排序方式: 共有197条查询结果,搜索用时 187 毫秒
61.
Dorozhkin EI Ignat'eva DV Tamm NB Goryunkov AA Khavrel PA Ioffe IN Popov AA Kuvychko IV Streletskiy AV Markov VY Spandl J Strauss SH Boltalina OV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(14):3876-3889
Reaction of C70 with ten equivalents of silver(I) trifluoroacetate at 320-340 degrees C followed by fractional sublimation at 420-540 degrees C and HPLC processing led to the isolation of a single abundant isomer of C70(CF3)n for n = 2, 4, 6, and 10, and two abundant isomers of C70(CF3)8. These six compounds were characterized by using matrix-assisted laser desorption ionization (MALDI) mass spectrometry, 2D-COSY and/or 1D 19F NMR spectroscopy, and quantum-chemical calculations at the density functional theory (DFT) level. Some were also characterized by Raman spectroscopy. The addition patterns for the isolated compounds were unambiguously found to be C1-7,24-C70(CF3)2, C1-7,24,44,47-C70(CF3)4, C2-1,4,11,19,31,41-C70(CF3)6, Cs-1,4,11,19,31,41,51,64-C70(CF3)8, C2-1,4,11,19,31,41,51,60-C70(CF3)8, and C1-1,4,10,19,25,41,49,60,66,69-C70(CF3)10 (IUPAC numbering). Except for the last compound, which is identical to the recently reported, crystallographically characterized C70(CF3)10 derivative prepared by a different synthetic route, these compounds have not previously been shown to have the indicated addition patterns. The largest relative yield under an optimized set of reaction conditions was for the Cs isomer of C70(CF3)8 (ca. 30 mol % of the sublimed mixture of products based on HPLC integration). The results demonstrate that thermally stable C70(CF3)n isomers tend to have their CF3 groups arranged on isolated para-C6(CF3)2 hexagons and/or on a ribbon of edge-sharing meta- and/or para-C6(CF3)2 hexagons. For Cs- and C2-C70(CF3)8 and for C2-C70(CF3)6, the ribbons straddle the C70 equatorial belt; for C1-C70(CF3)4, the para-meta-para ribbon includes three polar hexagons; for C1-7,24-C70(CF3)2, the para-C6(CF3)2 hexagon includes one of the carbon atoms on a C70 polar pentagon. The 10.3-16.2 Hz 7JF,F NMR coupling constants for the end-of-ribbon CF3 groups, which are always para to their nearest-neighbor CF3 group, are consistent with through-space Fermi-contact interactions between the fluorine atoms of proximate, rapidly rotating CF3 groups. 相似文献
62.
Vitaliy V. Khutoryanskiy Zauresh S. Nurkeeva Aibek D. Sergaziyev Janusz M. Rosiak 《European Polymer Journal》2003,39(4):761-766
The complex formation of poly-2-[(methacryloyloxy)-ethyl]trimethylammonium chloride (PMADQUAT) with poly(acrylic acid) (PAA) of different molecular weights has been studied in aqueous solutions by potentiometric, viscometric, turbidimetric and FTIR spectroscopic methods. The formation of insoluble non-stoichiometric polyelectrolyte complexes has been shown. The stability of polyelectrolyte complexes in solutions of different pH and ionic strength has been evaluated. The formation of polyelectrolyte complexes between hydrogels of PMADQUAT and linear PAA of different molecular weights has been studied. It was shown that the molecular weight of PAA considerably affects the kinetics of interaction as well as the final state of gel-polymer complex. 相似文献
63.
Victoria A. Ivolgina Margarita S. Chernov’yants Leonid D. Popov Vitaliy V. Suslonov Natalya A. Avtushenko Nikolay V. Luanguzov 《Phosphorus, sulfur, and silicon and the related elements》2020,195(5):421-428
AbstractAs a part of investigation of thyreostatic activity of mercapto-substituted triazoles, the structure, spectroscopic properties of 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione were obtained. 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione forms steady charge-transfer complex in dilute chloroform solution, coordinating one iodine molecule (lgβ?=?3.47). The reaction product of 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione is presented by uncharged adduct: C6H6N4OS·I2. The crystal structure of the adduct was studied in detail by single crystal X-ray diffraction. The results of thermogravimetric analysis revealed the stability of adduct in a solid state at the temperature range 50–500?°C. 相似文献
64.
Dothager RS Putt KS Allen BJ Leslie BJ Nesterenko V Hergenrother PJ 《Journal of the American Chemical Society》2005,127(24):8686-8696
Late-stage malignant melanoma is a cancer that is refractory to current chemotherapeutic treatments. The average survival time for patients with such a diagnosis is 6 months. In general, the vast majority of anticancer drugs operate through induction of cell cycle arrest and cell death in either the DNA synthesis (S) or mitosis (M) phase of the cell cycle. Unfortunately, the same mechanisms that melanocytes possess to protect cells from DNA damage often confer resistance to drugs that derive their toxicity from S or M phase arrest. Described herein is the synthesis of a combinatorial library of potential proapoptotic agents and the subsequent identification of a class of small molecules (triphenylmethylamides, TPMAs) that arrest the growth of melanoma cells in the G1 phase of the cell cycle. Several of these TPMAs are quite potent inducers of apoptotic death in melanoma cell lines (IC(50) approximately 0.5 muM), and importantly, some TPMAs are comparatively nontoxic to normal cells isolated from the bone marrow of healthy donors. Furthermore, the TPMAs were found to dramatically reduce the level of active nuclear factor kappa-B (NFkappaB) in the cell; NFkappaB is known to be constitutively active in melanoma, and this activity is critical for the proliferation of melanoma cells and their evasion of apoptosis. Compounds that reduce the level of NFkappaB and arrest cells in the G1 phase of the cell cycle can provide insights into the biology of melanoma and may be effective antimelanoma agents. 相似文献
65.
Grigoriy A. Mun Zauresh S. Nurkeeva Vitaliy V. Khutoryanskiy Aibek D. Sergaziyev 《Colloid and polymer science》2002,280(3):282-289
The complex formation reactions of poly(vinyl ether of diethylene glycol) as well as vinyl ether of diethylene glycol–vinyl
butyl ether copolymers with poly(acrylic acid) have been studied in aqueous and alcohol solutions. The formation of interpolymer
complexes which were stabilized by hydrogen bonds was shown. The effects of molecular weight of poly(acrylic acid) and the
nature of the nonionic polymer on the composition and stability of interpolymer complexes were clarified. The critical pH
values of complexation were determined for different systems with various molecular weights and hydrophobic–hydrophilic balances.
The stability of the interpolymer complexes formed in aqueous and alcohol solutions with respect to dimethylformamide addition
was evaluated. The role of hydrophobic interactions and the presence of active groups on stability of the interpolymer complexes
is discussed.
Received: 23 July 2001 Accepted: 27 September 2001 相似文献
66.
Aikaterini Vriza Angelos B. Canaj Rebecca Vismara Laurence J. Kershaw Cook Troy D. Manning Michael W. Gaultois Peter A. Wood Vitaliy Kurlin Neil Berry Matthew S. Dyer Matthew J. Rosseinsky 《Chemical science》2021,12(5):1702
The implementation of machine learning models has brought major changes in the decision-making process for materials design. One matter of concern for the data-driven approaches is the lack of negative data from unsuccessful synthetic attempts, which might generate inherently imbalanced datasets. We propose the application of the one-class classification methodology as an effective tool for tackling these limitations on the materials design problems. This is a concept of learning based only on a well-defined class without counter examples. An extensive study on the different one-class classification algorithms is performed until the most appropriate workflow is identified for guiding the discovery of emerging materials belonging to a relatively small class, that being the weakly bound polyaromatic hydrocarbon co-crystals. The two-step approach presented in this study first trains the model using all the known molecular combinations that form this class of co-crystals extracted from the Cambridge Structural Database (1722 molecular combinations), followed by scoring possible yet unknown pairs from the ZINC15 database (21 736 possible molecular combinations). Focusing on the highest-ranking pairs predicted to have higher probability of forming co-crystals, materials discovery can be accelerated by reducing the vast molecular space and directing the synthetic efforts of chemists. Further on, using interpretability techniques a more detailed understanding of the molecular properties causing co-crystallization is sought after. The applicability of the current methodology is demonstrated with the discovery of two novel co-crystals, namely pyrene-6H-benzo[c]chromen-6-one (1) and pyrene-9,10-dicyanoanthracene (2).Machine learning using one class classification on a database of existing co-crystals enables the identification of co-formers which are likely to form stable co-crystals, resulting in the synthesis of two co-crystals of polyaromatic hydrocarbons. 相似文献
67.
Vitaliy E. Diyuk Anna V. Vakaliuk Liudmyla M. Grishchenko Oleksandr V. Mischanchuk Dmytro V. Brazhnyk Vladyslav V. Lisnyak 《Molecular Crystals and Liquid Crystals》2020,699(1):9-19
AbstractMulti-walled carbon nanotubes (MWCNTs) have an ordered geometric structure, large specific surface area, prominent electrical conductivity, and unique mechanical properties. They are nontoxic and can be used in biomedicine. Physical and surface chemical characteristics of MWCNTs should be tuned to that required to improve certain properties and obtain a variety of functional materials. We modified the MWNTs by using the barothermal Diels-Alder reaction with dienophiles, p-benzoquinone, fumaronitrile, and maleimide, to address this issue. The prepared MWCNTs were studied by SEM-EDX, nitrogen adsorption porometry, ATR FTIR, and thermal analysis. Results showed that both separate and conjugated C?=?C bonds at the edge and outer/inner surface of walls could react with dienophiles. The grafted groups are separated by the temperature on weak (low-temperature) and strong (high-temperature) chemisorbed forms; they are detached at temperatures below and above 350?°C, correspondingly. Thermal analysis shows that up to 5% of the carbon atoms are involved in the [4?+?2] cycloaddition. The high-temperature forms of the grafted groups under extreme heating can be involved in the retro-Diels-Alder reaction that breaks six-membered rings, producing a dienophile. 相似文献
68.
Vitaliy Smokal Oksana Kharchenko Yuriy Karabets Andrii Kysil Oksana Krupka 《Molecular Crystals and Liquid Crystals》2018,672(1):11-17
ABSTRACTIn this work we report preliminary results obtained for methacrylic polymers incorporating aurone side-group as photochemical active molecule. The aurone polymers were obtained by a three-step synthetic approach: (2Z)-6-hydroxy-2-(4-R-benzyliden)-1-benzofuran-3(2H)-ones were synthesized by using condensation reation of 6-hydroxybenzofuran-3-one with benzaldehydes; then methacrylate monomers were synthesized by reaction the alcohols with methacryloyl chloride; and the polymers were synthesized by free radical polymerization. Polymers were characterized by 1HNMR spectroscopy and DSC techniques. Their physicochemical properties are determined by absorption, fluorescence excitation and emission spectroscopies. 相似文献
69.
Grigoriy A. Mun Zauresh S. Nurkeeva Vitaliy V. Khutoryanskiy Galiya S. Azhgozhinova Erengaip M. Shaikhutdinov Kinam Park 《Macromolecular rapid communications》2002,23(16):965-967
Complex formation of poly(methacrylic acid) hydrogels with linear poly(ethylene glycol) has been studied at different pH values and in the presence of an electric field. The fastest contraction of the gel samples was observed under simultaneous action of electric field and complex formation.
70.
Victor I. Sokolov Sergey F. Dubinin Vitaliy D. Parkhomenko Vladimir V. Gudkov Alexander V. Tkach Nikita B. Gruzdev 《Solid State Communications》2004,129(8):507-510
Neutron diffraction and ultrasonic experiments as well as measurements of heat conductivity in ZnSe and Zn1−xNixSe (x=0.0025) semiconductors have been carried out. As a result, a structural transition induced by Ni impurity has been found at 相似文献