Building large supramolecular nanocapsules with europium cations

A new tripodal ligand has been designed by connecting pyridine-based coordination units to a rigid triptycene moiety. Its reaction with europium(III) provides three-dimensional tetranuclear edifices, whose structural and photophysical characteristics as well as host-guest interactions are discussed in this contribution.     

Excess Molar Volumes of Oligo(Oxyethylene Glycol) Monodecyl Ethers in n-Dodecane, and Apparent Dipole Moments of {(Oligo(Oxyethylene Glycol) Monodecyl Ethers?+?n-Heptane, n-Decane or n-Dodecane} at T?=?298.15?K

Excess molar volumes and relative permittivities at a frequency of 30?kHz of oligo(oxyethylene glycol) monodecyl ethers (C₁₀E _m ) for m?=?1?C8 in n-heptane, n-decane or n-dodecane solutions were determined for the mole fraction range 0?<?x?<?0.04 at the temperature of 298.15?K. By using Frohlich??s equation the apparent dipole moments, ??, of C₁₀E _m were calculated, and the limiting values, ?? ₀, were determined by extrapolating to infinite dilution. The values of ?? ₀ increase linearly with increasing number of oxyethylene units (m) of oligo(oxyethylene glycol) monodecyl ethers in the range m?=?2?C8, while ?? ₀ of C₁₀E₁ is less than its extrapolated value. By comparing the present results with our previous ones measured in n-heptane and decane, a solvent effect on ?? ₀ was found. The excess partial molar volumes of oligo(oxyethylene glycol) monodecyl ethers at infinite dilution increase with increasing m. Those results are discussed from the viewpoint of the interactions between oligo(oxyethylene glycol) monodecyl ethers and solvent molecules.     

Synthesis and properties of <Emphasis Type="Italic">trans</Emphasis>-2-[2-(2-hetaryl)vinyl]benzothiazoles

Electrophilic substitution reactions (formylation and acylation) in the series of 2-[2-(2-furyl)vinyl]- and 2-[2-(2-thienyl)vinyl]benzothiazoles leads to the corresponding derivatives at the α-position of the furan or thiophene ring. The presence of a vinylene bridge weakens deshielding effect of the benzothiazole fragment on π-excessive heterocycles, so that such compounds react at a higher rate and under milder conditions as compared to hetarylbenzothiazoles having no vinylene bridge.     

Instabilities and bifurcations due to buoyancy in a cylindrical container heated from below with and without a free surface

Three-dimensional simulations of the buoyant convection in a cylindrical container heated from below are presented. Both the thresholds for the onset of the convection and the nonlinear evolution of this convection are calculated. The simulations concern two configurations: a cavity with a rigid upper surface (Rigid-Rigid case) and a cavity with a non-constrained free surface (Rigid-Free case). The results show a similar variation of the primary thresholds with the aspect ratio for the two configurations. In contrast, the nonlinear evolution of the convection is much changed between the two configurations. In particular, subcritical secondary branches with a very large subcriticity are obtained in the R-F case. To cite this article: A. El Gallaf et al., C. R. Mecanique 337 (2009).     

Complexes of Low Oxidized 99Tc and Re with Thiosalicylic Acid and Their Characterization in Solution with Some CNDO-MO Calculations

Complexation of technetium-99 and rhenium in low oxidized forms with thiosalicylic acid (TSA) were investigated by uv.-vis. spectrophotometry and HPL-chromatography.

By CNDO-MO calculations of the proper structure of TSA, the charge densities, ionization potential, electron affinity and its dipole moment were studied. The violet solútions of the Tc and Re complexes exhibit characteristic bands in the visible at 420,590 nm and 410,570 nm respectively. Comparative HPLC studies using MeOH/H₂O as a mobile phase indicate the Re-TSA complex to be less stable than the Tc-TSA complex.     

Retention of β blockers on native titania stationary phase

In recent years, metal oxides such as titania have been commercially available as chromatographic beds that can potentially be used to achieve novel separations of polar compounds. For example β blockers, which are more often encountered in environmental sciences, have a wide range of polarity, and their basic character leads to difficult sample treatment and separation on conventional silica‐based sorbents. The contribution of titania to the selective analysis of nine β blockers was evaluated in terms of retention mechanisms observed in hydrophilic interaction LC using acetonitrile/water mobile phases with various additives. The mobile phase additives enabled to control the β blocker charge as well as the titania surface charge. Depending on their respective ionic state, various retention mechanisms were identified at low water contents (<40%), including mainly adsorption mixed with hydrophilic interaction LC partition, ion exchange and ion exclusion. An unexpected retention was also observed for high water content and high pH, changing the selectivity of the support.     

Corrosion of gadolinium and ytterbium in LiCl-KCl melt

Corrosion of gadolinium and ytterbium in a molten eutectic mixture of lithium and potassium chlorides is studied in the present work using the gravimetry and EMF methods. It is found that the corrosion rate of ytterbium is 3–5 times higher than that of gadolinium under similar conditions. Satisfactory agreement between the current density values of gadolinium corrosion calculated on the basis of the results of the gravimetric data and the values of steady-state potentials points to the electrochemical mechanism of gadolinium corrosion in the LiCl-KCl melt.