Spektroskopische Ermittlung der Wurzeln der mittleren Amplitudenquadrate einiger tetraedrischer Thioanionen und Chloroanionen von Elementen der Gruppen VA,VB, VIB,IIB und VIII des Periodensystems

Zusammenfassung Die Analyse der Struktur und des Schwingungsverhaltens einiger Thioanionen und Chloroanionen von Elementen der Gruppen VA, VB, VIB, IIB und VIII des Periodensystems, wie z. B. AsS₄ ^3–, SbS₄ ^3–, VS₄ ^3–, MoS₄ ^2–, WS₄ ^2–, HgCl₄ ^2– und FeCl₄ ^2–, wird kurz beschrieben. Diese Anionen haben reguläre tetraedrische Struktur und gehören zur Punktgruppe T_d. Auf Grund gruppentheoretischer Überlegungen werden für 298°K und 500°K die mittleren Amplitudenquadrate, die verallgemeinerten mittleren Amplitudenquadrate (die mittleren Quadrate der Parallel- und der Vertikalamplituden und die mittleren gemischten Produkte) und die Wurzeln der mittleren Amplitudenquadrate der gebundenen und der nichtgebundenen Atompaare dieser Anionen berechnet. Dazu werden in jüngster Zeit erhaltene Werte des Schwingungsverhaltens verwendet. Das Verhalten der Wurzeln der mittleren Amplitudenquadrate der gebundenen und der nichtgebundenen Atompaare wird auf Grund der Elektronegativitäten der Zentralatome erklärt. Es folgt eine Diskussion der Ergebnisse hinsichtlich der chemischen Bedeutung der charakteristischen Bindungen in allen behandelten Thioanionen und Chloroanionen.

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Spectroscopic studies of root-mean-square amplitudes for some tetrahedral thioanions and chloroanions of groups VA, VB, VIB, IIB, and VIII elements

The vibrational and structural analysis of a few thioanions and chloroanions of groups VA, VB, VIB, IIB, and VIII elements, such as AsS₄ ^3–, SbS₄ ^3–, VS₄ ^3–, MoS₄ ^2–, WS₄ ^2–, HgCl₄ ^2–, and FeCl₄ ^2– is briefly described. These anions have a regular tetrahedral structure with the symmetry point group T_d. On the basis of group theoretical considerations, the mean-square amplitudes, the generalized mean-square amplitudes (mean-square parallel amplitudes, mean-square perpendicular amplitudes, and mean cross products), and the root-mean-square amplitudes for both bonded and nonbonded atom pairs have been evaluated for these anions at the temperatures 298°K and 500°K by making use of the recent vibrational data. The behaviour of the root-mean-square amplitudes for both bonded and nonbonded atom pairs has been explained in terms of the electronegativities of the central atoms. A discussion of the results follows on the chemical significance of the characteristic bonds for all the thioanions and chloroanions.

     

Virtual screening for binding of phenylalanine analogues to phenylalanyl-tRNA synthetase

Although incorporation of nonnatural amino acids provides a powerful means of controlling protein structure and function, experimental investigations of amino acid analogues for utilization by the protein biosynthetic machinery can be costly and time-consuming. In this paper, we describe a computational protocol (HierDock) for predicting the relative energies of binding of phenylalanine analogues to phenylalanyl-tRNA synthetase (PheRS). Starting with the crystal structure of Thermus thermophilus PheRS without bound ligand, HierDock predicts the binding site of phenylalanine (Phe) within 1.1 A of that revealed by the crystal structure of PheRS cocrystallized with Phe. The calculated binding energies of Phe analogues in PheRS, using HierDock, correlate well with the translational activities of the same analogues in Escherichia coli. HierDock identifies p-fluorophenylalanine and 3-thienylalanine as especially good substrates for PheRS, in agreement with experiment. These results suggest that the HierDock protocol may be useful for virtual screening of amino acid analogues prior to experiment.     

In-situ formation of 2H phase MoS2/cerium-zirconium oxide nanohybrid for potential electrochemical detection of an anticancer drug flutamide

The developing field of sensors is highly motivated and attracted by two-dimensional transition metal dichalcogenides (TMDs) with transition metal oxide integration. Initially, molybdenum disulfide (MoS₂), one among the TMDs with cerium-zirconium oxide (CZO), was one-pot synthesized via hydrothermal method for sensing flutamide (FLD). The as-synthesized hybrid nanocomposite was characterized to understand their physical and chemical presence. MoS₂-CZO was well assigned with crystalline nature observed from X-ray powder diffraction and X-ray photoelectron spectroscopy. High-resolution transmission electron microscopy confirms the irregularly arranged nanoparticles wrapped with MoS₂ sheets. The wide surface area with more electroactive sites has provided higher conductance of the MoS₂-CZO/glassy carbon electrode. The limit of detection was 0.005 μM with a linear range of 0.019 μM to 668.5 μM, sensitivity 0.353 μA μM?1 cm^?2. The practical feasibility was analyzed with human urine and river water samples, whereas the obtained results showed excellent FLD detection. The fabricated MoS₂-CZO with all these distinguished analyses will be an outbreak in the field of electrochemical sensors.     

A distorted cubic tetranuclear copper(II) phosphonate cage with a double-four-ring-type core

The reaction of Cu2(O2CMe)(4).2H2O with tert-butylphosphonic acid and 3,5-di-tert-butylpyrazole in the presence of triethylamine leads to a high-yield synthesis of the tetranuclear compound [Cu2(3,5-t-Bu2PzH)2(t-BuPO3)2]2 (1). The latter has a distorted cubic cage structure and its core resembles the D4R (double-four-ring) motif found in zeolites. The phosphonate, [t-BuPO3]2-, functions as a dianionic tridentate ligand, while the pyrazole ligands are neutral and are monodentate. The coordination geometry at each copper atom is distorted square planar with a 3O,1N coordination environment. Magnetic measurements on 1 reveal that the chiT product continuously decreases to reach a value very close to zero at 1.8 K, indicating dominant antiferromagnetic interactions between Cu(II) ions that leads to an S=0 ground state. The tetranuclear cage 1 functions as a very effective artificial nuclease in the presence of an external oxidant, magnesium monoperoxyphthalate.     

Merging Copper(I) Photoredox Catalysis and Iodine(III) Chemistry for the Oxy-monofluoromethylation of Alkenes

A simple process for the oxy-monofluoromethylation of alkenes is described. In combination with visible-light copper(I) photoredox catalysis, an easily accessible iodine(III) reagent containing monofluoroacetoxy ligands serves as a powerful source of a monofluoromethyl (CH₂F) radical, enabling the step economical synthesis of γ-fluoro-acetates from a broad range of olefinic substrates under mild conditions. Applications to late-stage diversification of alkenes derived from complex molecules, amino acids and the synthesis of fluoromethylated heterocycles are also demonstrated.     

Stationary,completely mixed and symmetric optimal and equilibrium strategies in stochastic games

In this paper, we address various types of two-person stochastic games—both zero-sum and nonzero-sum, discounted and undiscounted. In particular, we address different aspects of stochastic games, namely: (1) When is a two-person stochastic game completely mixed? (2) Can we identify classes of undiscounted zero-sum stochastic games that have stationary optimal strategies? (3) When does a two-person stochastic game possess symmetric optimal/equilibrium strategies? Firstly, we provide some necessary and some sufficient conditions under which certain classes of discounted and undiscounted stochastic games are completely mixed. In particular, we show that, if a discounted zero-sum switching control stochastic game with symmetric payoff matrices has a completely mixed stationary optimal strategy, then the stochastic game is completely mixed if and only if the matrix games restricted to states are all completely mixed. Secondly, we identify certain classes of undiscounted zero-sum stochastic games that have stationary optima under specific conditions for individual payoff matrices and transition probabilities. Thirdly, we provide sufficient conditions for discounted as well as certain classes of undiscounted stochastic games to have symmetric optimal/equilibrium strategies—namely, transitions are symmetric and the payoff matrices of one player are the transpose of those of the other. We also provide a sufficient condition for the stochastic game to have a symmetric pure strategy equilibrium. We also provide examples to show the sharpness of our results.     

Experimental and Theoretical Studies of 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine: A Potential Antibacterial Agent

The title compound ( 1 ), 4‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazol‐4‐yl)‐6‐(2,4‐dichlorophenyl)pyrimidin‐2‐amine (C₂₀H₁₆Cl₂N₆), was synthesized and structurally characterized by elemental analysis, ¹H NMR and ¹³C NMR and single crystal X‐ray diffraction. The compound crystallizes as a colourless needle shaped in the triclinic system, space group P‐1 with cell constants: a = 10.7557(11) Å, b = 12.7078(17) Å, c = 15.511(2) Å, α = 68.029(4)0, β = 86.637(5)0, γ = 87.869(4)0; V = 1962.4 (4) ų, Z = 4. There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, which is linked via N‐H…Cl hydrogen bond. An intramolecular C‐H…N hydrogen also occurs in each molecule. In the crystal, each of independent molecules forms a centrosymmetric dimer with an R²₂(8) ring motifs through a pair of N‐H…N hydrogen bonds. These dimers are further connected by intermolecular N‐H…Cl and C‐H…Cl hydrogen bonds, forming an infinite two dimensional supramolecular network lying parallel to the [010] plane. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6‐311G (d, p) basis set and compared with the experimental data. Mulliken population analyses on atomic charges, HOMO‐LUMO energy levels, Molecular electrostatic potential and chemical reactivity of the title compound were investigated by theoretical calculations. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. The in vitro antibacterial activity has been screened against Gram‐positive (Bacillus cerus and Staphylococcus epidermidis) and Gram‐Negative (Escherichia coli, Acinetobacter baumannii and Proteus vulgaris). The results revealed that the compound exhibited good to moderate antibacterial activity.     

Heavy electron YBNi2B2C and giant exchange YbNiBC: 170Yb Mössbauer spectroscopy and magnetization studies

We present magnetic properties of the three-band Hubbard model in the para- and antiferromagnetic phase on a hypercubic lattice calculated with the Dynamical Mean-Field Theory (DMFT). To allow for solutions with broken spin-symmetry we extended the approach to lattices with AB-like structure. Above a critical sublattice magnetization one can observe rich structures in the spectral-functions similar to the t-J model which can be related to the well known bound states for one hole in the Neél-background. In addition to the one-particle properties we discuss the static spin-susceptibility in the paramagnetic state at the points and for different dopings . The -T-phase-diagram exhibits an enhanced stability of the antiferromagnetic state for electron-doped systems in comparison to hole-doped. This asymmetry in the phase diagram is in qualitative agreement with experiments for high-T_c materials. Received: 28 May 1998 / Revised and Accepted: 14 September 1998