Chemical dynamics of the CH(X2Π) + C2H4(X1A1g), CH(X2Π) + C2D4(X1A1g), and CD(X2Π) + C2H4(X1A1g) reactions studied under single collision conditions

The crossed beam reactions of the methylidyne radical with ethylene (CH(X(2)Π) + C(2)H(4)(X(1)A(1g))), methylidyne with D4-ethylene (CH(X(2)Π) + C(2)D(4)(X(1)A(1g))), and D1-methylidyne with ethylene (CD(X(2)Π) + C(2)H(4)(X(1)A(1g))) were conducted at nominal collision energies of 17-18 kJ mol(-1) to untangle the chemical dynamics involved in the formation of distinct C(3)H(4) isomers methylacetylene (CH(3)CCH), allene (H(2)CCCH(2)), and cyclopropene (c-C(3)H(4)) via C(3)H(5) intermediates. By tracing the atomic hydrogen and deuterium loss pathways, our experimental data suggest indirect scattering dynamics and an initial addition of the (D1)-methylidyne radical to the carbon-carbon double bond of the (D4)-ethylene reactant forming a cyclopropyl radical intermediate (c-C(3)H(5)/c-C(3)D(4)H/c-C(3)H(4)D). The latter was found to ring-open to the allyl radical (H(2)CCHCH(2)/D(2)CCHCD(2)/H(2)CCDCH(2)). This intermediate was found to be long lived with life times of at least five times its rotational period and decomposed via atomic hydrogen/deuterium loss from the central carbon atom (C2) to form allene via a rather loose exit transition state in an overall strongly exoergic reaction. Based on the experiments with partially deuterated reactants, no compelling evidence could be provided to support the formation of the cyclopropene and methylacetylene isomers under single collision conditions. Likewise, hydrogen/deuterium shifts in the allyl radical intermediates or an initial insertion of the (D1)-methylidyne radical into the carbon-hydrogen/deuterium bond of the (D4)-ethylene reactant were found to be-if at all-of minor importance. Our experiments propose that in hydrocarbon-rich atmospheres of planets and their moons such as Saturn's satellite Titan, the reaction of methylidyne radicals should lead predominantly to the hitherto elusive allene molecule in these reducing environments.     

He2@C60: Thoughts of the concept of a molecule and of the concept of a bond in quantum chemistry

We present a broad palette of discussions of the concepts of a molecule and a chemical bond that always lay down behind all computational modeling in quantum chemistry and of the endohedral fullerene He₂@C₆₀ in particular. For this purpose, we offer the definition of quantum chemistry as composed of three ingredients. Each of them is illustrated by its particular concept, either that of a molecule or a bond. The third, computational ingredient is tackled to resolve the bonding manifold of He₂@C₆₀ and to demonstrate that van‐der‐Waals binding of He? He is converted within He₂@C₆₀ into a stronger bond due to that C₆₀ acts as an electronic buffer and [He₂] moiety mimics a fractionally charged . Experimental fingerprints of He₂@C₆₀ are computed. © 2015 Wiley Periodicals, Inc.     

Regularity of Weak Solutions and Their Attractors for a Parabolic Feedback Control Problem

We investigate additional regularity properties of all globally defined weak solutions, their global and trajectory attractors for a class of autonomous differential inclusion with upper semi-continuous interaction function, when initial data $u_{\tau}\in L^2(\Omega)$ . The main contributions of this paper are: (i) additional regularity and new topological properties of all weak solutions of parabolic feedback control problem with upper semi-continuous interaction function, (ii) a sufficient condition for regularity of global and trajectory attractors, and (iii) new a priory estimates for all weak solutions.     

Inhomogeneous 2D linear intergrowth structures among novel Y–Cu–Mg ternary compounds with yttrium/copper equiatomic ratio

Single crystals of the Y₅Cu₅Mg₈, Y₅Cu₅Mg₁₃, Y₅Cu₅Mg₁₆ and YCuMg₄ compounds were synthesized by heating in a resistance furnace evacuated quartz vials containing Ta-crucibles with element pieces. SEM-EDXS analyses were performed to check phases composition. The structures were refined from X-ray single crystal diffraction data. Y₅Cu₅Mg₈, Y₅Cu₅Mg₁₃ and Y₅Cu₅Mg₁₆ represent new structure types: Y₅Cu₅Mg₈ – orthorhombic, Pmma, oP36, a = 2.63723(15), b = 0.40066(2), c = 0.74115(6) nm, Z = 2, wR₂ = 0.0597, 939 F² values, 60 variables; Y₅Cu₅Mg₁₃ – orthorhombic, Cmcm, oS92, a = 0.40973(2), b = 1.92794(8), c = 2.57907(11) nm, Z = 4, wR₂ = 0.1134, 1208 F² values, 75 variables; Y₅Cu₅Mg₁₆ – orthorhombic, Cmcm, oS104, a = 0.41360(8), b = 1.9239(4), c = 2.9086(6) nm, Z = 4, wR₂ = 0.0760, 1383 F² values, 84 variables. YCuMg₄ crystallizes in the TbCuMg₄ structure type (Cmmm, oS48, a = 1.35754(4), b = 2.03153(6), c = 0.39060(1) nm, Z = 8, wR₂ = 0.0401, 661 F² values, 45 variables). The crystal chemistry of these two-layer structures is comparatively discussed. Majority of novel compounds were characterized as members of inhomogeneous 2D intergrowth structure series of R₅M₅X₅, X₄ (Mg₄) and empty Mg octahedra building blocks of general formula R_5kM_5kX_{5k + 4l + m}. The common pentagonal prism derivative structural fragments around the most electropositive yttrium atoms were outlined in all these intermetallics.     

On p-norm linear discrimination

We consider a p-norm linear discrimination model that generalizes the model of Bennett and Mangasarian (1992) and reduces to a linear programming problem with p-order cone constraints. The proposed approach for handling linear programming problems with p-order cone constraints is based on reformulation of p-order cone optimization problems as second order cone programming (SOCP) problems when p is rational. Since such reformulations typically lead to SOCP problems with large numbers of second order cones, an “economical” representation that minimizes the number of second order cones is proposed. A case study illustrating the developed model on several popular data sets is conducted.     

An L-shaped method with strengthened lift-and-project cuts

Computational Management Science - Lift-and-project (L &P) cuts are well-known general 0–1 programming cuts which are typically deployed in branch-and-cut methods to solve MILP...     

Luminescence properties of pHEMA-TiO2 gels based hybrids materials

Photoluminescence (PL) of photochromic pHEMA-TiO₂ gels-based hybrids was studied by means of time- and energy-resolved spectroscopy at temperatures between 300 K and 10 K. The PL band at 485 nm is assigned to S0←T1 transition of methoxyphenol (organic molecule added to the commercial monomer hydroxyethyl methacrylate, HEMA and used as an inhibitor of spontaneous polymerisation) in the polymer environment, while the PL band at 600 nm is assigned to the self-trapped exciton onto octahedral TiO₆ site of the inorganic component. The mechanisms of the excited states population are discussed. In particular it is shown that both singlet-triplet energy transfer in methoxyphenol and methoxyphenol–TiO₂ charge transfer are strongly affected by the material composition and temperature. The hypothesis about the photoexcited holes annihilation with the trapped electrons is confirmed to be one of main mechanisms limiting the Ti³⁺ centres concentration.     

Nickel-Catalyzed Chain-Walking Cross-Electrophile Coupling of Alkyl and Aryl Halides and Olefin Hydroarylation Enabled by Electrochemical Reduction

The first electrochemical approach for nickel-catalyzed cross-electrophile coupling was developed. This method provides a novel route to 1,1-diarylalkane derivatives from simple and readily available alkyl and aryl halides in good yields and excellent regioselectivity under mild conditions. The procedure shows good tolerance for a broad variety of functional groups and both primary and secondary alkyl halides can be used. Furthermore, the reaction was successfully scaled up to the multigram scale, thus indicating potential for industrial application. Mechanistic investigation suggested the formation of a nickel hydride in the electroreductive chain-walking arylation, which led to the development of a new nickel-catalyzed hydroarylation of styrenes to provide a series of 1,1-diaryl alkanes in good yields under mild reaction conditions.     

Direct Catalytic Trifluoromethylthiolation of Boronic Acids and Alkynes Employing Electrophilic Shelf‐Stable N‐(trifluoromethylthio)phthalimide

A new and safe method for the synthesis of N‐(trifluoromethylthio)phthalimide, a convenient and shelf‐stable reagent for the direct trifluoromethylthiolation, has been developed. N‐(Trifluoromethylthio)phthalimide can be used as an electrophilic source of F₃CS⁺ and reacts readily with boronic acids and alkynes under copper catalysis. The utility of CF₃S‐containing molecules as biologically active agents, the mild reaction conditions employed, and the high tolerance of functional groups demonstrate the potential of this new methodology to be widely applied in organic synthesis as well as industrial pharmaceutical and agrochemical research and development.