Fine-tunable monodentate phosphoroamidite and aminophosphine ligands for Rh-catalyzed asymmetric hydroformylation

A biaryl-based monophosphoroamidite L1–L4a–f and aminophosphine L5–L7a–f ligand library was screened in the Rh-catalyzed asymmetric hydroformylation of several vinylarenes and heterocyclic olefins. Our results indicate that the selectivity is strongly dependent on the ligand parameters and on the substrate type. Enantioselectivities (up to 46%) were moderate in the hydroformylation of several vinylarenes S1–S5 and promising (up to 58%) for the more challenging heterocyclic olefins S6–S9.     

Transition-metal nanoparticles in imidazolium ionic liquids: recyclable catalysts for biphasic hydrogenation reactions

1-n-Butyl-3-methylimidazolium hexafluorophosphate room-temperature ionic liquid is not only suitable as a medium for the preparation and stabilization of iridium nanoparticles but also ideal for the generation of recyclable biphasic catalytic systems for hydrogenation reactions. Thus, Ir(0) nanoparticles with a mean diameter of 2 nm have been prepared by reduction of Ir(I) dissolved in the ionic liquid with H2. This catalytic solution can be reused several times for the biphasic hydrogenation of olefins under mild reaction conditions.     

Development and comparison of two high accuracy methods for uranium concentration in nuclear fuel: ID-TIMS and K-edge densitometry

Journal of Radioanalytical and Nuclear Chemistry - We aim to recycle and utilization of eggshell as a biomass waste of human foodstuff. Pure hydroxyapatite nano-particles were prepared using waste...     

Thermal,structural and optical properties of Al2CoO4-Crocoite composite nanoparticles used as pigments

Novel zinc(II) complex compounds of general formula Zn(C₆H₅COO)₂·L₂ (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.     

Wet sol–gel silica matrices as delivery devices for phenytoin

Wet sol–gel silica matrices produced under different hydrolysis conditions were used as delivery devices to the active principle of an antiepileptic drug (phenytoin sodium), encapsulated during the condensation stage. Post-incorporation into dry silica powder was an alternative loading procedure. It was proven by infrared spectroscopy that neither the silica network nor the drug loose integrity by encapsulation. The kinetics of in vitro drug release was studied at 37 °C, to water and to artificial cerebrospinal fluid (ACSF). Emphasis has been given to the release to ACSF under dynamic conditions (with fluid renovation, emulating what occurs in the brain). Different delivery regimes were identified and correlated with the loading method and the matrix structure. Matrices with lower total porosity and smaller average pore size proved to be better for a long term release. Renovation of ACSF is relevant to assure a constant concentration of phenytoin in the vicinity of the device.     

Thermodynamic analysis of GaAs growth by molecular beam epitaxy at the surface structure transition from 3 × 1 to 4 × 2

The molecular beam epitaxy (MBE) growth of GaAs layers on a single crystal is studied in relation with the stability domain of the GaAs compound in the Ga-As binary system. The growth parameters, i.e. The Ga and As impinging atomic flows, are compared to the necessary flows as calculated by thermodynamics. In order to take into account in the real growth situation, which is not strictly at equilibrium, the flow balance at the surface of the crystal between the impinging flows and the growth and evaporated flows is written for quasi-equilibrium growth conditions, including condensation and evaporation coefficients that split the “so-called” sticking coefficient in parts related to the condensation or the evaporation phenomenon for each gaseous species. A comparison between the quasi-equilibrium simulation of the growth and the experiment is made with the assumption that the surface structure transition from gallium-stabilized to arsenic-stabilized surface corresponds to the growth of a GaAs crystal at its solidus boundary rich in gallium. The surface structure transitions are observed by reflection high energy electron diffraction (RHEED) and the impinging atomic flows are carefully calibrated and also controlled by RHEED oscillations as observed after gallium or arsenic excess as deposited on the surface. The results show that the growth is effectively performed close to equilibrium conditions as evidenced by the values of the condensations and evaporation coefficients. The evaporation coefficient of gallium is 0.4, showing that this component is the supersaturated one at the surface, and this value agrees with theoretical predictions for an evaporation process (during growth) controlled by the surface diffusion process of monoatomic species between steps.     

A new electrochemical cell adapted to quartz crystal microbalance measurements

As the resonance frequency of an oscillating quartz changes upon the deposition of a given mass to the crystal surface, it can be used as a very sensitive mass measuring device. Despite a growing interest in the use of electrochemical quartz crystal microbalance (EQCM), there is still no commercial available measurement cell which can satisfy all the conditions needed in electrochemical investigations. The design and characteristics of a new electrochemical cell adapted to EQCM measurements are presented. The sensitivity of the microbalance, which is determined by several calibration runs of silver electrodeposition is (183.2±2.9) Hz μg⁻¹ cm². This value, which is close to the theoretical one, confirms the validity of the system we have developed. The calibration procedure and the EQCM using range are then discussed.     

The structures of the α‐alums RbCr(SO4)2·12H2O and CsCr(SeO4)2·12H2O at 293 and 12 K

The crystal structures of the α‐alums rubidium chromium bis(­sulfate) dodecahydrate, RbCr(SO₄)₂·12H₂O, and caesium chromium bis[tetraoxoselenate(VI)] dodecahydrate, CsCr(SeO₄)₂·12H₂O, have been determined by X‐ray diffraction at 293 and 12 K. The metal atoms lie on sites and the anions lie on threefold rotation axes. The accurate and extensive data sets lead to much more precise determinations than are available from earlier work, particularly at 12 K. The changes in the atomic displacement parameters between 293 and 12 K correspond to the respective predominances of intermolecular and intramolecular vibrational effects.     

Cs2K[Mn(CN)6] at 293, 85 and 10 K

The crystal structure of dicaesium potassium hexacyanomanganese(III) has been determined by X‐ray diffraction at 293, 85 and 10 K. The Mn and K atoms lie on inversion centres and the Cs atom is in a general position. The accurate and extensive data sets collected should be suitable for charge–density analysis studies.