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11.
The Use of Cobalt‐Mediated Cycloisomerisation of Ynedinitriles in the Synthesis of Pyridazinohelicenes
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Dr. Serghei Chercheja Jiří Klívar Andrej Jančařík Dr. Jiří Rybáček Simon Salzl Dr. Ján Tarábek Prof. Dr. Lubomír Pospíšil Dr. Jana Vacek Chocholoušová Dr. Jaroslav Vacek Dr. Radek Pohl Dr. Ivana Císařová Dr. Ivo Starý Dr. Irena G. Stará 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8477-8482
A cobalt‐mediated [2+2+2] cycloisomerisation of ynedinitriles to helical pyridazines in good to high yields was developed. The construction of the pyridazine nucleus from one alkyne and two nitrile units is proposed to follow either a conventional organometallic mechanism or to be triggered by a single‐electron transfer from a CoII species. Various [5]‐, [6]‐ and [7]helicene pyridazines were prepared. 相似文献
12.
Serghei N. Klimin Jacques Tempere Vyacheslav R. Misko Michiel Wouters 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(8):172
Electrons on liquid helium can form different phases depending on density, and temperature. Also the electron-ripplon coupling strength influences the phase diagram, through the formation of so-called “ripplonic polarons”, that change how electrons are localized, and that shifts the transition between the Wigner solid and the liquid phase. We use an all-coupling, finite-temperature variational method to study the formation of a ripplopolaron Wigner solid on a liquid helium film for different regimes of the electron-ripplon coupling strength. In addition to the three known phases of the ripplopolaron system (electron Wigner solid, polaron Wigner solid, and electron fluid), we define and identify a fourth distinct phase, the ripplopolaron liquid. We analyse the transitions between these four phases and calculate the corresponding phase diagrams. This reveals a reentrant melting of the electron solid as a function of temperature. The calculated regions of existence of the Wigner solid are in agreement with recent experimental data. 相似文献
13.
M. Sc. Hanna Pieper Dr. Serghei Chercheja Dr. Siegfried Eigler M. Sc. Christian E. Halbig Dr. Milos R. Filipovic Prof. Dr. Andriy Mokhir 《Angewandte Chemie (International ed. in English)》2016,55(1):405-407
Potential biomedicinal applications of graphene oxide (GO), for example, as a carrier of biomolecules or a reagent for photothermal therapy and biosensing, are limited by its cytotoxicity and mutagenicity. It is believed that these properties are at least partially caused by GO‐induced oxidative stress in cells. However, it is not known which chemical fragments of GO are responsible for this unfavorable effect. We generated four GOs containing variable redox‐active groups on the surface, including Mn2+, C‐centered radicals, and endoperoxides (EPs). A comparison of the abilities of these materials to generate reactive oxygen species in human cervical cancer cells revealed that EPs play a crucial role in GO‐induced oxidative stress. These data could be applied to the rational design of biocompatible nontoxic GOs for biomedical applications. 相似文献
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Marina Zveaghintseva Eugenia Stingaci Serghei Pogrebnoi Anastasia Smetanscaia Vladimir Valica Livia Uncu Victor Ch. Kravtsov Elena Melnic Anthi Petrou Jasmina Glamo
lija Marina Sokovi Alejandro Carazo Pemysl Mladnka Vladimir Poroikov Athina Geronikaki Fliur Z. Macaev 《Molecules (Basel, Switzerland)》2021,26(14)
Herein we report the synthesis of some new 1H-1,2,4-triazole functionalized chromenols (3a–3n) via tandem reactions of 1-(alkyl/aryl)-2-(1H-1,2,4-triazole-1-yl) with salicylic aldehydes and the evaluation of their antifungal activity. In silico prediction of biological activity with computer program PASS indicate that the compounds have a high novelty compared to the known antifungal agents. We did not find any close analog among the over 580,000 pharmaceutical agents in the Cortellis Drug Discovery Intelligence database at the similarity cutoff of 70%. The evaluation of antifungal activity in vitro revealed that the highest activity was exhibited by compound 3k, followed by 3n. Their MIC values for different fungi were 22.1–184.2 and 71.3–199.8 µM, respectively. Twelve from fourteen tested compounds were more active than the reference drugs ketoconazole and bifonazole. The most sensitive fungus appeared to be Trichoderma viride, while Aspergillus fumigatus was the most resistant one. It was found that the presence of the 2-(tert-butyl)-2H-chromen-2-ol substituent on the 4th position of the triazole ring is very beneficial for antifungal activity. Molecular docking studies on C. albicans sterol 14α-demethylase (CYP51) and DNA topoisomerase IV were used to predict the mechanism of antifungal activities. According to the docking results, the inhibition of CYP51 is a putative mechanism of antifungal activity of the novel chromenol derivatives. We also showed that most active compounds have a low cytotoxicity, which allows us to consider them promising antifungal agents for the subsequent testing activity in in vivo assays. 相似文献
16.
A. Serghei Y. Mikhailova K.-J. Eichhorn B. Voit F. Kremer 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):3006-3010
The dynamic glass transition and the dilatometric glass transition temperature are simultaneously characterized in thin films of hyperbranched aromatic polyesters by broadband dielectric spectroscopy and capacitive scanning dilatometry. A diverging thickness dependence is detected: while the temperature position of the alpha relaxation peak Tα decreases by ∼30 K, the dilatometric Tg increases by ∼10 K with decreasing film thickness. This emphasizes the subtle character of the glass transition phenomenon—as manifested in the molecular dynamics and in the (structural) thermal expansion—and proves that, in contrast to the bulk, different experimental techniques do not necessarily deliver similar results in confinement. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3006–3010, 2006 相似文献
17.
E.U. Mapesa M. Erber M. Tress K.-J. Eichhorn A. Serghei B. Voit F. Kremer 《The European physical journal. Special topics》2010,189(1):173-180
Broadband Dielectric Spectroscopy (BDS) and Ellipsometry are combined to study the glassy dynamics of nanometric layers (≥
5 nm) of polystyrene. For the former, two types of sample arrangement are applied, that is, the conventional method where
evaporated metal electrodes are used and a novel technique in which insulating silica nanostructures serve as spacers between
highly conducting doped silicon counter electrodes. Within the limits of the experimental accuracy (± 2 K) both approaches,
BDS and Ellipsometry, deliver the coinciding result that – compared to the bulk – the glassy dynamics is not shifted. Furthermore the dielectric measurements do not indicate any broadening of the relaxation time distribution function, independent of the sample geometry employed. 相似文献
18.
Electrical conductivity and translational diffusion in the 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid 总被引:1,自引:0,他引:1
Sangoro J Iacob C Serghei A Naumov S Galvosas P Kärger J Wespe C Bordusa F Stoppa A Hunger J Buchner R Kremer F 《The Journal of chemical physics》2008,128(21):214509
Broadband dielectric and terahertz spectroscopy (10(-2)-10(+12) Hz) are combined with pulsed field gradient nuclear magnetic resonance (PFG-NMR) to explore charge transport and translational diffusion in the 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The dielectric spectra are interpreted as superposition of high-frequency relaxation processes associated with dipolar librations and a conductivity contribution. The latter originates from hopping of charge carriers on a random spatially varying potential landscape and quantitatively fits the observed frequency and temperature dependence of the spectra. A further analysis delivers the hopping rate and enables one to deduce--using the Einstein-Smoluchowski equation--the translational diffusion coefficient of the charge carriers in quantitative agreement with PFG-NMR measurements. By that, the mobility is determined and separated from the charge carrier density; for the former, a Vogel-Fulcher-Tammann and for the latter, an Arrhenius temperature dependence is obtained. There is no indication of a mode arising from the reorientation of stable ion pairs. 相似文献
19.
Probing the effect of anion structure on the physical properties of cationic 1,2,3‐triazolium‐based poly(ionic liquid)s
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Mona M. Obadia Sébastien Fagour Yakov S. Vygodskii Frédéric Vidal Anatoli Serghei Alexander S. Shaplov Eric Drockenmuller 《Journal of polymer science. Part A, Polymer chemistry》2016,54(14):2191-2199
To extensively explore the influence of anion structure on the physical properties of poly(ionic liquid)s (PILs) a series of PILs having main‐chain 1,2,3‐triazolium cations was synthesized via copper(I)‐catalyzed azide‐alkyne 1,3‐dipolar cycloaddition (CuAAC) followed by N‐alkylation with iodomethane and anion metathesis with different metal salts, that is, Li(CF3SO2)2N, Li(CF3CF2SO2)2N, K(FSO2)2N, K(CF3SO2)N(CN), Ag(CN)2N, and sodium 4,5‐dicyano‐1,2,3‐triazolate. To isolate the effect of anion on physical properties of PILs, a common iodide precursor was used to maintain constant the average degree of polymerization (DPn) and chain dispersity. Detailed structure/properties relationship analyses demonstrated a lack of correlation between anion chemical structure, ionic conductivity, and glass transition temperatures. Among synthesized series, the PIL derivative having bis(trifluoromethylsulfonyl)imide counter anion showed the best compromise in performance: low glass transition temperature (Tg = ?68 °C), high thermal stability (Tonset = 340 °C) and superior ionic conductivity (σDC = 8.5 × 10? 6 S/cm at 30 °C), which makes it an interesting candidate for various key modern electrochemical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2191–2199 相似文献
20.
A convenient method for the synthesis of bicyclic 4-aminopyrimidines is described, involving the reaction of dinitriles with mononitriles in the presence of catalytic potassium tert-butoxide. These reactions proceed via the Thorpe-Ziegler cyclization of the dinitrile to form an intermediate β-cyanoenamine, which then undergoes annulation with the mononitrile in situ. 相似文献