Thermodynamics and Kinetics of the Complexation Reaction of Lead by Calix‐DANS4

The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix‐DANS4 are determined to optimize the geometry of the microreactor used for the flow‐injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix‐DANS4) the 1:1 Pb²⁺‐Calix‐DANS4 complex is predominantly formed with a high stability constant (log K_1:1=6.82) and a slow second‐order rate constant (k=9.4×10⁴ L mol^?1 s^?1). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h^?1 to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors.     

Lithium salts of [1,12-dialkyl-CB11Me10]- anions

We report the syntheses of several [1-R-CB(11)-Me(11)](-) and [1-R-12-R'-CB(11)-Me(10)](-) anions (R, R' = alkyl) and the solubilities of their lithium salts in cyclohexane. These solutions are of interest as Lewis acid catalysts. The new anions are not directly accessible by methylation with methyl triflate because of intervening triflyloxy substitution on one or more boron vertices. The difficulty has been circumvented in two ways. Either (i) an iodo substituent is first introduced into position 12, permitting a clean decamethylation, and then replaced with a methyl by reaction with trimethylaluminum or (ii) the offending triflyloxy substituents are replaced with methyls by reaction with trimethylaluminum.     

Microwave-assisted alkylation of [CB11H12]- and related anions

A total of 19 permethylated derivatives of substituted [CB(11)H(12)](-) anions have been prepared using alkylation with microwave assistance. The reactions proceed much faster and more cleanly than under ordinary conditions. Microwave assistance is especially convenient for the permethylation of carborane anions carrying electron-withdrawing groups in positions 1 and/or 12. Even [1-F-CB(11)H(11)](-) can be undecamethylated, whereas under ordinary heating, it has only been hexamethylated.     

Synthesis of poly(amino)ester dendrimers via active cyanomethyl ester intermediates

A novel strategy for the synthesis of poly(amino)ester dendrimers was developed on the basis of active cyanomethyl ester intermediates and an iteration of four consecutive steps of deprotection, activation, transesterification, and scavenging.     

Synthesis,Electronic Properties,and Reactivity of Phospholes and 1,1′‐Biphospholes Bearing 2‐ or 3‐Thienyl C‐Substituents

PS, I love you! Novel mixed phosphole/thiophene π‐conjugated systems were synthesized and their electronic properties have been studied both experimentally by UV/Vis spectroscopy and electrochemistry and by theoretical calculations. Exploiting the chemistry of both P‐ and S‐heteroles allows the generation of a diverse range of novel ring‐fused benzophosphole–thiophene derivatives.

     

Electron spectrum and heat capacity of heavy fermions in the canted phase of antiferromagnetic intermetallides

The energy spectrum of heavy fermions in an external magnetic field is calculated for canted magnetic sublattices of antiferromagnetic intermetallides. This makes it possible to determine low-temperature features of electronic heat capacity of heavy-fermion antiferromagnets with the metal-type ground state taking into account the structural rearrangement of the magnetic subsystem. The calculated temperature dependences of the magnetization, heat capacity, and Sommerfeld constant in the vicinity of the point of transition to the antiferromagnetic phase correlate with experimental data obtained for heavy-fermion antiferromagnets PuGa₃, Ce₂Au₂Cd, YbNiSi₃, and PuPd₅Al₂.     

DISCO: a low‐energy multipurpose beamline at synchrotron SOLEIL

DISCO, a novel low‐energy beamline covering the spectrum range from the VUV to the visible, has received its first photons at the French synchrotron SOLEIL. In this article the DISCO design and concept of three experimental stations serving research communities in biology and chemistry are described. Emphasis has been put on high flux generation and preservation of polarization at variable energy resolutions. The three experiments include a completely new approach for microscopy and atmospheric pressure experiments as well as a `classical' synchrotron radiation circular dichroism station. Preliminary tests of the optical design and technical concept have been made. Theoretical predictions of the beam have been compared with the first images produced by the first photons originating from the large‐aperture bending‐magnet source. Results are also reported concerning the cold finger used to absorb hard X‐ray radiation in the central part of the synchrotron beam and to avoid heavy thermal load on the following optics. Wavelength selection using monochromators with different gratings for each experimental set‐up as well as beam propagation and conditioning throughout the optical system are detailed. First photons comply very well with the theoretical calculations.