that makes the composite material a unique morphology. The resultant composite material was characterized by means of different techniques. IR and Raman spectra provide the information on the chemical structure of the polymer. TEM images show the morphology of the polymer and size of the metal particles.