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Статьи с участием сотрудников и пользователей РЦ

1) Статью с участием сотрудников РЦ поместили на обложку журнала Journal of Physical Organic Chemistry

Gorobets, N. Y.; Yermolayev, S. A.; Gurley, T.; Gurinov, A. A.; Tolstoy, P. M.; Shenderovich, I. G.; Leadbeater, N. E.

«Difference between 1H NMR signals of primary amide protons as a simple spectral index of the amide intramolecular hydrogen bond strength.»

J. Phys. Org. Chem. 2011, 25 (4), 287-295.
DOI: 10.1002/poc.1910

Abstract

The effect of the intramolecular H-bonding of the primary amide group on the spectral properties and reactivity of this group towards electrophiles has been studied in systematic rows of 1,2,5,6,7,8-hexahydro-7,7-dimethyl-2,5-dioxo-1-R-quinoline-3-carboxamides and 2-aryliminocoumarin-3-carboxamides using 1H and 15N NMR spectroscopy and the kinetics of model reactions. The upfield signal of the amide proton that is not intramolecularly H-bonded (Ha) depends on external factors such as solvent nature and concentration. At the same time, the downfield chemical shift of the Hb proton (bonded by the intramolecular hydrogen bond) depends mostly on the strength of the intramolecular H-bond, which is affected by such internal factor as electron nature of substituent R. The substituent’s influence on the Hb proton’s chemical shift is more effective in deuterochloroform medium than in DMSO-d6 where the intramolecular hydrogen bond is less stable. The value Δδ(H) = δ(Hb) − δ(Ha) is suggested as a simple comparative spectral index of the intramolecular hydrogen bond strength in these and similar compounds. By contrast, the effect of R on the H15N NMR chemical shift of the amide nitrogen has turned out to be too small to estimate changes of the electron density at the nitrogen. The effect of the intramolecular H-bond on the reactivity of the amide group is twofold. When the cleavage of the H-bond occurs on the rate limiting step it dramatically reduces the reaction rate. In the other case, the strengthening of the H-bond favors the reaction rate because of the increase of the electron density at the amide nitrogen.

2) Gurinov, A. A.; Mauder, D.; Akcakayiran, D.; Findenegg, G. H.; Shenderovich, I. G.

«Does Water Affect the Acidity of Surfaces? The Proton-Donating Ability of Silanol and Carboxylic Acid Groups at Mesoporous Silica.»

ChemPhysChem 2012, 13 (9), 2282-2285.
DOI: 10.1002/cphc.201200204

Solvation at the interphase:

A study of the influence of water on the effective acidity of silanol and carboxylic acid groups of propionic acid functionalized SBA-15 reveals that to affect the proton-donating ability of an acidic group at the surface, water should be able to form a solvation shell around that group. As a result, water does not affect the acidity of native SBA-15 but dramatically enhances that of SBA-15 functionalized with propionic acid moieties.

3) J. Guo, P. M. Tolstoy, B. Koeppe, N. S. Golubev, G. S. Denisov, S. N. Smirnov, H.-H. Limbach

«Hydrogen Bond Geometries and Proton Tautomerism of Homo-Conjugated Anions of Carboxylic Acids Studied via H/D Isotope Effects on 13C NMR Chemical Shifts»

J. Phys. Chem. A 2012, ASAP.
DOI: 10.1021/jp304943h.

Abstract:

Ten formally symmetric anionic OHO hydrogen bonded complexes, modeling Asp/Glu amino acid side chain interactions in nonaqueous environment (CDF3/CDF2Cl solution, 200–110 K) have been studied by 1H, 2H, and 13C NMR spectroscopy, i.e. intermolecularly H-bonded homoconjugated anions of acetic, chloroacetic, dichloroacetic, trifluoroacetic, trimethylacetic, and isobutyric acids, and intramolecularly H-bonded hydrogen succinate, hydrogen rac-dimethylsuccinate, hydrogen maleate, and hydrogen phthalate. In particular, primary H/D isotope effects on the hydrogen bond proton signals as well as secondary H/D isotope effects on the 13C signals of the carboxylic groups are reported and analyzed. We demonstrate that in most of the studied systems there is a degenerate proton tautomerism between O-H···O and O···H–O structures which is fast in the NMR time scale. The stronger is the proton donating ability of the acid, the shorter and more symmetric are the H-bonds in each tautomer of the homoconjugate. For the maleate and phthalate anions exhibiting intramolecular hydrogen bonds, evidence for symmetric single well potentials is obtained. We propose a correlation between H/D isotope effects on carboxylic carbon chemical shifts and the proton transfer coordinate, q1 =1/2(rOH – rHO), which allows us to estimate the desired OHO hydrogen bond geometries from the observed 13C NMR parameters, taking into account the degenerate proton tautomerism.

4) B. C. K. Ip, I. G. Shenderovich, P. M. Tolstoy, J. Frydel, G. S. Denisov, G. Buntkowsky and H.-H. Limbach,

«NMR Studies of Solid Pentachlorophenol-4-Methylpyridine Complexes Exhibiting Strong OHN Hydrogen Bonds: Geometric H/D Isotope Effects and Hydrogen Bond Coupling Cause Isotopic Polymorphism»

J. Phys. Chem. A 2012, ASAP.
DOI: 10.1021/jp305863n.

Abstract:

We have studied the hydrogen bond interactions of 15N labeled 4-methylpyridine (4-MP) with pentachlorophenol (PCP) in the solid state and in polar solution using various NMR techniques. Previous spectroscopic, X-ray, and neutron crystallographic studies showed that the triclinic 1:1 complex (4-MPPCP) exhibits the strongest known intermolecular OHN hydrogen bond in the solid state. By contrast, deuteration of the hydrogen bond gives rise to the formation of a monoclinic structure exhibiting a weaker hydrogen bond. By performing NMR experiments at different deuterium fractions and taking advantage of dipolar 1H–15N recoupling under combined fast MAS and 1H decoupling, we provide an explanation of the origin of the isotopic polymorphism of 4-MPPCP and improve previous chemical shift correlations for OHN hydrogen bonds. Because of anharmonic ground state vibrations, an ODN hydrogen bond in the triclinic form exhibits a shorter oxygen–hydron and a longer oxygen–nitrogen distance as compared to surrounding OHN hydrogen bonds, which also implies a reduction of the local dipole moment. The dipole–dipole interaction between adjacent coupled OHN hydrogen bonds which determines the structure of triclinic 4-MPPCP is then reduced by deuteration, and other interactions become dominant, leading to the monoclinic form. Finally, the observation of stronger OHN hydrogen bonds by 1H NMR in polar solution as compared to the solid state is discussed.

5) Принята к печати статья в журнале Solid State Phenomena

E. Kurenkova, A. Vyvodtseva, M. G. Shelyapina, V. I. Chizhik, A. V. Ievlev, N. E. Skryabina, A. G. Aleksanyan, D. Fruchart

"1H NMR study of hydrogen site occupancy in hydrides of disordered Ti-V and Ti-V-Cr alloys"

Solid State Phenomena, 2012.

6) А. Б. Никольский, Ю. С. Варшавский, Т. Г. Черкасова, И. С. Подкорытов, В. А. Гиндин

"Межфрагментная передача электронных эффектов π-акцепторных лигандов в гетерометаллических триадных комплексах с центральным звеном trans-[Ru(Py)4(CN)2]"

Известия Академии наук. Серия химическая, 2012, № 4, стр. 810.