Suboxides with Complex Anions: The Suboxoindate Cs9InO4

Salty metal : In the suboxometallate Cs₉InO₄, metallic cesium columns (see picture; blue) lie next to ionic oxoindate(III) columns. The chemistry of the suboxides is thus expanded to structures containing complex anions.

     

Flow of a Maxwell fluid between two side walls induced by a constantly accelerating plate

The unsteady flow of a Maxwell fluid induced by a constantly accelerating plate between two side walls perpendicular to the plate is studied. Exact solutions for the velocity field are established by means of the Fourier sine transforms. The adequate tangential stresses are also determined. The similar solutions for a Newtonian fluid are obtained as limiting cases of our solutions. In the absence of the side walls, the similar solutions for the unsteady flow over an infinite flat plate are recovered. Finally, for comparison, the velocity field in the middle of the channel and the shear stresses at the bottom wall and on the side walls are plotted for different values of the material constants.      

Parameter motivated mutual correlation analysis: Application to the study of currency exchange rates based on intermittency parameter and Hurst exponent

We present a novel method for the parameter oriented analysis of mutual correlation between independent time series or between equivalent structures such as ordered data sets. The proposed method is based on the sliding window technique, defines a new type of correlation measure and can be applied to time series from all domains of science and technology, experimental or simulated. A specific parameter that can characterize the time series is computed for each window and a cross correlation analysis is carried out on the set of values obtained for the time series under investigation. We apply this method to the study of some currency daily exchange rates from the point of view of the Hurst exponent and the intermittency parameter. Interesting correlation relationships are revealed and a tentative crisis prediction is presented.     

Nonuniform scaling applied to surface energies of transition metals

We construct a generalized gradient approximation of the exchange-correlation energy that satisfies the nonuniform scaling in one dimension and is accurate in the whole quasi-two-dimensional (Q2D) regime. Using spatial and energetic analyses of metal (111) surfaces, we show that the Q2D behavior is important at the surface of most transition metals, and that the here proposed Q2D-generalized gradient approximation functional predicts for these metals accurate surface energies as well as bulk properties.     

Catalytic,Regioselective 1,4-Fluorodifunctionalization of Dienes

A catalysis-based regioselective 1,4-fluorofunctionalization of trifluoromethyl substituted 1,3-dienes has been developed to access compact, highly functionalized products. The process allows E,Z-mixed dienes to be processed to a single E-alkene isomer, and leverages an inexpensive and operationally convenient I(I)/I(III) catalysis platform. The first example of catalytic 1,4-difluorination is disclosed and subsequently evolved to enable 1,4-hetero-difunctionalization, which allows δ-fluoro-alcohol and amine derivatives to be forged in a single operation. The protocol is compatible with a variety of nucleophiles including fluoride, nitriles, carboxylic acids, alcohols and even water thereby allowing highly functionalized products, with a stereocenter bearing both C(sp³)−F and C(sp³)−CF₃ groups, to be generated rapidly. Scalability (up to 3 mmol), and facile post-reaction modifications are demonstrated to underscore the utility of the method in expanding organofluorine chemical space.     

Blends of a new thermoplastic in a thermoset epoxy matrix

Properties of thermoplastic modified epoxy network have been studied. The particularity of this work is the use of new thermoplastic epoxies whose structure is close to the final matrix. Blends of thermoset epoxy (Diglycidyl Ether of Bisphenol A/4-4′ methylenebis [3-chloro 2,6-diethylaniline]) with a thermoplastic content from 5 to 40%w have been realised. Initial miscibility in the thermoset precursors shows an UCST behaviour with a maximal value near 130°C for a thermoplastic content of 10%. Due to the presence of tertiary amine and pendant hydroxyl groups on the thermoplastic backbone, epoxy amine reactions are faster than for the neat system but the thermoplastic seems not to have reacted with the thermoset network. The final blends are transparent but toughening increase is rather low.     

Design of a flexible but robust setup for temperature-dependent electrochemistry down to cryogenic temperatures

Electrochemistry and its analytics are essential in a variety of scientific and technological fields where properties related to reduction-oxidation reactions, so-called redox properties, are to be explored. While methodological standards for experiments are well established at room temperature, this is still untrue at sub-zero/cryogenic temperatures, the conditions required for the survey of (ultra−)rapid processes and their intermediates. Problems due to “hand-waving” temperature regulation/conditioning and common usage of pseudo-reference electrodes renders cryo-electrochemistry a great challenge. Herein, we describe a robust setup for performing reliable cryo-electrochemical experiments down to −80 °C. It combines highly stable but flexible temperature conditioning with gas-tight sealing of the electrochemical cell setup. Modification of a commercial palladium hydride reference electrode (PdH RE) allows for rapid temperature cycling under cryogenic conditions in aprotic organic solvents. Validation of the setup with the well-known Ferrocene|Ferrocenium (Fc|Fc⁺) redox couple gave good compliance with literature data at room temperature in a range of organic solvent-based electrolytes. Evaluation of temperature-dependent diffusion kinetic parameters, such as diffusion coefficients (D) and diffusional activation energies (E_a,D) from CVs at multiple potential scan-rates and temperature levels emphasize the reliability of the presented cryo-electrochemical setup.     

Forging Medium Rings via I(I)/I(III)-Catalyzed Diene Carbofunctionalization

A main-group catalysis-based strategy to access 8-membered carbocycles via the direct carbofunctionalization of 2-phenethyl-substituted 1,3-dienes is disclosed. Through the intervention of an I(I)/I(III) catalysis cycle, the synthesis of densely functionalized, fluorinated benzocyclooctenes can be achieved in an operationally simple manner. Modulating the oxidation/activation regime, and the external nucleophile, the process has been extended to unify the challenging cyclization with formation of allylic C−O, C−N, and C−C bonds (>30 examples). Derivatization of the product benzocyclooctenes is demonstrated together with X-ray conformational analysis, preliminary validation of enantioselective catalysis and a scalable resolution protocol.