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61.
Igor L. Dalinger Irina A. Vatsadze Tatyana K. Shkineva Galina P. Popova Svyatoslav A. Shevelev Yuliya V. Nelyubina 《Journal of heterocyclic chemistry》2013,50(4):911-924
3,4,5‐Trinitro‐1H‐pyrazole ( 1 ) has been obtained via nitration of 3,5‐dinitropyrazole with mixture of sulfuric and nitric acids. Compound 1 reacts with excess ammonia and aliphatic amines, in the presence of bases with NH‐azoles, phenols, thiols, and triflouroethanol at mild conditions in water. All these reactions occur as the nucleophilic substitution of the nitro‐group at position 4 in 1 affording 4‐R‐3,5‐dinitropyrazoles. The product of methylation of 1 , N‐methyl‐3,4,5‐trinitropyrazole ( 4 ), also reacts with thiols, phenols, oximes, ammonia, amines, and NH‐azoles. The reactions proceed with high yields but nucleophilic substitutions in these cases occur regioselectively at position 5 in 4 to afford 5‐R‐3,4‐dinitropyrazoles. 相似文献
62.
Eugene V. Tretyakov Svyatoslav E. TolstikovElena V. Gorelik Matvey V. FedinGalina V. Romanenko Artem S. BogomyakovVictor I. Ovcharenko 《Polyhedron》2008
It was established that the reactions of pyrazol-3-yl-substituted nitronyl nitroxide (HL1) and pyrazol-3-yl-substituted imino nitroxide (HL3) with Cu(II) acetate lead to self-assembly of the Cu4(OH)2(OAc)4(DMF)2(L1)2 tetranuclear and Cu2(OAc)2(H2O)2(L3)2 dinuclear complexes, respectively. The reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted nitronyl nitroxide (HL2) gave unexpected solid Cu2(H2O)2(L6)2 · 2DMF, in which L6 is a deprotonated 5-carboxy-pyrazol-3-yl-substituted nitronyl nitroxide, formed as a result of cleavage of an ester bond in the starting HL2. A similar transformation of the paramagnetic ligand was observed in the reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted imino nitroxide (HL4). It led to the formation of Cu2(DMF)2(L7)2, where L7 is deprotonated 2-(5-carboxy-1H-pyrazol-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide. An X-ray diffraction study indicated that in Cu4(OH)2(OAc)4(DMF)2(L1)2 and Cu2(OAc)2(H2O)2(L3)2, the L1 and L3 paramagnetic ligands perform the bridging cyclic tridentate function, while in Cu2(H2O)2(L6)2 · 2DMF and Cu2(DMF)2(L7)2, the paramagnetic L6 and diamagnetic L7 are bridging bicyclic tetradentate ligands. The magnetic behavior of complexes with coordinated nitronyl nitroxide – Cu4(OH)2(OAc)4(DMF)2(L1)2 and Cu2(H2O)2(L6)2 · 2DMF is dictated by the dominant antiferromagnetic exchange interactions, which is confirmed by quantum-chemical data. The magnetic susceptibility of Cu2(OAc)2(H2O)2(L3)2 reflects the competition between the antiferromagnetic and ferromagnetic components, of which the latter is due to electron coupling in the Cu(II) ← N=C–N ? O exchange channels. EPR data confirm the results received from static magnetic measurements for multispin solids. 相似文献
63.
S. V. Trukhanov A. V. Trukhanov A. N. Vasil’ev A. Maignan H. Szymczak 《JETP Letters》2007,85(10):507-512
For La 0.825 3+ Sr 0.175 2 +Mn3+O 2.912 2? anion-deficient manganite, the specific magnetization, the dynamic magnetic susceptibility, and the heat capacity are investigated. This material is found to be an inhomogeneous ferromagnet below the Curie point T C ≈ 122 K, which is much lower than the Curie point determined for the stoichiometric composition (T C ≈ 268 K). An increase in magnetic field by two orders of magnitude leads to an increase in the Curie temperature by ΔT ≈ 12 K. The presence of oxygen vacancies leads to the frustration of a part, namely, V fr ≈ 22%, of the indirect Mn3+-O-Mn3+ exchange interactions, but the spin glass state is not realized. The ferromagnetic matrix of the material under study is characterized by a scatter in the exchange interaction intensities. The heat capacity is found to exhibit an anomalous behavior. Based on the Banerjee magnetic criterion, it is established that the ferromagnet-paramagnet transition observed for La 0.825 3+ Sr 0.175 2+ Mn3+O 2.912 2? anion-deficient manganite is a second-order thermodynamic phase transition. The mechanism and origin of the critical behavior of the system under investigation are discussed. 相似文献
64.
Maxim R. Ryzhikov Vladimir A. Slepkov Svetlana G. Kozlova Svyatoslav P. Gabuda Vladimir E. Fedorov 《Journal of computational chemistry》2015,36(28):2131-2134
Monolayers of molybdenum disulfide MoS2 are considered to be prospective materials for nanoelectronics and various catalytic processes. Since in certain conditions they undergo 1T ? 2H phase transitions, studying these phase changes is an urgent task. We present a DFT research of these transitions to show that they can proceed as a solid‐state reaction. Two transition states were discovered with energy barriers 1.03 and 1.40 eV. Sulfur atoms in the transition states are shown to be displaced relative to molybdenum atoms so that a tendency of one structural modification to transform into the other modification is seen. This kind of displacements agrees with electron microscopy data reported earlier. The energy parameters indicate that 1T → 2H reactions are exothermic for both transition states and can possibly proceed in a self‐sustained manner when initially activated by some external energy impact. © 2015 Wiley Periodicals, Inc. 相似文献
65.
Alex Trukhanov Larisa Panina Sergei Trukhanov Vitalii Turchenko Mohamed Salem 《中国物理 B》2016,25(1):16102-016102
The investigations of the crystal and magnetic structures of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been performed with powder neutron diffractometry. Magnetic properties of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been measured by vibration sample magnetometry at different temperatures under different magnetic fields.The atomic coordinates and lattice parameters have been Rietveld refined. The invar effect is observed in low temperature range(from 4.2 K to 150 K). It is explained by the thermal oscillation anharmonicity of atoms. The increase of microstress with decreasing temperature is found from Rietveld refinement. The Curie temperature and the change of total magnetic moment per formula unit are found for all compositions of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed. 相似文献
66.
S.V. Trukhanov D.P. Kozlenko A.V. Trukhanov 《Journal of magnetism and magnetic materials》2008,320(14):e88-e91
The magnetic state of La0.70Sr0.30MnOx (x=2.85, 2.80) anion-deficient manganites is studied experimentally under hydrostatic pressure up to 5.2 GPa. These materials possessing the properties of a spin-glass state. The La0.70Sr0.30MnO2.85 exhibits a coexistence of the rhombohedral (R3¯c) and tetragonal (I4/mcm) crystal structures and below Tf 50 K the spin-glass state is formed. The La0.70Sr0.30MnO2.80 exhibits the tetragonal (I4/mcm) crystal structure. For this compound a phase-separated magnetic state below Tf is formed, involving coexistence of C-type antiferromagnetic (AFM) clusters within spin-glass matrix. In both compounds the crystal structure and magnetic states remain stable upon compression. Under the hydrostatic pressure up to 1 GPa, the La0.70Sr0.30MnO2.85 is a spin glass with a smeared phase transition to the paramagnetic state. The freezing temperature Tf of the magnetic moments of the ferromagnetic clusters increases at a rate of 4.30 K/GPa and the magnetic ordering temperature TMO increases at a rate of 12.90 K/GPa. The enhancement of the ferromagnetic properties of La0.70Sr0.30MnO2.85 anion-deficient manganite under hydrostatic pressure is explained by the redistribution of oxygen vacancies and a decrease in the unit cell parameters. 相似文献
67.
E. M. Trukhanov A. P. Vasilenko I. D. Loshkarev A. V. Kolesnikov 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(4):307-310
Misfit stress relaxation processes in a semiconductor heterosystem are divided into optimal and nonoptimal. Depending on the type of a process and degree of its completeness, four variants of a uniform stress field are established and experimentally detected in the surface layer of an epitaxial film. The interaction between threading dislocations that favors the transformation of nonoptimal relaxation into optimal is investigated. 相似文献
68.
S.V Trukhanov N.V Kasper I.O TroyanchukM Tovar H SzymczakK Bärner 《Journal of solid state chemistry》2002,169(1):85-95
The crystal structure, magnetic and electrical properties of the La1−xCaxMnO3−γ (x=0.30, 0.50; 0?γ?0.50) oxygen-deficient manganites have been studied. It is found that the compounds La0.70Ca0.30MnO3−γ possess a long-range ferromagnetic order up to γ=0.06 and a cluster spin glass behavior at 0.06<γ?0.20. Antiferromagnetic state of La0.50Ca0.50MnO3−γ (γ=0) composition transforms into inhomogeneous ferromagnetic one at γ=0.04. The system converts into cluster spin glass state at γ=0.10. As oxygen deficit reaches the value γ=0.25, a new type of ferromagnetic phase appears. The fraction of this ferromagnetic phase is the highest in the composition γ=0.30. It is supposed that the compounds with γ?0.35 represent an antiferromagnetic medium with inclusions of the ferromagnetic phase. The strongly reduced samples exhibit a large magnetoresistance below the temperature, at which the spontaneous magnetization develops. The magnetic phase diagrams of both La0.70Ca0.30MnO3−γ and La0.50Ca0.50MnO3−γ systems have been constructed. We argue, that the oxygen vacancies are disordered in the La0.70Ca0.30MnO3−γ system in the studied region of oxygen vacancies concentration (0?γ<0.20) whereas for the La0.50Ca0.50MnO3−γ they tend to order at γ>0.25 in a manner of Sr2Fe2O5-type crystal structure. This study shows that Mn3+-O-Mn3+ ferromagnetic interaction may play an important role in the formation of magnetic state of manganites. 相似文献
69.
P. N. Baronets A. F. Kolesnikov S. N. Kubarev I. S. Pershin A. S. Trukhanov M. I. Yakushin 《Fluid Dynamics》1991,26(3):437-442
The results of measuring and numerically calculating the surface temperature distributions of heat-shield tiles with uniform and nonuniform catalytic coatings exposed to subsonic dissociated-air flows in an induction plasmotron are presented. The measurements are consistent with the calculated surface temperature profiles obtained from a numerical solution of the Navier-Stokes equations for a chemical-nonequilibrium flow of dissociated nitrogen. The results are compared with the data of a space shuttle flight experiment on the effect of a discontinuity of heat shield catalyticity on the overequilibrium surface temperature jump.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 144–150, May–June, 1991. 相似文献
70.
V. M. Lebedev N. G. Platova A. V. Spassky K. A. Trukhanov 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(3):343-346
The impact of ionizing radiation and hypomagnetic conditions on seeds of the lettuce Lactuca sativa L. is studied on the 120-cm cyclotron at the Skobeltsyn Institute of Nuclear Physics. The seeds are irradiated with α-particles with energies of around 25.8 MeV and placed to germinate in a hypomagnetic chamber under conditions of an attenuated (up to 2500 times) geomagnetic field. Chromosomal aberrations in the first mitosis of the root meristem are analyzed. Changes in the irradiated samples are observed when compared to control samples. Hypomagnetic conditions greatly magnify the negative impact of ionizing radiation. 相似文献