Stochastic effects at ripple formation processes in anisotropic systems with multiplicative noise

We study pattern formation processes in anisotropic system governed by the Kuramoto-Sivashinsky equation with multiplicative noise as a generalization of the Bradley-Harper model for ripple formation induced by ion bombardment. For both linear and nonlinear systems we study noise induced effects at ripple formation and discuss scaling behavior of the surface growth and roughness characteristics. It was found that the secondary parameters of the ion beam (beam profile and variations of an incidence angle) can crucially change the topology of patterns and the corresponding dynamics

Solvent-modulated Binding Selectivity of Reaction Substrates to Onium-based Sigma-Hole Donors

The combination of experimental data and results of DFT calculations indicates that the catalytic activity of chalconium and halonium salts serving as sigma-hole donating organocatalysts cannot be clearly estimated via analysis of the electrostatic potential on the catalysts’ sigma-holes and values of the catalyst•••TS intermolecular interactions, such as polarization effects, charge transfer, or covalency of bonding. Moreover, the real catalytic effect might not correlate well with the values of Gibbs free energy of activation of the reactions, because solvation effects and other competitive binding processes play at least an equal or even more important role in the catalysis. It was shown in the present work that the solvation can either lead to the increase of equilibrium concentration of reactive catalyst•••electrophile associates, thus accelerating the reaction, or brings favorable generation of catalyst•••nucleophile species resulting in the suppression of the catalytic activity of the organocatalyst

Cooperativity between the Silver(I) and Iodine(III) Centers in Electrophilic Activation of Organic Substrates

Kinetic data and computational study indicate that in the solution, pyrazole-containing iodolium salts and silver(I) center bind each other, and such interplay significantly affect the total catalytic activity of mixture of these Lewis acids compared with separate catalysis of the reactions required electrophilic activation of carbonyl, imino group, or triple CC bond. Moreover, the kinetic data and 1H NMR monitoring indicate that such cooperation results in prevention of decomposition of the organocatalysts by the silver(I) center during the reaction progress. XRD study indicates that in the solid state, the iodolium triflates and silver(I) triflate associate each other to give the complex species featuring triflate-bridged iodine(III) and silver(I) centers: a rare example of square-planar silver(I) complex and pentacoordinated trigonal bipyramidal dinuclear silver(I) complex

Structure-Directing Weak Interactions with 1,4-Diiodotetrafluorobenzene Convert One-Dimensional Arrays of [M^II(acac)₂] Species into Three-Dimensional Networks

The complexes [M^II(acac)₂] (M = Cu <b>1</b>, Pd <b>2</b>, Pt <b>3</b>; Hacac = acetylacetone) and 1,4-diiodotetrafluorobenzene (FIB) were cocrystallized in CHCl₃–MeOH solutions to form adducts (<b>1</b>–<b>3</b>)·FIB, whose structures were studied by X-ray diffraction. The association leads to unification of the three structures, thus demonstrating the potential of the isostructural Cu/Pd/Pt exchange for construction of supramolecular systems involving [M^II(acac)₂] complexes. In the crystal structures of (<b>1</b>–<b>3</b>)·FIB, the intermolecular bifurcated halogen bonding I···μ₂-(O,O) and noncovalent interactions M···C were identified and then studied by density functional theory calculations and topological analysis of the electron density distribution within the framework of the QTAIM method at the M06/DZP-DKH level of theory. Apart from these unconventional interactions, two types of classic hydrogen bonding, viz. the C–H···I–C and C–H···F–C contacts between Me groups and halogen atoms of FIB, were detected. Collectively all these noncovalent structure-directing interactions provide conversion of one-dimensional arrays of the [M^II(acac)₂] species into three-dimensional networks

On polygonal measures with vanishing harmonic moments

In this note we show the existence of large families of signed polygonal measures having all harmonic moments vanishing, where by a polygonal measures we understand a signed measure supported on a finite collection of disjoint polygons and having constant real density in each of them

Nucleophilicity of Oximes Based upon Addition to a Nitrilium <i>closo</i>-Decaborate Cluster

Three types of oxime species, i.e., 4-morpholyl­carb­ami­doxime (hydroxy­guanidine), phenyl­acet­amidoxime and benzamidoxime (amidoximes), and cyclo­hexanone oxime and benzo­phenone oxime (ketoximes), react at room temperature with the 2-nitrilium <i>closo</i>-decaborate clusters, leading to 2-iminium <i>closo</i>-decaborates (14 examples; 57–94%). These species were characterized by ICPMS-based boron elemental analysis, HRESI^–-MS, molar conductivity, IR, ¹H­{¹¹B}, and ¹¹B­{¹H} NMR spectroscopies, and additionally by single-crystal X-ray diffraction (for six compounds). On the basis of kinetic data, Δ<i>H</i>^⧧, Δ<i>S</i>^⧧, and Δ<i>G</i>^⧧ of the additions were determined, showing a 4 order-of-magnitude decrease in reactivity from the hydroxy­guanidine to the aromatic ketoxime as entering nucleophiles. The results of DFT calculations indicate that the mechanism for these reactions is stepwise and is realized through the formation of the orientation complex of the nitrone form, R²R³CN⁺­(H)­O^–, of oximes with [B₁₀H₉­NCEt]⁻, giving further an acyclic intermediate (the rate-determining step), followed by proton migration, leading to the addition product. The calculated overall activation barrier for these transformations is consistent with the experimental kinetic observations. This work provides, for the first time, a broad nucleophilicity series of oximes, which is useful to control various nucleophilic additions of oxime species

Nucleophilicity of Oximes Based upon Addition to a Nitrilium <i>closo</i>-Decaborate Cluster

Three types of oxime species, i.e., 4-morpholyl­carb­ami­doxime (hydroxy­guanidine), phenyl­acet­amidoxime and benzamidoxime (amidoximes), and cyclo­hexanone oxime and benzo­phenone oxime (ketoximes), react at room temperature with the 2-nitrilium <i>closo</i>-decaborate clusters, leading to 2-iminium <i>closo</i>-decaborates (14 examples; 57–94%). These species were characterized by ICPMS-based boron elemental analysis, HRESI^–-MS, molar conductivity, IR, ¹H­{¹¹B}, and ¹¹B­{¹H} NMR spectroscopies, and additionally by single-crystal X-ray diffraction (for six compounds). On the basis of kinetic data, Δ<i>H</i>^⧧, Δ<i>S</i>^⧧, and Δ<i>G</i>^⧧ of the additions were determined, showing a 4 order-of-magnitude decrease in reactivity from the hydroxy­guanidine to the aromatic ketoxime as entering nucleophiles. The results of DFT calculations indicate that the mechanism for these reactions is stepwise and is realized through the formation of the orientation complex of the nitrone form, R²R³CN⁺­(H)­O^–, of oximes with [B₁₀H₉­NCEt]⁻, giving further an acyclic intermediate (the rate-determining step), followed by proton migration, leading to the addition product. The calculated overall activation barrier for these transformations is consistent with the experimental kinetic observations. This work provides, for the first time, a broad nucleophilicity series of oximes, which is useful to control various nucleophilic additions of oxime species