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Vokin A. I. Sherstyannikova L. V. Krivoruchka I. G. Aksamentova T. N. Krylova O. V. Turchaninov V. K. 《Russian Journal of General Chemistry》2003,73(6):973-984
4(5)-Nitroimidazole in solution is stabilized as the 5-nitro isomer due to formation of hydrogen bond with an aprotic protophilic solvent. Amphiprotic medium favors displacement of the tautomeric equilibrium toward the 4-nitro isomer via formation of a solvate complex where 4-nitroimidazole acts as hydrogen bond acceptor. The observed specific solvatochromic effect in the UV spectrum of 4-nitroimidazole and related heterocyclic nitro compounds is determined by the electronic configuration of the excited ,*-state. 相似文献
13.
Turchaninov V. K. Murzina N. M. Vokin A. I. Aksamentova T. N. Trofimov B. A. 《Russian Journal of General Chemistry》2001,71(2):234-242
IR and UV spectrosocopy and quantum chemistry were used to reveal a bifurcate (three-center) hydrogen bond in the complexes of 2-(1,2,2-tricyanovinyl)pyrrole with hydrogen-bond acceptors. In the gas phase and aprotic inert solvents this compound exists predominantly as the sp conformer stabilized by intra- molecular hydrogen bond involving an orthogonal system of the nitrile group and the NH hydrogen. The formation of the three-center hydrogen bond with an aprotic protophilic solvent shifts the conformational equilibrium to the ap conformer. As the strength of the intermolecular hydrogen bond increases in the series nitromethane < acetonitrile < dioxane, the fraction of the ap conformer increases and becomes prevailing already in the moderately protophilic THF. Solvatochromism of the long-wave absorption band in the elec- tronic spectra of the sp and ap conformers was studied in detail. 相似文献
14.
A. I. Vokin Yu. L. Frolov S. A. Medvedev S. G. D'yachkova 《Russian Chemical Bulletin》1993,42(10):1680-1683
The electronic structure ofo-methoxy(hydroxy)-substituted benzenes has been investigated by the combined use of photoelectron spectroscopy and molecular
orbital calculations by means of the semi-empirical AM1 method. Absorption bands in the PE spectra have been assigned, the
dependence of someπ-orbital energies on the molecular conformation has been found, and the estimation of the mean torsion angle of the OCH3-group with the plane of the benzene ring has been carried out. The results obtained show that the gas-phase conformations
of the heavy-atom framework of guaiacol and vanillin molecules are planar. For veratrole and veratraldehyde, nonplanar conformations
with mean torsion angles ϕ ≈ 80° and 55°, respectively, have been observed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1757–1760, October, 1993. 相似文献
15.
A. I. Vokin L. M. Sinegovskaya A. M. Shulunova V. K. Turchaninov 《Optics and Spectroscopy》2013,114(5):720-728
IR spectroscopic data are used to demonstrate that the donor ability of alcohols in H-bonds is determined by the molecular conformation and the universal interaction of subunits of the H-bond complex in homological series. The observed regularities can be employed for empirical separation of the contributions of electrostatic and covalent components in the formation energy of the H-complex. 相似文献
16.
Deep-lying π- and σ-orbitals of 10-alkylphenothiazines were studied by photoelectron spectroscopy and quantum-chemical AM1
calculations. It was demonstrated that in 10-ethylphenothiazine the lone electron pair of the S atom interacts with the π-system
of the aromatic fragments. The π-MOs, whose energies are a function of the dihedral angle between the planes of the benzene
rings of phenothiazines and are independent of the degree of pyramidality of the N atom, were found. The differences in the
energy of these MOs were used for estimating equilibrium dihedral angles of tricyclic molecules in the gaseous phase. These
values differ only slightly from those observed in the solid phase. The replacement of the hydrogen atom at position 10 by
the methyl group leads to a decrease in the dihedral angle, leaving the orientation of the substituent unchanged. The orbital
energies of phenothiazines, which were calculated by the AM1 method, adequately reflect the order of changes in the ionization
potential. However, contributions of the two highest occupied π-MOs to the total charges on the N and S atoms are inconsistent
with the experimental data.
For Part 10, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1542–1548, August, 1998. 相似文献
17.
Turchaninov V. K. Murzina N. M. Vokin A. I. Trofimov B. A. 《Russian Journal of General Chemistry》2001,71(11):1701-1707
Rotational isomerism of 2-(tricyanovinyl)-5-phenylpyrrole and formation of complexes with a three-centered (bifurcational) hydrogen bond were studied by UV spectroscopy and quantum-chemical calculations. In the gas phase and in weakly and moderately protophilic media these compounds have mainly the syn-periplanar form stabilized by the intramolecular hydrogen bond involving the orthogonal system of the nitrile group and the NH hydrogen atom. No intermolecular H complex is formed in such solvents. In tetrahydrofuran, cyclohexanone, pyridine, and some other media a complex conformational equilibrium is observed. Interaction with aliphatic alcohols, amides, dimethyl sulfoxide, and triethylamine results in stabilization of the H complex of the anti-periplanar conformer. 相似文献
18.
Interaction of the triplet state of chloranil with durene in dioxane leads to the formation of short-lived polar complexes with a 11 composition (exciplex) and a 12 composition (terplex). One of the channels for destruction of the terplex is proton transfer between its counterions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1295–1299, June, 1990. 相似文献
19.
Turchaninov V. K. Vokin A. I. Aksamentova T. N. Krivoruchka I. G. Shulunova A. M. Andriyankova L. V. 《Russian Journal of General Chemistry》2003,73(5):743-752
The effects of aprotic inert media on the electronic absorption spectra of aromatic nitro compounds p-NO2C6H4R were used as evidence for the linear correlation between the slope s
a of the solvatochromism equations max = 0 + s
a* and the dipole moments of the molecules in their ground electronic state g. A linear correlation was established between 0 and the first ionization potential of subunits C6H5R. A new approach to estimating the dipole moment of electronically excited molecules (e) for molecules like p-NO2C6H4R on the basis of the correlation e = rg was proposed. 相似文献
20.
V. K. Turchaninov A. I. Vokin D. -S. D. Toryashinova S. E. Korostova 《Russian Chemical Bulletin》1993,42(5):822-826
The characteristics of photoelectron (PE) spectra of 2-phenylpyrroles and biphenyls have been correlated with the UV spectroscopy data for their radical cations. The geometric and electronic structures of the compounds and radical cations have been calculated using the AM1 method. The absorption bands of the radical cations observed in the visible region of spectrum have been found to pertain to the quasi-Koopmans type,i.e., they are realized between the doubly and partially occupied -MO, but their energies differ strongly from those calculated on the basis of PE spectra. This is explained by the distinction between the spatial structure of a molecule and that of the respective radical cation. The second cause of the discrepancy between the data of the two spectral methods consists in orbital — interactions, which are most conspicuous in the case of 4(4)-halogen-substituted compounds.For Part 4 see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 869–874, May, 1993. 相似文献