Tetrathiafulvalene crowns: redox-switchable ligands

A series of redox-responsive ligands that associate the electroactive tetrathiafulvalene core with polyether subunits of various lengths has been synthesized. X-ray structures are provided for each of the free ligands. The requisite structural criteria for reaching switchable ligands are satisfied for the largest macrocycles, that is, planarity of the 1,1',3,3'-tetrathiafulvalene (TTF) pi system and correctly oriented coordinating atoms. The ability of these ligands to recognize various metal cations as a function of the cavity size has been investigated by various techniques (LSIMS, 1H NMR, and UV/Vis spectroscopy, cyclic voltammetry). These systems exhibit an unprecedented high coordination ability among TTF crown ethers. Their switchable ligating properties have been confirmed by cyclic voltammetry, and metal-cation complexation has been illustrated by X-ray structures of three of the corresponding metal complexes (Pb2+, Sr2+, and Ba2+). Solid-state structures of these complexes display original packing modes with channel-like arrangements.     

Oxidation of propane over ammonium-transition metal mixed keggin phosphomolybdate salts

Mixed ammonium-transition metal salts with formula of (NH4)xMyHzPMo12O40 (M = Ni2+, Co2+ or Fe 3+) denoted as MPMo12 have been investigated for the oxidation of propane, with molecular oxygen, at temperature range between 380℃ and 420℃ after in-situ pre-treatment performed at two heating rate of 5 or 9℃/min. They were characterized by BET method, XRD, UV-Vis and IR techniques. The catalysts were found to be active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-t...     

MCNP5 evaluation of a response matrix of a Bonner Sphere Spectrometer with a high efficiency <Superscript>6</Superscript>LiI (Eu) detector from 0.01 eV to 20 MeV neutrons

A new approach has been suggested to establish reliable response matrix of a CRNA Bonner Sphere Spectrometer equipped with a high efficiency 10 mm diameter × 2 mm thick ⁶LiI (Eu) scintillation detector from thermal neutron energy up to 20 MeV. It combines the experimental response functions obtained using a continuous neutron spectrum emitted from an ²⁴¹Am-Be neutron source of known emission, with those obtained by Monte-Carlo (MC) calculations. Sensitivity analysis has been performed to check the influence of pertinent parameters on the MC computed detector response. The parameters of interest are the density of polyethylene moderators, the cross section library used in MCNP5 and two computing models depending on the interactions of the neutrons in the detector. The calculated responses of the spectrometer to the ²⁴¹Am-Be neutron source showed discrepancies depending on the sphere diameter when compared to our measured responses. However, this difference was smaller compared with the experiments available in the literature. The enhancement achieved in the present study is partly due to improved modeling in the MC calculations. To correct for the differences observed, a fitting factor has been deduced for each sphere diameter and used to adjust the MC responses to the experimental ones. The obtained results were subsequently compared to the experimental data of GSF-G spheres system obtained for a typical 4 mm diameter × 4 mm thick ⁶LiI scintillator for four ISO-8529 selected neutron energies (144.0 keV, 565 keV, 2.5 and 14.8 MeV). The present responses were similar in shape but higher, in absolute values, by about two and half times for all spheres owing essentially to the increase in active part of the detector. Finally, the CRNA-BSS response matrix containing 48 energy points from 0.01 eV to 20 MeV for 22 sphere diameters with a mean polyethylene density of 0.944 g/cm³ was constructed by applying a spline interpolation method. The released response matrix was then compared to data available in the literature evaluated by Monte-Carlo calculations for a 4 mm × 4 mm ⁶LiI crystal scintillator. The obtained response matrix is intended for radiation protection applications at CRNA.     

Comparison between Conventional and Nonconventional Methods for the Synthesis of Some 2-Oxazolidinone Derivatives and Preliminary Investigation of Their Inhibitory Activity Against Certain Protein Kinases

Russian Journal of Organic Chemistry - A series of propargyl and allyl carbamates were prepared directly from propargyl and allyl alcohols and phenyl or cyclohexyl isocyanate or indirectly by...     

Microwave-assisted synthesis of calix[4]resorcinarenes

Microwave-assisted synthesis of calix[4]resorcinarenes by cyclocondensation of various aldehydes and resorcinol catalysed by 12-tungstophosphoric acid type Keggin (H₃PW₁₂O₄₀·13H₂O) or concentrated HCl is described. Excellent isolated yields (up to 90%) were attained within short reaction times (typically, 3-5 min) when the reaction was performed under microwaves irradiation.     

Crown-tetrathiafulvalenes attached to a pyrrole or an EDOT unit: synthesis, electropolymerization and recognition properties

A crown-tetrathiafulvalene electroactive receptor has been covalently linked to electropolymerizable pyrrole or 3,4-ethylenedioxythiophene monomers. The synthetic route to the monofonctionalized tetrathiafulvalene (TTF) ligand has been optimized. Two derivatives of pyrrole (N- and 3-substituted) were synthesized. The various substituted monomers have been electropolymerized to produce polypyrrole (PP) and poly(ethylenedioxothiophene) (PEDOT) films bearing the electroactive TTF moiety. The electroactivity of the polymer films is efficiently controlled by the well-defined two-step redox behavior of the TTF unit. In the case of PEDOT, an alternative post-polymerization derivatization strategy has been used, involving the grafting of the crown-TTF ligand on the previously grown PEDOT backbone. Though chemical derivatization is realized under heterogeneous conditions, in the bulk of the film, this strategy proved to be particularly efficient. These electrodes constitute the first examples of conducting polymer-based modified electrodes incorporating a TTF electrochemical probe, able to interact with a guest ion, such as Ba2+. The cation recognition properties of these various electrodes have been analyzed by cyclic voltammetry and their electroactivity in water as well as their regeneration capability have been investigated.     

Oxidation of propane over substituted Keggin phosphomolybdate salts

Ammonium salts, (NH₄)₆HPMo₁₁MO₄₀ (M = Ni, Co, Fe), have been investigated for the oxidation of propane, with molecular oxygen, at temperature ranging between 380 °C and 420 °Cafter in-situ pre-treatment performed at two heating rate of 5 or 9 °C/min. They were characterized by BET method, XRD, ³¹P NMR, UV-Vis and IR techniques. The catalysts were found active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 °C/min.