Improved Method for Preparation of 3-(1H-Indol-3-yl)benzofuran-2(3H)-ones

3-(1H-Indol-3-yl)benzofuran-2(3H)-ones were efficiently accessed via polyphosphoric acid-mediated condensation of 3-(2-nitrovinyl)-1H-indoles with phenols.     

Density Functional Theory Approach to the Vibrational Properties and Magnetic Specific Heat of the Covalent Chain Antiferromagnet KFeS2

Ternary potassium-iron sulfide, KFeS₂, belongs to the family of highly anisotropic quasi-one-dimensional antiferromagnets with unusual “anti-Curie–Weiss” susceptibility, quasi-linearly growing with a rising temperature up to 700 K, an almost vanishing magnetic contribution to the specific heat, drastically reduced magnetic moment, etc. While some of the measurements can be satisfactorily described, the deficiency of the entropy changes upon the magnetic transition and the spin state of the iron ion remains a challenge for the further understanding of magnetism. In this work, high-quality single-crystalline samples of KFeS₂ were grown by the Bridgman method, and their stoichiometry, crystal structure, and absence of alien magnetic phases were checked, utilizing wave-length dispersive X-ray electron-probe microanalysis, powder X-ray diffraction, and ⁵⁷Fe Mössbauer spectroscopy, respectively. An ab initio approach was developed to calculate the thermodynamic properties of KFeS₂. The element-specific phonon modes and their density of states (PDOS) were calculated applying the density functional theory in the DFT + U version, which explicitly takes into account the on-site Coulomb repulsion U of electrons and their exchange interaction J. The necessary calibration of the frequency scale was carried out by comparison with the experimental iron PDOS derived from the inelastic nuclear scattering experiment. The infrared absorption measurements confirmed the presence of two high-frequency peaks consistent with the calculated PDOS. The calibrated PDOS allowed the calculation of the lattice contribution to the specific heat of KFeS₂ by direct summation over the phonon modes without approximations and adjustable parameters. The temperature-dependent magnetic specific heat evaluated by subtraction of the calculated phonon contribution from the experimental specific heat provides a lower boundary for estimating the reduced spin state of the iron ion.     

Chemical and electrochemical synthesis,structure, photoluminescent properties,and biological activity of 4-methyl-N-[2-[(Z)-2-(2-pyridyl)alkyliminomethyl]phenyl]benzenesulfamide zinc(II) complexes

A series of Zn(II) complexes of the tridentate azomethine ligands, condensation products of 2-(N-tosylamino)benzaldehyde and 2-aminoalkylpyridines, were synthesized by chemical and electrochemical methods. All compounds were characterized on the basis of C, H, N elemental analysis, Fourier-transform infrared, ¹H nuclear magnetic resonance, UV–Vis, and photoluminescence studies. The local atomic structures of complexes were determined from analysis of extended X-ray absorption fine structure and X-ray absorption near-edge structure of Zn K-edges. The molecular structure of chloro-{4-methyl-N-[2-[(Z)-2-pyridyl)ethyliminomethyl]phenyl]benzenesulfamide}zinc(II) was determined by X-ray single-crystal diffraction. The fluorescence spectra show that these complexes in dimethyl sulfoxide solutions at room temperature emit bright blue luminescence at 435–461 nm with fluorescence quantum yields in the range of 0.20–0.31. The assignment and the nature of the bands in experimental UV–Vis spectra of complexes were analyzed using time-dependent density functional theory calculations B3LYP/6-31G(d). The azomethines and complexes of zinc have been screened for their antibacterial, protistocidal, and fungistatic activities against Penicillium italicum, Colpoda steinii, Escherichia coli 078, and Staphylococcus aureus P-209, and the results are compared with the activity of furazolidone, chloroquine, and Fundazol.     

Synthesis and thermodynamic functions of barium cerate co-doped with erbium and indium

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Influence of the Potential-Well Depth on the Reflection of Deuterium Atoms from the Surface of Tungsten

The dependence of the reflection coefficient on the form of the atom—surface interaction potential for the D—W system was found. Potentials with different potential well depths were considered. Calculations were carried out by simulating projectile trajectories and in the binary collision approximation.     

Different Regimes of Ultrashort Pulse Propagation in Disordered Layered Media with Resonant Loss and Gain

Different optical nanostructures containing both loss and gain components attract ever‐increasing attention as novel advanced materials and building blocks for a variety of nanophotonic and plasmonic applications. Unique tunable optical signatures of the so‐called active metamaterials support their utilization for sensing, imaging, and signal processing on micro‐ and nanoscales. However, this tunability requires flexible control over the metamaterial parameters, which could be provided by involving a set of nonlinear interactions. In this paper, a method of governing ultrashort pulses is proposed by varying the level of a population difference disorder in a random active metamaterial. This enables us to deliver three different interaction regimes: self‐induced transparency (low disorder), localization regime (moderate disorder), and light amplification (strong disorder) corresponding to strongly different light pulse speeds. Since this control could be realized via rather plain tools, like simple pump tuning, the proposed disordered medium opens a room of opportunities for designing a peculiar active component for a whole set of highly demanded optical applications.     

New chromophores based on 2-(4-vinylchromen-2-ylidene)malononitrile and 2-(2-vinylchromen-4-ylidene)malononitrile

New derivatives of 2-(4-vinylchromen-2-ylidene)malononitrile and 2-(2-vinylchromen-4-ylidene)malononitrile were synthesized using the Knoevenagel reaction of 2-(4-methyl-chromen-2-ylidene)malononitrile and 2-(2-methylchromen-4-ylidene)malononitrile, respectively, with the participation of [1-(2-n-butoxyethyl)-2,2,4,7-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)]-carbaldehyde. First hyperpolarizability (β) was calculated for the obtained compounds using the M05-2X functional and 6-31+G (d) basis. Optical properties and solvatochromism in solvents of different polarity (toluene, 1,4-dioxane, chlorobenzene, dichloromethane, DMF, and ethanol) were also investigated.

     

Point defects patterning in irradiated α-zirconium: numerical study in the framework of the rate theory

We study point defects patterning in irradiated α-zirconium numerically. In our consideration, we exploit reaction-rate theory by taking into account sink density dynamics and a change in internal stress fields due to the presence of defects. Dynamics of defect populations are studied at different irradiation conditions. It is found that point defects patterning is accompanied by a formation of vacancy clusters; their morphology change is governed by irradiation temperature and damage rate. By using statistical analysis of spatially distributed vacancy clusters, it was shown that the characteristic size of these clusters is of several nanometers. Vacancy clusters' occupation densities and distributions over their sizes are studied in detail.     

LixV2O5 nanobelts for high capacity lithium-ion battery cathodes

5–10 μm long, typically 200–300 nm wide, and several nanometers thick Li_xV₂O₅ (× ～ 0.8) nanobelts with the δ-type crystal structure were synthesized by a hydrothermal treatment of Li⁺-exchanged V₂O₅ gel. When dried at 200 °C under vacuum prior to electrochemical testing, the as-prepared nanobelts underwent the well-known δ → ε → γ-phase transition giving a mixture of ε and γ phases as a nanocomposite electrode material. Such a simple preparation procedure guarantees a yield of material with drastically enhanced initial discharge specific capacity of 490 mAh/g and great cyclability. The enhanced electrochemical performance is attributed to the complex of experimental procedures including post-synthesis treatment of the single-crystalline Li_xV₂O₅ nanobelts.     

Communication: κ-dynamics--an exact method for accelerating rare event classical molecular dynamics

κ-dynamics is an accelerated molecular dynamics method for systems with slow transitions between stable states. Short trajectories are integrated from a transition state separating a reactant state from products. The first trajectory found that leads directly to a product without recrossing the transition state and starts in the reactant state is followed. The transition time is drawn from a distribution given by the transition state theory rate and the number of attempted trajectories. Repeating this procedure from each state visited gives a statistically exact state-to-state trajectory.