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21.
22.
Voinov MA Polienko JF Schanding T Bobko AA Khramtsov VV Gatilov YV Rybalova TV Smirnov AI Grigor'ev IA 《The Journal of organic chemistry》2005,70(24):9702-9711
[reaction: see text] An approach to the synthesis of new imidazoline nitroxides bearing an N',N'-disubstituted amidine group is reported. The approach is based on the alkylation of diamagnetic 4-R-amino-1,2,2,5,5-pentamethyl-3-imidazolines with bromoacetic acid ethyl ester; the products of alkylation are further oxidized to the corresponding nitroxides. The approach allows a variety of functional groups to be introduced into the nitroxide molecule structure. Alkylation with bromoacetic acid ethyl ester was found to proceed with high regioselectivity and afford the products of exo-alkylation. The regiochemical assignment is made on the basis of 13C NMR spectra and confirmed by X-ray diffraction study. All of the nitroxides synthesized here were shown to have pH-dependent EPR spectra with pKa ranging from 3.5 to 6.2. For nitroxides 13 bearing the carboxylic group remote to the nitroxide moiety, the changes in isotropic magnetic parameters of EPR spectra due to reversible deprotonation of the carboxylic group were found to be small. For these nitroxides, we demonstrate an alternative approach for pKa determination that is based on measuring the peak-to-peak line width of the EPR spectrum in the presence of the paramagnetic broadening agent potassium ferricyanide. The partition coefficients of nitroxides in octanol/H2O and octanol/phosphate buffer solution mixtures were measured to reveal a range of their lipophilicities. 相似文献
23.
Peter Schwendt Michal Sivák Andrey E. Lapshin Yury I. Smolin Yury F. Shepelev Dalma Gyepesov 《Transition Metal Chemistry》1994,19(1):34-36
Summary The monoperoxo complexes, M2[VO(HEDTA)(O2)]· 4H2O, where M is K+ or NH
4
+
and H4EDTA is ethylene-diaminetetraacetic acid, were prepared and characterized by Raman and i.r. spectra in the solid state and in aqueous solution. The single crystal X-ray study revealed a pentagonal bipyramidal anion structure with a tetradentate HEDTA(3—) ligand. The decomposition of complexes in aqueous solution to blue vanadium(IV) complexes as end products proceeds via a nonperoxo complex of vanadium. 相似文献
24.
For the five-coordinated complexes of ferroprotoporphynynn with imidazole, a quantum-chemical analysis of the electronic structure and Mossbauer spectral parameters has been canied out. Peripheral substituents (CH3, Cf13, C2H4COOH) were introduced into the porphynin macrocycle to model the real chemical structure of protopo'phynynn in the heme group of desoxyhemoglobin. The calculations have shown that near the occupation border in the complaes there are MO which are due to the -systems of the CH= CM2 and CH2CH2COOH substituents. The orientalion of the vinyl fragments has a considerable effect on the populations of the Fe d-orbitals and the quadrupole splitting EQ for the5B1 and5B2 terns.Institute of Biophysics, Ministry of Health, Russian Federation. Translated fromZhurnal Strukturmoi Khimii, Vol. 34, No. 5, pp. 90–93, September–October, 1993.Translated by L. Smolina 相似文献
25.
26.
Tsirelson Vladimir Abramov Yury Zavodnik Valery Stash Adam Belokoneva Elena Stahn Jochen Pietsch Ullrich Feil Dirk 《Structural chemistry》1998,9(4):249-254
The critical points in the model electron density distributions of LiF, NaF, NaCl, and MgO crystals, constructed from accurate X-ray diffraction data, are determined. For LiF and MgO they are compared with those obtained from a Hartree–Fock electron density calculation. Both experiment and theory show the same type of critical points on the bond lines. The topological features in areas between structural units, where the electron density is low and near-uniform, turn out to be model dependent and cannot be established well with the data available. Topological analysis of procrystals (hypothetical systems consisting of spherical atoms or ions placed on the same sites as atoms in real crystal) show that (3, –1) critical points, usually connected with bonding interaction, are observed on interatomic lines in these nonbonded systems as well. 相似文献
27.
28.
Yury L. Karavaev Alexander A. Kilin Anton V. Klekovkin 《Regular and Chaotic Dynamics》2016,21(7-8):918-926
In this paper we describe the results of experimental investigations of the motion of a screwless underwater robot controlled by rotating internal rotors. We present the results of comparison of the trajectories obtained with the results of numerical simulation using the model of an ideal fluid. 相似文献
29.
30.
V. P. Budaev S. A. Grashin A. V. Karpov S. V. Kraevskii L. N. Khimchenko 《JETP Letters》2012,95(2):78-84
Hierarchically granulated films formed on a material subjected to the action of a high-temperature plasma have been microscopically
studied. The statistical self-similarity of the structure of the surface from nanoscale to macroscale, as well as long-range
correlations in the relief that are due to the statistically inhomogeneous structure of granularity, has been revealed. 相似文献