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81.
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84.
I. D. Sorokin O. L. Melnikova V. I. Pergushov D. A. Tyurin V. I. Feldman M. Ya. Melnikov 《Moscow University Chemistry Bulletin》2012,67(2):59-71
It has been established that, upon X-ray irradiation of various methyloxiranes in freonic matrices at 77 K, both open and cyclic (with the elongated C-C bond) forms of radical cations are stabilized. It has been shown that observed reversible photoinduced transformations of 2,3-dimethyloxirane and methyloxirane radical cations are related to the conversion between the open and cyclic forms of the radical cations with high quantum yields (0.02?C0.39, depending on the oxirane and the matrix). For the trimethyloxirane radical cation the action of light on the trans-isomer of the open form results in its photoinduced transformation into a C-centered radical with low quantum efficiency (??4 × 10?3). Tetramethyloxirane radical cations, stabilized in their open form, are resistant to the action of light. Probable causes of the observed effects are discussed. Upon the X-ray irradiation of 2,2-dimethyloxirane in freonic matrices at 77 K, a cyclic form of the radical cation is stabilized (presumably, as part of a complex with matrix molecules) which transforms into a distonic C-centered radical cation under the action of light with the quantum yield of ??10?3. 相似文献
85.
Ring Opening of Donor–Acceptor Cyclopropanes with the Azide Ion: A Tool for Construction of N‐Heterocycles 下载免费PDF全文
Konstantin L. Ivanov Dr. Elena V. Villemson Dr. Ekaterina M. Budynina Dr. Olga A. Ivanova Dr. Igor V. Trushkov Prof. Mikhail Ya. Melnikov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):4975-4987
A general method for ring opening of various donor–acceptor cyclopropanes with the azide ion through an SN2‐like reaction has been developed. This highly regioselective and stereospecific process proceeds through nucleophilic attack on the more‐substituted C2 atom of a cyclopropane with complete inversion of configuration at this center. Results of DFT calculations support the SN2 mechanism and demonstrate good qualitative correlation between the relative experimental reactivity of cyclopropanes and the calculated energy barriers. The reaction provides a straightforward approach to a variety of polyfunctional azides in up to 91 % yield. The high synthetic utility of these azides and the possibilities of their involvement in diversity‐oriented synthesis were demonstrated by the developed multipath strategy of their transformations into five‐, six‐, and seven‐membered N‐heterocycles, as well as complex annulated compounds, including natural products and medicines such as (?)‐nicotine and atorvastatin. 相似文献
86.
M. P. Samtsov S. A. Tikhomirov O. V. Buganov K. N Kaplevsky D. G. Melnikov L. S. Lyashenko 《Journal of Applied Spectroscopy》2009,76(6):783-790
Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments
where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene,
as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed
effects are interpreted within the framework of concepts on “burning out” a notch in the contour of a non-uniformly widened
vibronic band of S
0 → S
1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and
highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the
contact ion pairs that results in the formation of free radicals. 相似文献
87.
This article presents a generalized vector plane wave expansion method, applicable to isotropic and anisotropic periodic dielectric media of arbitrary geometry and dimension. The influence of anisotropic material orientation on the symmetry properties of photonic crystal dispersion surface is discussed. It is shown that the overall Brillouin zone symmetry is formed by the intersection of the photonic crystal lattice symmetry and the symmetry determined by the anisotropic material orientation. This work explains how to define the irreducible Brillouin zone of a two-dimensional anisotropic photonic crystal and demonstrates that doing it correctly allows one to avoid erroneous results, when calculating band gap diagrams of anisotropic photonic crystals. With the help of the methods presented, the possibility of controlling the band gaps of anisotropic photonic crystals by means of external electric field is shown. 相似文献
88.
Elizaveta N. Fisher Evgeny S. Melnikov Vladimir Gegeckori Natalya V. Potoldykova Dmitry V. Enikeev Kirill A. Pavlenko Snezana Agatonovic-Kustrin David W. Morton Galina V. Ramenskaya 《Molecules (Basel, Switzerland)》2022,27(22)
A novel HPLC-ESI-MS/MS method for simultaneous gonadotropin-releasing hormone (GnRH) analogs and somatostatin analog quantitation was developed and validated. The developed method was successfully applied to pharmacokinetic studies. The sample preparation process included solid-phase extraction (SPE). Effective chromatographic separation of the analytes and internal standard (dalargin) was achieved with a C18 column, using a gradient elution with two mobile phases: 0.1% v/v formic acid (aqueous solution) and 0.1% v/v formic acid (acetonitrile solution). The linearity of the method was demonstrated within a concentration range of 0.5–20 ng/mL, with correlation coefficients between 0.998–0.999 for goserelin, buserelin, triptorelin, and octreotide, respectively. The relative standard deviation (RSD, %) values for method accuracy and precision did not exceed 20% at the lower level of quantitation (LLOQ) or 15% at other concentration levels. 相似文献
89.
Yu. V. Kulvelis V. T. Lebedev D. Torok A. B. Melnikov 《Journal of Structural Chemistry》2007,48(4):740-746
Interaction of sulfonated scandium diphthalocyanine ScPc2(SO3)4(NH4)4 with DNA in water salt solutions was studied by small-angle neutron scattering, dynamic light scattering, and atomic force microscopy. The results provide evidence about packaging of DNA molecules and agree with previous viscosimetry and spectrophotometry data. 相似文献
90.
Melnikov A Radu I Bovensiepen U Krupin O Starke K Matthias E Wolf M 《Physical review letters》2003,91(22):227403
Coherent spin dynamics in the THz domain coupled to a coherent phonon is observed in the time-resolved second harmonic response of the Gd(0001) ferromagnetic metal surface. An LO phonon of 2.9 THz is excited by a transient charge displacement at the surface caused by resonant absorption of a fs laser pulse in the exchange-split surface state. This lattice vibration modulates the interlayer distance inducing a coherent variation of the exchange interaction between spins in adjacent layers. The resulting magnetization dynamics is considered as optical magnon wave packets coupled to the phonon. 相似文献