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61.
Kalevi Pihlaja Petri Thtinen Roustem Shaikhutdinov Heli Hartikainen Vladimir Ovcharenko Hikmet Agirbas Selahaddin Güner 《Journal of heterocyclic chemistry》2004,41(5):741-746
1,3‐Dipolar cycloaddition reactions of N‐methyl‐C‐arylnitrones with N‐phenyl‐ or N‐methylmaleimide were studied. The reaction of p‐dimethylamino‐, 4‐benzyloxy‐3‐methoxy‐, p‐nitro‐ and p‐chloro‐substituted phenylnitrones with N‐phenylmaleimide gave cis and trans cycloadducts but that of the corresponding phenylnitrones with N‐methylmaleimides only the cis adducts in the case of p‐dimethylamino and 4‐benzyloxy‐3‐methoxy substitution. All cis adducts attain a biased conformation whereas the trans forms are shown (by 1H NMR at 233 K and 13C NMR at 208 K) to be mixtures of two invertomers, namely o‐(N‐lone pair antiperiplanar to 3H; minor) and i‐conformations (3H‐C‐C‐3aH dihedral angle close to 90°; major). PM3 and DFT calculations at the B3LYP/6–31G(d) level of theory prove qualitatively that these two conformers of the trans adduct are of comparable stability and represent energy minima. 相似文献
62.
Freund Hans-Joachim Heyde Markus Kuhlenbeck Helmut Nilius Niklas Risse Thomas Schmidt Thomas Shaikhutdinov Shamil Sterrer Martin 《中国科学:化学(英文版)》2020,63(4):426-447
The review presents an overview of studies in the surface science of oxide and related surfaces with an emphasis of the studies performed in the authors' group. Novel instruments and technique developments, as well as their applications are reported, in an attempt to cover studies on model systems of increasing complexity, including some of the key ingredients of an industrially applied heterogeneous catalyst and its fabrication. The review is intended to demonstrate the power of model studies in understanding heterogeneous catalysis at the atomic level. The studies include those on supported nano-particles, both, prepared in vacuum and from solution, interaction of surfaces and the underlying bulk with molecules from the gas phase, strong metal support interaction, as well as the first attempt to include studies on reactions in confined spaces. 相似文献
63.
“Reduced” Coumarin Dyes with an O‐Phosphorylated 2,2‐Dimethyl‐4‐(hydroxymethyl)‐1,2,3,4‐tetrahydroquinoline Fragment: Synthesis,Spectra, and STED Microscopy
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Dr. Shamil Nizamov Dr. Maksim V. Sednev Prof. Mariano L. Bossi Elke Hebisch Dr. Holm Frauendorf Prof. Stephan E. Lehnart Dr. Vladimir N. Belov Prof. Stefan W. Hell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11631-11642
Large Stokes‐shift coumarin dyes with an O‐phosphorylated 4‐(hydroxymethyl)‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline fragment emitting in the blue, green, and red regions of the visible spectrum were synthesized. For this purpose, N‐substituted and O‐protected 1,2‐dihydro‐7‐hydroxy‐2,2,4‐trimethylquinoline was oxidized with SeO2 to the corresponding α,β‐unsaturated aldehyde and then reduced with NaBH4 in a “one‐pot” fashion to yield N‐substituted and 7‐O‐protected 4‐(hydroxymethyl)‐7‐hydroxy‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline as a common precursor to all the coumarin dyes reported here. The photophysical properties of the new dyes (“reduced coumarins”) and 1,2‐dihydroquinoline analogues (formal precursors) with a trisubstituted C=C bond were compared. The “reduced coumarins” were found to be more photoresistant and brighter than their 1,2‐dihydroquinoline counterparts. Free carboxylate analogues, as well as their antibody conjugates (obtained from N‐hydroxysuccinimidyl esters) were also prepared. All studied conjugates with secondary antibodies afforded high specificity and were suitable for fluorescence microscopy. The red‐emitting coumarin dye bearing a betaine fragment at the C‐3‐position showed excellent performance in stimulation emission depletion (STED) microscopy. 相似文献
64.
65.
M. I. Petrov D. A. Balaev K. A. Shaikhutdinov B. P. Khrustalev 《Physics of the Solid State》1997,39(11):1749-1750
The effect of thermally activated phase slippage (TAPS) on the resistive properties of Y3/4Lu1/4Ba2Cu3O7+O7 composites has been studied. The experimental temperature dependences of the electrical resistance are described in terms
of the TAPS mechanism using the temperature dependences of the tunnel-junction critical current.
Fiz. Tverd. Tela (St. Petersburg) 39, 1956–1957 (November 1997) 相似文献
66.
M. I. Petrov D. A. Balaev D. M. Gokhfel’d K. A. Shaikhutdinov K. S. Aleksandrov 《Physics of the Solid State》2002,44(7):1229-1234
The temperature evolution of the current-voltage (I-U) characteristic of a contact of the break-junction type with direct conduction is investigated on a polycrystalline HTSC of the Y-Ba-Cu-O system. The experimental I-U characteristics possessing a hysteresis are correctly described in the framework of the Kümmel-Nicolsky theory for an S-N-S contact (S stands for a superconductor; N, for a normal metal) in which the Andreev reflection of quasiparticles from the N-S interface is considered. It is shown that the shape of the I-U curve, as well as the existence of a hysteresis, is determined by the ratio of the number of “long” and “short” intergranular boundaries in the polycrystal under investigation. The coincidence of the calculated and experimental I-U curves made it possible to estimate the effective length of “natural” intergranular boundaries in polycrystalline HTSC materials. The estimate is obtained from the experimental temperature dependence of the critical current in the sample under investigation. 相似文献
67.
M. I. Petrov D. A. Balaev S. V. Ospishchev K. A. Shaikhutdinov B. P. Khrustalev K. S. Aleksandrov 《Physics of the Solid State》1997,39(3):362-368
Composites are prepared from a high-temperature superconductor with the 1-2-3 structure and the low-temperature oxide BaPb3/4Bi1/4O3 with various volume concentrations of the high-temperature and low-temperature superconductors. The temperature dependences
of the electrical resistivities and critical current densities of the composites are measured. It is shown experimentally
that these composites comprise a synthetically created network of Josephson weak links (with a specified degree of coupling).
Fiz. Tverd. Tela (St. Petersburg) 39, 418–424 (March 1997)
Deceased. 相似文献
68.
Kirill N. Zelenin Igor V. Lagoda Valeriy V. Alekseyev Jari Sinkkonen Kalevi Pihlaja Roustem A. Shaikhutdinov 《Journal of heterocyclic chemistry》2002,39(4):805-810
A universal scheme is proposed for the molecular design of heterocyclic recyclizations by replacing the exocyclic hydroxyl groups in exo‐trig‐ ring‐chain tautomeric molecules with substituted amines or hydrazines. The practical applicability of this approach is demonstrated by the condensations of 5‐hydroxy‐5‐methyl‐3‐isoxazolidinones with thioaroyl‐hydrazines and 2‐aminomethylaniline. The condensation products were studied by modern 1H, 13C and 15N NMR spectroscopic methods using three solvents: CDC13, DMSO[D6] and CD3CN. The solvent was found to have a strong effect to the relative amounts of the tautomers. 相似文献
69.
Kozlov AV Semenov VE Mikhailov AS Aganov AV Smith MB Reznik VS Latypov SK 《The journal of physical chemistry. B》2008,112(10):3259-3267
Protonation (alkylation) sites of several thiopyrimidine derivatives were directly determined by 1H-15N (1H-13C) heteronuclear single quantum coherence/heteronuclear multiple bond correlation methods, and it was found that in all compounds, protonation (methylation) occurred at the N1 nitrogen. GIAO DFT chemical shifts were in full agreement with the determined tautomeric structures. According to ab initio calculations, the stability of the different protonated forms and methylated derivatives was favored due to thermodynamic control and not kinetic control. 相似文献
70.
A. B. Glazyrin M. I. Abdullin N. A. Kochkov R. V. Karmanov S. T. Burtan N. V. Shaikhutdinov 《Russian Journal of Applied Chemistry》2008,81(9):1634-1637
Properties of polymer-asphalt compounds containing 1,2-polybutadienes differing in the molecular weight and structure of macromolecules were examined. Introduction of syndiotactic 1,2-polybutadiene in combination with a plasticizing additive noticeably improves the main service properties of asphalts. 相似文献