Li8Si8, Li10Si9, and Li12Si10: Assemblies of Lithium-Silicon Aromatic Units

We report the global minima structures of Li₈Si₈, Li₁₀Si₉, and Li₁₂Si₁₀ systems, in which silicon moieties maintain structural and chemical bonding characteristics similar to those of their building blocks: the aromatic clusters T_d−Li₄Si₄ and C_2v−Li₆Si₅. Electron counting rules, chemical bonding analysis, and magnetic response properties verify the silicon unit‘s aromaticity persistence. This study demonstrates the feasibility of assembling silicon-based nanostructures from aromatics clusters as building blocks.     

Calorimetric study of spinodal decomposition in β-Cu–Al–Mn

Journal of Thermal Analysis and Calorimetry - We report data obtained from the spinodal decomposition in samples of two compositions of intermetallic Cu–Al–Mn shape memory alloys....     

Osteoarthritis subjects have differentiated lower extremity thermal skin response after the concurrent acute training session

Journal of Thermal Analysis and Calorimetry - This study investigated the thermal skin (Tsk) response of lower limbs in older adults with or without osteoarthritis before and after a concurrent...     

Oxidative dissolution of synthetic vivianites as a method for the crystallization of molecular structural motifs

Structural Chemistry - Isolation of structural motifs from minerals can be used to improve the understanding of fundamental processes such as catalytic mechanisms and spectroscopic vibrations. In...     

Isolation of a 16π-Electrons 1,4-Diphosphinine-1,4-diide with a Planar C4P2 Ring

Herein, we report the first 1,4-diphosphinine-1,4-diide compound [(ADC^Ph)P]₂ ( 5-Ph ) (ADC^Ph=PhC{(NDipp)C}₂; Dipp=2,6-iPr₂C₆H₃) derived from an anionic dicarbene (ADC^Ph) as a red crystalline solid. Compound 5-Ph containing a 16π-electron planar fused-tricyclic ring system was obtained by the 4e reduction of [(ADC^Ph)PCl₂]₂ ( 4-Ph ) with Mg (or KC₈) in a quantitative yield. Experimental and computational results imply that the central 8π-electrons C₄P₂ ring of 5-Ph , which is fused between two 6π-electrons C₃N₂ aromatic rings, is antiaromatic. Thus, each of the phosphorus atoms of 5-Ph has two electron-lone-pairs, one in a p-type orbital is in conjugation with the C=C bonds of the C₄P₂ ring, while the second resides in a σ-symmetric orbital. This can be shown with the gold complex [(ADC^Ph)P(AuCl)₂]₂ ( 6-Ph ) obtained by reacting 5-Ph with (Me₂S)AuCl. A mixture of 5-Ph and 4-Ph undergoes comproportionation in the presence of MgCl₂ to form the intermediate oxidation state compound [(ADC^Ar)P]₂(MgCl₄) ( 7-Ph ), which is an aromatic species.     

Simple functionalization of cellulose beads with pre-propargylated chitosan for clickable scaffold substrates

Concerning the increased market for bio-based materials and environmentally safe practices, cellulose-based beads are one of the more attractive alternatives. Thus, this work focuses on the generation of functional cellulose-based beads with a relatively simple and direct method of blending a pre-modified chitosan bearing the targeted functional groups and cellulose, prior to the formation of the beads, as a mean to have functional groups in the formed structure. To this end, chitosan was chemically modified with propargyl bromide in homogenous reaction conditions and then combined with cellulose in sodium hydroxide/urea solution and coagulated in nitric acid to produce spherical shaped beads. The successful chemical modification of chitosan was assessed by elemental analysis, as well as by Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The alkynyl moieties from the chitosan derivative, served as reactive functional groups for click-chemistry as demonstrated by the tagging of the commercial fluorophore Azide-Fluor 488 via CuI-catalysed alkyne-azide cycloaddition reaction, in aqueous media. This work demonstrates the one-step processing of multiple polysaccharides for functional spherical beads as a template for bio-based scaffolds such as enzyme immobilization for stimuli-response applications and bioconjugations.

     

Homogeneous and unimolecular gas‐phase thermal decomposition kinetics of methyl benzoylformate: experimental and theoretical study

The kinetics of the gas‐phase thermal decomposition of the α‐ketoester methyl benzoylformate was carried out in a static system with reaction vessel deactivated with allyl bromide, and in the presence of the free radical inhibitor propene. The rate coefficients were determined over the temperature range of 440–481 °C and pressures from 32 to 80 Torr. The reaction was found to be homogenous, unimolecular and obey a first‐order rate law. The products are methyl benzoate and CO. The temperature dependence of the rate coefficient gives the following Arrhenius parameters: log₁₀ k (s^?1) = 13.56 ± 0.31 and E_a (kJ mol^?1) = 232.6 ± 4.4. Theoretical calculations of the kinetic and thermodynamic parameters are in good agreement with the experimental values using PBE1PBE/6‐311++g(d,p). A theoretical Arrhenius plot was constructed at this level of theory, and the good agreement with the experimental Arrhenius plot suggests that this model of transition state may describe reasonably the elimination process. These results suggest a concerted non‐synchronous semi‐polar three‐membered cyclic transition state type of mechanism. The most advanced coordinate is the bond breaking C^δ+‐‐‐^δ‐OCH₃ with an evolution of 66.7%, implying this as the limiting factor of the elimination process. Copyright © 2014 John Wiley & Sons, Ltd.     

Gas‐phase elimination kinetics of selected aliphatic α,β‐unsaturated aldehydes catalyzed by hydrogen chloride

The gas‐phase elimination of 2‐methyl‐2‐propenal catalyzed by HCl yields propene and CO gas, while E‐2‐pentenal with the same catalyst gives butene and CO gas. The kinetics determinations were carried out in a static system with the reaction vessels deactivated with allyl bromide and the presence of the free radical inhibitor toluene. Temperature and pressure ranges were 350.0–410.0 °C and 34–76 Torr. The elimination reactions are homogeneous and unimolecular, and follow a first‐order rate law. The rate coefficients for the reactions are expressible by the following Arrhenius equations: Data from the kinetic and thermodynamic parameters of these catalyzed elimination reactions implies a mechanism of a concerted five‐membered cyclic transition state structure for the formation of the corresponding olefin and carbon monoxide. Copyright © 2015 John Wiley & Sons, Ltd.     

Water‐Stable Zirconium‐Based Metal–Organic Framework Material with High‐Surface Area and Gas‐Storage Capacities

We designed, synthesized, and characterized a new Zr‐based metal–organic framework material, NU‐1100 , with a pore volume of 1.53 ccg^?1 and Brunauer–Emmett–Teller (BET) surface area of 4020 m²g^?1; to our knowledge, currently the highest published for Zr‐based MOFs. CH₄/CO₂/H₂ adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g^?1, which corresponds to 43 g L^?1. The volumetric and gravimetric methane‐storage capacities at 65 bar and 298 K are approximately 180 v_STP/v and 0.27 g g^?1, respectively.