Method of measurements with random perturbation: Application in photoemission experiments

We report an application of a simultaneous perturbation stochastic approximation (SPSA) algorithm to filtering systematic noise (SN) with non-zero mean value in photoemission data. In our analysis we have used a series of 50 single-scan photoemission spectra of W(110) surface where randomly chosen SN was added. It was found that the SPSA-evaluated spectrum is in good agreement with the spectrum measured without SN. On the basis of our results a wide application of SPSA for evaluation of experimental data is anticipated.Comment: 11 pages, 3 figure

Heterogeneous bromination of alkenes using Bi(III) polybromide complexes as {Br<inf>2</inf>} source

© 2016 The Royal Society of Chemistry.A new polybromide Bi(iii) complex (PyH)3{[Bi2Br9](Br2)} was synthesized and characterized by XRD and other methods. This compound is able to act as a selective bromination agent towards various types of substituted alkenes

Crystal structures of binuclear Bi(III) chloride and bromide complexes with some cations — Alkylated pyridine derivatives

© 2017, Pleiades Publishing, Ltd. By a reaction of [BiX 6 ] 3– with salts of various N-alkylated pyridine derivatives in 2M HX (X = Cl, Br), (N-BzPy) 4 [Bi 2 X 10 ] complexes (X = Cl (1), Br (2), (4-MePyH) 4 [Bi 2 Cl 10 ] (3)) are obtained and structurally characterized

4-Hydroxy-2-pyrones: Synthesis, Natural Products, and Application

4-Hydroxy-2-pyrones are of interest as potential biorenewable molecules for a sustainable transition from biomass feedstock to valuable chemical products. This review focuses on the methodologies for the synthesis of 4-hydroxy-2-pyrones published over the last 20 years. These pyrones as polyketides are widespread in Nature and possess versatile bioactivity that makes them an attractive target for synthesis and modification. Biosynthetic paths of the pyrones are actively developed and used as biotechnological approaches for the construction of natural and unnatural polysubstituted 4-hydroxy-2-pyrones. The major synthetical methods are biomimetic and are based on the cyclization of tricarbonyl compounds. Novel chemical methods of de novo synthesis based on alkyne cyclizations using transition metal complexes and ketene transformations allow for straightforward access to 4-hydroxy-2-pyrones and have been applied for the construction of natural products. Possible directions for further pyrone ring modification are discussed. © 2023 by the authors.Russian Science Foundation, RSF: 22-73-10236This work was financially supported by the Russian Science Foundation (grant 22-73-10236, https://rscf.ru/project/22-73-10236/(accessed on 10 December 2023))

Use of the macrocyclic ligand cucurbit[6]uril for isolation of tetranuclear lanthanide aquahydroxo-carboxylate complexes from aqueous solutions

The tetranuclear lanthanide complexes {[Ln4(μ3-OH) 4(μ2-OH)2(C5NH 4COO)2 (H2O)4-(C36H 36N24O12)2][Ln(H2O) 8]1.5[Ln(H2O)6(NO3) 2]0.5} (NO3)9•nH2O (Ln = Ho, Gd, or Er) were prepared by heating (130 °C) aqueous solutions of lanthanide nitrates, cucurbit[6]uril (C36H36N 24O12), and 4-cyanopyridine. The tetradentate coordination of the macrocyclic cucurbit[6]uril ligands through the portals leads to the formation of sandwich compounds, in which the tetranuclear hydroxo complex is located between two macrocyclic molecules. The polynuclear complexes are additionally stabilized by the chelating effect of the isonicotinate ligands generated by hydrolysis of 4-cyanopyridine. In the complexes, the aromatic moiety of the isonicotinate ion is encapsulated into the hydrophobic inner cavity of cucurbit[6]uril. In the absence of cucurbit[6]uril, the reaction with 4-cyanopyridine produces only the polymeric complexes [Nd(C5NH 4COO)3(H2O)2] and [Ln(C 5NH4COO)2(H2O)4]NO 3 (Ln = Pr, Sm, or Gd), whose structures were established by X-ray diffraction. In water and aqueous solutions of nonionic and cationic surfactants, irreversible changes of the tetranuclear fragment of the complex (Ln = Gd) were observed after storage for two days, whereas the anionic surfactant stabilizes the complexes. © 2006 Springer Science+Business Media, Inc