O. Ya. Grinberg
Russian Academy of Sciences
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Chemical Physics Letters | 1994
S. D. Chemerisov; O. Ya. Grinberg; D. S. Tipikin; Ya. S. Lebedev; H. Kurreck; K. Möbius
The mechanochemical activation of polycrystalline mixtures of porphyrins and quinones (as well as some other donors and quinones) was found to produce large concentrations of triplet radical pairs with unusual stability in the solid state matrix. High-field/high-frequency (2 mm band) EPR experiments allowed observation of low-temperature spin polarization and determination of the sign of the zero-field splitting parameters D. They appeared to be positive, in contrast to most in chemically or photochemically produced donor—acceptor radical pairs, for which the point dipole approximation (D<0) holds. To explain the experimental results, a matrix stabilization mechanism of exciplexes in the course of mechanochemically initiated electron (or hydrogen) transfer is postulated.
Archive | 1992
Ya. S. Lebedev; O. Ya. Grinberg; A. A. Dubinsky; Oleg G. Poluektov
The enhanced effectivity of spin-label and probe techniques is discussed. The 2-mm wavelength band is suggested for detecting EPR in high fields. The general principles of construction of 2-mm band EPR spectrometers are described and the physical background of resolution improvement in high fields is discussed. Experimental results from the determination of a full set of magnetic resonance parameters of nitroxyl radicals and biradicals in various media are reported. It is shown that these data allow adequate selection of spin labels and probes for biological species. The experimental evidence for molecular motions of spin labels in synthetic and biological objects is reported. The 2-mm band EPR permits one to obtain unique information on the anisotropy of label rotation and select molecular reorientation models. The technique also extends the range of the correlation times under investigation. Orientational ordering is studied for some samples. Thus, although the experimental setups required for 2-mm band studies at high magnetic fields (up to 50 kG) is quite complicated, the technique has important advantages as it is very informative and extends the range of applications of the EPR method for investigating paramagnetic models.
Applied Magnetic Resonance | 1993
V. E. Galtsev; O. Ya. Grinberg; Ya. S. Lebedev; E. V. Galtseva
The four-fold improvement of EPR signal-to-noise ratio for radiation-induced paramagnetic centres in comparison with a conventional way is achieved by detection of the tooth enamel EPR signal at 77 K and rapid passage conditions.
Russian Chemical Bulletin | 1985
V.I. Krinichnyi; O. Ya. Grinberg; I. B. Nazarova; G. I. Kozub; L. I. Tkachenko; M. L. Khidekel; Ya. S. Lebedev
Conclusions1.A dependence of the magnetic resonance parameters on the nature of the anion was established for organic polythiophene conductors with various anions.2.The major values of the anisotropic g-tensor were measured by 2-mm band ESR spectroscopy and the conductivity of polythiophene (BF4− and polyacetylene (I−) was evaluated at 200°K.
Journal of Radioanalytical and Nuclear Chemistry | 1994
V. E. Galtsev; E. V. Galtseva; O. Ya. Grinberg; Ya. S. Lebedev
Rapid Passage Effects were used to suppress the background signal, thus enabling low γ-radiation accumulated dose determination. Together with optimal temperature and detection conditions, the suggested approach proved to provide EPR dosimetry in the most actual dose range between 10 and 200 rad.
Theoretical and Experimental Chemistry | 1990
O. G. Poluktov; O. Ya. Grinberg; A. A. Dubinskii; O. Yu. Sidorov; Ya. S. Lebedev
A study is presented on models for the motion of spin-label macromolecules indicated by 3 cm and 2 mm ESR spectra. Theoretical calculations are employed to simulate combination of the relative motion with transport motion (in conjunction with a macromolecule segment) for various temperature-viscosity relationships in the anisotropic Brownian diffusion of nitroxyl radicals. In that approach, one cannot match the relaxation effects in the two sets of spectra. It is concluded that there are fast relative label oscillations that do not average the g and A tensors to axisymmetric ones.
Chemical Physics Letters | 1975
V.I. Barchuk; A. A. Dubinsky; O. Ya. Grinberg; Ya. S. Lebedev
Abstract UV irradiation of benzoyl peroxide single crystals produced radical pairs (PhCO 2 …Ph) in four magnetically different positions. With linearly polarised light the photoselection effect was observed which was used to study the nature of the primary photoexcitation.
Russian Chemical Bulletin | 1979
Yu. A. Ivanov; N. L. Zaichenko; S. V. Rykov; O. Ya. Grinberg; A. A. Dubinskii; S. D. Pirozhkov; É. G. Rozantsev; I. E. Pokrovskaya; A. B. Shapiro
Conclusions1.The hydroxy, acyloxy, oxo, N-oxide oxo, and morpholino-oxo derivatives of 2,2,4-trimethyl-substituted 1,2,-di-and 1,2,3,4-tetrahydroquinolines have been synthesized. Their structure was confirmed by the IR and PMR spectra.2.The radicals formed during photolysis of a toluene solution of 2,2,4-trimethyl-8-hydroxy-1,2,3,4-tetrahydroquinoline as well as by oxidation of the acyl derivatives of 2,2,4-trimethyl-6-hydroxy-1,2,3,4-tetrahydroquinoline by meta-chloroperbenzoic acid were recorded and studied by the ESR method.
Russian Chemical Bulletin | 1982
L. A. Myshkina; F. M. Stoyanovich; E. D. Lubuzh; M. A. Ondar; O. Ya. Grinberg
Conclusions1.Syntheses were reported for 2,2,6,6-tetramethyl-4-hydroxy-4-alkylpiperidin-1-oxyls by the reaction of alkyllithium with triacetoneamine and subsequent oxidation of the piperidols formed using H2O2-Na2WO4.2.2,2,6,6-Tetramethyl-4-hydroxy-4-alkylpiperidines and the corresponding nitroxyl radicals were dehydrated by the action of sulfuric acid or POCl3 + C5H5N.3.IR spectroscopy indicated that 2,2,6,6-tetramethyl-4-hydroxy-4-alkylpiperidines have a boat conformation, while the corresponding nitroxyl radicals have a chain conformation.4.ESR spectroscopy in the 2-mm range gave the magnetic resonance parameters for the 2,2,6,6-tetramethyl-4-hydroxy-4-alkylpiperidin-1-oxyls prepared. A similarity in the basic configurations of the nitroxyl groups of these radicals and of 2,2,6,6-tetramethyl-4-hydroxy-4-methylpiperidin-1-oxyl was noted.
Archive | 1979
O. Ya. Grinberg; A. A. Dubinsky; A. P. Moravsky; V. F. Shuvalov; Ya. S. Lebedev
The special 2mm ESR technique was used to investigate HO2, radicals appearing at 77K photolysis of frozen H2O2/H2O2 solutions and RO2 radicals obtained by radiolisis of polytetraflubrobthylene. Slight differencies of g-values were detected which correlate with structure and stability of radicals. 2mm spectra proved to be sensitive to be sensitive to details of molecular motions