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81.
Bagautdin Bagautdinov Zachery Shaw Andrii Orlov Marat A. Aliev 《Phase Transitions》2016,89(5):471-479
A rich sequence of structural modulations in Cs2HgCl4 as a function of temperature was studied by means of X-ray diffraction. Accurate satellite-position measurements on the cooling and heating paths of the crystal revealed abnormal thermal hystereses for incommensurate phases and coexistences of neighboring commensurate phases. A well-defined X-ray picture of the a-axis modulated phases in the range of 221–184 K were observed on the heating path, while the c-axis modulated phases existing below 184 K were definitely detected on the cooling path. The proper conditions for a precise phase diagram of Cs2HgCl4 can be correlated with relatively defect-free transformations of a-axis modulations at heating and of c-axis modulations at cooling. The peculiarity of Cs2HgCl4 to switch modulation direction among the a- and c-axes at 184 K allows us deliberately accumulate and thus control a majority of mobile defects on the mutually perpendicular (100) or (001) planes by possessing crystal within temperature domain of a- or c-axes modulations, respectively. 相似文献
82.
Importance of a Fluorine Substituent for the Preparation of meta‐ and para‐Pentafluoro‐λ6‐sulfanyl‐Substituted Pyridines
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Dr. Mikhail Kosobokov Benqiang Cui Dr. Andrii Balia Kohei Matsuzaki Etsuko Tokunaga Norimichi Saito Prof. Dr. Norio Shibata 《Angewandte Chemie (International ed. in English)》2016,55(36):10781-10785
Although there are ways to synthesize ortho‐pentafluoro‐λ6‐sulfanyl (SF5) pyridines, meta‐ and para‐SF5‐substituted pyridines are rare. We disclose herein a general route for their synthesis. The fundamental synthetic approach is the same as reported methods for ortho‐SF5‐substituted pyridines and SF5‐substituted arenes, that is, oxidative chlorotetrafluorination of the corresponding disulfides to give pyridylsulfur chlorotetrafluorides (SF4Cl‐pyridines), followed by chloride/fluoride exchange with fluorides. However, the trick in this case is the presence on the pyridine ring of at least one fluorine atom, which is essential for the successful transformation of the disulfides into m‐and p‐SF5‐pyridines. After enabling the synthesis of an SF5‐substituted pyridine, ortho‐F groups can be efficiently substituted by C, N, S, and O nucleophiles through an SNAr pathway. This methodology provides access to a variety of previously unavailable SF5‐substituted pyridine building blocks. 相似文献
83.
Rochelly da Silva Mesquita Andrii Kyrylchuk Anton Cherednichenko Ingrity Suelen Costa S Lílian Macedo Bastos Felipe Moura Araújo da Silva Rita de Cssia Saraiva Nunomura Andriy Grafov 《Molecules (Basel, Switzerland)》2022,27(10)
Alkaloids are natural products known as ethnobotanicals that have attracted increasing attention due to a wide range of their pharmacological properties. In this study, cholinesterase inhibitors were obtained from branches of Abuta panurensis Eichler (Menispermaceae), an endemic species from the Amazonian rainforest. Five alkaloids were isolated, and their structure was elucidated by a combination of 1D and 2D 1H and 13C NMR spectroscopy, HPLC-MS, and high-resolution MS: Lindoldhamine isomer m/z 569.2674 (1), stepharine m/z 298.1461 (2), palmatine m/z 352.1616 (3), 5-N-methylmaytenine m/z 420.2669 (4) and the N-trans-feruloyltyramine m/z 314.1404 (5). The compounds 1, 3, and 5 were isolated from A. panurensis for the first time. Interaction of the above-mentioned alkaloids with acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes was investigated in silico by molecular docking and molecular dynamics. The molecules under investigation were able to bind effectively with the active sites of the AChE and BChE enzymes. The compounds 1–4 demonstrated in vitro an inhibitory effect on acetylcholinesterase with IC50 values in the range of 19.55 µM to 61.24 µM. The data obtained in silico corroborate the results of AChE enzyme inhibition. 相似文献
84.
Prof. Dr. Alexander A. Ishchenko Prof. Dr. Nikolay O. Mchedlov-Petrossyan Dr. Nika N. Kriklya Dr. Aleksandr P. Kryshtal Prof. Dr. Eiji Ōsawa Andrii V. Kulinich 《Chemphyschem》2019,20(8):1028-1035
Among cationic, anionic, and merocyanine polymethine dyes, the binding to detonation nanodiamond (DND) colloid particles in hydrosol occurs only for negatively charged dye species. This, in view of the positive ζ-potential of the DND used in this study, suggests the predominance of electrostatic interactions over other intermolecular forces in such systems. Indeed, after decorating the merocyanine and the cationic dye by one and two negatively charged sulfopropyl groups, respectively, so that the net charge of their colored species becomes negative, the compounds also demonstrate affinity to the DND particles. In all cases, the binding of dyes to DND is accompanied by a decrease in fluorescence intensity and a bathochromic shift of their absorption and fluorescence bands. A quantitative study of the dyes adsorption on the DND nanoparticles as performed using the Küster-Freundlich and Langmuir equations reveals some peculiarities of their attaching to the DND aggregates and allows estimating the specific area of the DND particles at a concentration of 0.0212 wt/vol %. 相似文献
85.
Dr. Tetiana N. Starodub Dr. Erik Čižmár Andrii Kliuikov Prof. Vladimir A. Starodub Prof. Alexander Feher Dr. Mariana Kozlowska 《ChemistryOpen》2019,8(7):984-988
We report a new antiferromagnetic radical-anion salt (RAS) formed from 7,7,8,8-tetracyanquinonedimethane (TCNQ) anion and 2-amino-5-chloro-pyridine cation with the composition of (N−CH3−2-NH2−5Cl−Py)(TCNQ)(CH3CN). The crystallographic data indicates the formation of (TCNQ)2.− radical-anion π-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π-dimers characterize with strong π-stacking “pancake” interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ)2.− π-dimers bound in the endless chainlets via supramolecular bonds with (N−CH3−2-NH2−5-Cl−Py)+ cations, the repulsion forces are screened, allowing for specific parallel π-stacking interactions and stable radical-anion dimers formation. Measurements of magnetic susceptibility and magnetization confirm antiferromagnetic properties of RAS, what is in line with the higher stability of ground singlet state of the radical-anion pair, calculated by means of the DFT. Therefore, the reported radical-anion (N−CH3−2-NH2−5Cl−Py)(TCNQ)(CH3CN) solvate has promising applications in novel magnetics with supramolecular structures. 相似文献
86.
Anurag Noonikara-Poyil Alvaro Muoz-Castro Andrii Boretskyi Pavel K. Mykhailiuk H. V. Rasika Dias 《Chemical science》2021,12(43):14618
Polyfluorinated, electron-withdrawing, and sterically demanding supporting ligands are of significant value in chemistry. Here we report the assembly and use of a bis(pyrazolyl)borate, [Ph2B(3-(SF5)Pz)2]− that combines all such features, and involves underutilized pentafluorosulfanyl substituents. The ethylene and carbonyl chemistry of copper(i) supported by [Ph2B(3-(SF5)Pz)2]−, a comparison to the trifluoromethylated counterparts involving [Ph2B(3-(CF3)Pz)2]−, as well as copper catalyzed cyclopropanation of styrene with ethyl diazoacetate and CF3CHN2 are presented. The results from cyclopropanation show that SF5 groups dramatically improved the yields and stereoselectivity compared to the CF3.Copper–ethylene and carbonyl complexes of the newly developed [Ph2B(3-(SF5)Pz)2]− enable the study of ligand steric and electronic effects caused by the –SF5 group (dubbed “super CF3”), and a comparison to the –CF3 bearing analogs. 相似文献
87.
Liudmyla M. Grishchenko Galyna G. Tsapyuk Natalia S. Novichenko Oleksandr V. Mischanchuk Andrii V. Yatsymyrskiy Olga Yu. Boldyrieva 《Molecular Crystals and Liquid Crystals》2020,699(1):20-33
AbstractNanoporous activated carbon (NAC) beads that prepared by carbonization of microporous polymer 2,6-di-tert-butyl pyridine beads were subjected to bromination followed by amination to synthesize the NAC derivatives carrying amino groups. Grafted bromine groups, 0.41?mmol of Br per 1?g of NAC, are hydrolytic stable at 100 °С and can be successfully substituted by amino groups. SEM, TEM, and texture studies were shown a nanoporosity decrease. However, the aminated NAC beads maintained a narrow nanopore size distribution and high specific surface area, retaining a spherical shape. These beads were evaluated for capturing CO2 and showed good reversible adsorption capacity. The preparation method can easily be scaled up, and the NAC beads can be used for other adsorption applications where shaped carbon solids with developed nanoporosity are required. 相似文献
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Andrii V. Kulinich Nadezhda A. Derevyanko Alexander A. Ishchenko Stanislav L. Bondarev Valeri N. Knyukshto 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):106-113
The fluorescent properties of a series of symmetric cationic cyanine dyes and merocyanines with trimethylene bridge connecting N-atom of the indole residue with α-position of the polymethine chain have been explored in detail. It is shown that the constraining group influences their fluorescent properties both by steric and electronic effects. It revealed an essential decrease of the fluorescence quantum yields of the constrained symmetric cyanine dyes in comparison with those of their analogues without bridge group in their chromophore. This effect diminishes essentially at polymethine chain lengthening. In the case of merocyanines the bridge group can cause a decrease as well a substantial increase of their fluorescence quantum yields depending on their type of solvatochromism and solvent polarity. The conclusions made on the basis of the experimental data are in good agreement with the results of semiempirical quantum-chemical calculations. 相似文献