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Archive for A. Grevtsev

08 Nov 2017
Acknowledging publications • Publications

Carbohydrate Polymers, 2017, 169, 117–126

N.G. Voron’ko, S.R. Derkach, M.A. Vovk, P.M. Tolstoy

“Complexation of κ-carrageenan with gelatin in the aqueous phase analysed by 1H NMR kinetics and relaxation”

Carbohydrate Polymers, 2017, 169, 117–126
DOI: 10.1016/j.carbpol.2017.04.010

The 1H NMR spectroscopy is used to study the kinetics of gelation in the aqueous mixtures of κ-carrageenan with gelatin. The time dependence of NMR signals intensities shows that the kinetics of gel formation consists of classical ‘fast’ (rate constant k ≈ 6 h−1) and ‘slow’ (k ≈ 1 h−1) periods, corresponding to a coil → helix transition and subsequent aggregation of helices. Upon increase of the κ-carrageenan/gelatin (w/w) ratio Z the rate of the fast process slows down by a factor of 1.6–2.4. Further analysis was done by studying the dependence of spin-spin relaxation times of protons of gelatin on Z in the aqueous phase. A qualitative scheme describing hydrogel formation in the complex solution is given. It is hypothesized that at higher concentration of PECs the hydrogel structure network is stabilized by three types of nodes: triple helices of gelatin and intra-/inter-molecular double helices of κ-carrageenan.

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04 Nov 2017
Process

October

Total in October 2347 service applications were carried out.
All together measured:

  • 2218 1H spectra
  • 366 13C spectra
  • 95 DEPT spectra
  • 63 COSY spectra
  • 19 NOESY spectra
  • 52 31P spectra
  • 169 19F spectra

242 applications were carried out.

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30 Oct 2017
Acknowledging publications

Green Chemistry, 2017, 19, 3032–3041

G. Werner, K.S. Rodygin, A.A. Kostin, E.G. Gordeev, A.S. Kashin, V.P. Ananikov

“A solid acetylene reagent with enhanced reactivity: fluoride-mediated functionalization of alcohols and phenols”

Green Chemistry, 2017, 19, 3032–3041
DOI: 10.1039/C7GC00724H

source: http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC00724H#!divAbstract

The direct vinylation of an OH group in alcohols and phenols was carried out utilizing a novel CaC2/KF solid acetylene reagent in a simple K2CO3/KOH/DMSO system. The functionalization of a series of hydroxyl-group-containing substrates and the post-modification of biologically active molecules were successfully performed using standard laboratory equipment, providing straightforward access to the corresponding vinyl ethers. The overall process developed involves an atom-economical addition reaction employing only inorganic reagents, which significantly simplifies the reaction set-up and the isolation of products. A mechanistic study revealed a dual role of the F− additive, which both mediates the surface etching/renewal of the calcium carbide particles and activates the C[triple bond, length as m-dash]C bond towards the addition reaction. The development of the fluoride-mediated nucleophilic addition of alcohols eliminates the need for strong bases and may substantially extend the areas of application of this attractive synthetic methodology due to increasing functional group tolerance. As a replacement for dangerous and difficult to handle high-pressure acetylene, we propose the solid reagent CaC2/KF, which is easy to handle, does not require dedicated laboratory equipment and demonstrates enhanced reactivity of the acetylenic triple bond. Theoretical calculations have shown that fluoride-mediated activation of the hydroxyl group towards nucleophilic addition significantly reduces the activation barrier and facilitates the reaction.

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19 Oct 2017
Acknowledging publications • Publications

Science of The Total Environment 2018, 615, 1229–1238

R. Vasilevich, E. Lodygina, V. Beznosikova, E. Abakumov

“Molecular composition of raw peat and humic substances from permafrost peat soils of European Northeast Russia as climate change markers”

Science of The Total Environment 2018, 615 (In Progress, Available online 17 October 2017), 1229–1238
DOI: 10.1016/j.scitotenv.2017.10.053

source: http://www.sciencedirect.com/science/article/pii/S0048969717327560

Humic substances (HSs) from the mire peat soils of the forest-tundra zone of the European northeast part of Russia have been characterized in terms of molecular composition. This was accomplished using solid-state 13C nuclear magnetic resonance (13C NMR) techniques and electron spin resonance (ESR) spectroscopy. The composition depended on the intensity of cryogenic processes in the active layer, the quality of the humification precursors (the degree of peat material transformation), and the biochemical selection of aromatic fragments during humification. Humic acids (HAs) and fulvic acids (FAs) of the peat soils showed the presence of compounds with a low extent of condensation and a low portion of aromatic fragments, which increased with depth. A higher proportion of aliphatic carbon species was found in the HAs, indicating a low degree of organic matter stabilization. Based on the data from the two types of peat soils, we suggest that particular changes in the proportion of aromatic and unoxidized aliphatic fragments on the border of the bottom of the active layer and permafrost layers can be used as markers of current climatic change.

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13 Oct 2017
Acknowledging publications • Publications

Journal of Molecular Structure, 2017, 1146, 554–561

A. M. Afanasenko, D. V. Boyarskaya, I. A. Boyarskaya, T. G. Chulkova, Y. M. Grigoriev, I. E. Kolesnikov, M. S. Avdontceva, T. L. Panikorovskii, A. I. Panin, A. N. Vereshchagin, M. N. Elinson

“Structures and photophysical properties of 3,4-diaryl-1H-pyrrol-2,5-diimines and 2,3-diarylmaleimides”

Journal of Molecular Structure, 2017, 1146, 554–561
DOI: 10.1016/j.molstruc.2017.06.048

source: http://www.sciencedirect.com/science/article/pii/S0022286017308293

Structural features of 3,4-diaryl-1H-pyrrol-2,5-diimines and their derivatives have been studied by molecular spectroscopy techniques, single-crystal X-ray diffraction, and DFT calculations. According to the theoretical calculations, the diimino tautomeric form of 3,4-diaryl-1H-pyrrol-2,5-diimines is more stable in solution than the imino-enamino form. We also found that the structurally related 2,3-diarylmaleimides exist in the solid state in the dimeric diketo form. 3,4-Diaryl-1H-pyrrol-2,5-diimines and 2,3-diarylmaleimides exhibit fluorescence in the blue region of the visible spectrum. The fluorescence spectra have large Stokes shifts. Aryl substituents at the 3,4-positions of 1H-pyrrol-2,5-diimine do not significantly affect fluorescence properties. The insertion of donor substituents into 2,3-diarylmaleimides leads to bathochromic shift of emission bands with hyperchromic effect.

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10 Oct 2017
Daybook

Delegation from Thailand

source: https://spbu.ru/press-center/press-relizy/princessa-tailanda-maha-chakri-sirindon-posetila-nauchnyy-park-spbgu

The delegation led by the Princess Maha Chakri Sirindhorn of Thailand has visited St Petersburg University. The delegation visited some of the Resource Centres. the Director of the Magnetic Resonance Research Centre (CMR) Petr Tolstoy has presented main research methods realized in CMR. Peter Tolstoy also has told about collaboration experience in research with the foreign scientists.
More about visit of the delegation

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04 Oct 2017
Process

September

Total in September 1938 service applications were carried out.
All together measured:

  • 1821  1H spectra
  • 296  13C spectra
  • 72  DEPT spectra
  • 22  COSY spectra
  • 22  NOESY spectra
  • 27  31Р spectra
  • 142  19F spectra

219 applications were carried out.

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25 Sep 2017
Daybook

Processing NMR spectra on mobile devices

source: http://resources.mestrelab.com/mnova-tablet-getting-started-guide/#prettyPhoto/13/
The Mnova NMR tablet application was designed for processing NMR spectra with touch-controlled Android and iPad devices. Free version of this application is available in Google Play store and App Store.

Starting Guide to Mnova tablet

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19 Sep 2017
Acknowledging publications

Tetrahedron Letters, 2017, 58, 3353–3357

S. Miltsov, V. Karavan, A. Misharev, G. Starova, J. Alonso-Chamarro, M. Puyol

“Unprecedented acid-catalyzed Wurtz-type coupling of meso-bromoindodicarbocyanine dyes”

Tetrahedron Letters, 2017,58, 3353–3357
DOI: 10.1016/j.tetlet.2017.07.043

source: http://www.sciencedirect.com/science/article/pii/S0040403917308894

meso-Bromosubstituted indodicarbocyanine dyes produce dimeric molecules, together with the debrominated species, under acid catalysis. The relationship between the dimerization and hydrodebromination routes depends on the aryl substitution of the dyes. A possible reaction mechanism is also proposed.

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05 Sep 2017
Daybook

Photo-session


A photo-session of the working process was held in the CMR.

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