Natalya V. Belova
Ivanovo State University of Chemistry and Technology
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Featured researches published by Natalya V. Belova.
Journal of Physical Chemistry A | 2008
Natalya V. Belova; Heinz Oberhammer; Georgiy V. Girichev; Sergey A. Shlykov
The tautomeric properties of alpha-chlorinated acetylacetone, 3-chloro-2,4-pentanedione CH3C(O)-CHCl-C(O)CH3, have been investigated by gas electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximations with different basis sets up to cc-pVTZ). Analysis of the GED intensities resulted in the presence of 100(2)% enol tautomer at 269(8) K. The following skeletal geometric parameters (rh1 values) of the molecule, which possesses Cs symmetry, were derived: r(C=C) = 1.378(3) A, r(C-C) = 1.450(3) A, r(C=O) = 1.243(3) A, r(C-O) = 1.319(3) A, r(O-H) = 1.001(4) A, r(C-Cl) = 1.752(4) A, angleC-C=C = 121.3(1.0) degrees , angleC=C-O = 119.9(1.2) degrees , angleC-C=O = 119.1(1.2) degrees . Due to very small contributions of the keto tautomer in alpha-chlorinated acetylacetone and its parent species, the effect of alpha-chlorination on tautomeric properties cannot be derived from experimental data. Quantum chemical calculations (B3LYP/6-31G**, B3LYP/cc-pVTZ, and MP2/cc-pVTZ) predict that alpha-chlorination of acetylacetone has no pronounced effect on the tautomeric properties. On the other hand, similar calculations for 1-chloro-1,3-butanedion, ClC(O)-CH2-C(O)CH3, demonstrate that chlorination in one beta position destabilizes the enol tautomer. In both chlorinated species the enol form is strongly preferred.
Journal of Organic Chemistry | 2014
Natalya V. Belova; Heinz Oberhammer; Nguen Hoang Trang; Georgiy V. Girichev
The tautomeric and structural properties of acetylacetone, CH3C(O)CH2C(O)CH3, have been studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to aug-cc-pVTZ). The analysis of GED intensities resulted in the presence of 100(3)% of the enol tautomer at 300(5) K and 64(5)% of the enol at 671(7) K. The enol tautomer possesses Cs symmetry with a planar ring and strongly asymmetric hydrogen bond. The diketo form possesses C2 symmetry. The experimental geometric parameters of both tautomeric forms are reproduced very closely by B3LYP/aug-cc-pVTZ and MP2/cc-pVTZ methods.
Journal of Structural Chemistry | 2003
N. I. Giricheva; Natalya V. Belova; G. V. Girichev; N. V. Tverdova; Sergey A. Shlykov; N. P. Kuz'mina; I. G. Zaitseva
A simultaneous electron diffraction and mass spectroscopic study of saturated vapors of erbium tris-dipivalylmethanate has revealed that at 136(5)°C, the vapor consists solely of Er(thd)3 molecules. Electron diffraction data may be described by two alternative models (of C_3 and D_3 symmetry), for which ra, rg, and rα structural parameters have been determined. D3 symmetry is recognized to be preferable for free Er(thd)3 molecules. The main structural parameters of the model are rα (Er − O) 2.218(5), rα (O − C) 1.279(5), rα (C − Cr) 1.404(6), rα (C − Ct) 1.512(3), rα(Ct − Cm) 1.542(5), rα (rm Cm− H) 1.804(4) Å, The ErO 75.0(0.4)°. The ErO6 coordination polyhedron has a structure close to an antiprism. A rotational angle of the O–O–O trigonal face relative to the position in a regular prism is 20.7(0.8)°. Possible reasons for the differences in the structure of Er(thd)3 molecules in the gas phase and crystal are discussed.
Journal of Structural Chemistry | 2002
Natalya V. Belova; N. I. Giricheva; G. V. Girichev; Sergey A. Shlykov; N. V. Tverdova; N. P. Kuz'mina; I. G. Zaitseva
Synchronous electron diffraction and mass spectrometric investigation of the saturated vapor of scandium tris-acetylacetonate was carried out. It was stated that at 155(5)°C the vapor contains only monomeric Sc(aa)3 molecules, whose structural parameters ra, rg, and rα were determined. The internuclear distances in the chelate ring were found to be rα(Sc–O) = 2.076(4) Å, rα(O–C) = 1.271(3) Å, rα(C–Cr) = 1.386(4) Å. The coordination polyhedron ScO6 has a nearly antiprism structure of D3 symmetry. The angle of rotation of the O–O–O trigonal faces relative to their position in a regular prism is 26.8(1.1)°.
Journal of Physical Chemistry A | 2012
Natalya V. Belova; Georgiy V. Girichev; Heinz Oberhammer; Trang Nguen Hoang; Sergey A. Shlykov
Tautomeric and structural properties of benzoylacetone, CH(3)-C(O)-CH(2)-C(O)-C(6)H(5), have been studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to aug-cc-pVTZ). Analysis of GED intensities resulted in the presence of 100% enol tautomer at 331(5) K. The existence of two possible enol conformers in about equal amounts is confirmed by both GED and quantum chemical results. In both conformers the enol ring possesses C(s) symmetry with a strongly asymmetric hydrogen bond. The experimental geometric parameters are reproduced very closely by the B3LYP/cc-pVTZ method.
Journal of Molecular Structure | 1995
N. I. Giricheva; Natalya V. Belova; Georgii V. Girichev; Sergey A. Shlykov
Abstract The molecular structure of bis(dipivaloylmethanato)copper(II) has been determined by sector-microphotometer gas electron diffraction. The experimental data are consistent with a monomeric square-planar structure with ∠OCuO = 93.7 ± 0.7°. The structural parameters are as follows: r g ( CuO ) = 1.916 ± 0.005 A , r g ( CO ) = 1.284 ± 0.009 A , r g ( CC ring ) = 1.399 ± 0.023 A , r g ( CC t ) = 1.581 ± 0.022 A , r g ( C t C m ) = 1.512 ± 0.006 A , r g ( C m H ) = 1.112 ± 0.009 A . The amplitudes of vibration have been calculated by a normal vibration treatment using a valence force field.
Journal of Physical Chemistry A | 2008
Natalya V. Belova; Heinz Oberhammer; Sergey A. Shlykov
The tautomeric and conformational properties of malonamic acid methyl ester, NH2C(O)-CH2-C(O)OCH3, have been investigated by means of gas-phase electron diffraction (GED) and quantum chemical calculations (HF, B3LYP, and MP2 approximations with different basis sets up to 6-311++G(3df,pd)). Both quantum chemistry and GED at 360(8) K result in the existence of a single diketo conformer in the gas phase. According to GED refinement, this conformer possesses an (ac, sc) conformation with dihedral angles C-C-C(NH2)=O of 140.3(3.0) degrees and C-C-C(OCH3)=O of 31.1(7.2) degrees. The experimental geometric parameters are reproduced very closely by MP2 and B3LYP methods with large basis sets.
Journal of Structural Chemistry | 2002
Natalya V. Belova; N. I. Giricheva; Georgiy V. Girichev; Sergey A. Shlykov; N. V. Tverdova; N. P. Kuz'mina; I. G. Zaitseva
Electron–diffraction and mass–spectrometric studies of saturated vapor of scandium tris–dipivaloyl–methanate showed that at 135(5)°, the vapor contains only monomeric Sc(thd)3, whose structural parameters ra, rg, and rα were determined. The internuclear distances in the chelate ring were found to be rαSc=O) = 2.066(5)Å, rα(O=C) = 1.272(3)Å, and rα(C=Cr) = 1.385(3)Å. The ScO6 coordination polyhedron has a D3 symmetry configuration close to a regular antiprism. The angle of rotation of the O=O=O trigonal faces relative to their position in a regular prism is 25.7(1.5)°.
Journal of Molecular Structure | 2018
Natalya V. Belova; Georgiy V. Girichev; Vitaliya E. Kotova; Kseniya A. Korolkova; Nguyen Hoang Trang
Abstract The molecular structure of 4-methylpiridine-N-oxide, 4-MePyO, has been studied by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both, quantum chemistry and GED analyses resulted in C S molecular symmetry with the planar pyridine ring. Obtained molecular parameters confirm the hyperconjugation in the pyridine ring and the sp2 hybridization concept of the nitrogen and carbon atoms in the ring. The experimental geometric parameters are in a good agreement with the parameters for non-substituted N-oxide and reproduced very closely by DFT calculations. The presence of the electron-donating CH3 substituent in 4-MePyO leads to a decrease of the ipso-angle and to an increase of r(N→O) in comparison with the non-substituted PyO. Electron density distribution analysis has been performed in terms of natural bond orbitals (NBO) scheme. The nature of the semipolar N→O bond is discussed.
Russian Journal of Inorganic Chemistry | 2011
G. V. Girichev; Natalya V. Belova; Nguen Hoang Trang; Sergey A. Shlykov; N. P. Kuz’mina
A mass spectrometric study of the overheated vapor over neodymium, erbium, ytterbium, and lutetium dipivaloylmethanates has been carried out. The mass spectra of these compounds depend significantly on the degree of overheating. This fact can be interpreted in terms of the variation of the concentration and chemical composition of metal-containing molecular species with vapor temperature. As the vapor temperature is raised from 200 to 700°C, the intensity of the molecular ion [M(thd)3]+ decreases relative to the [M(thd)2]+ ion intensity by approximately one order of magnitude for M = Er, Yb, and Lu and by two orders of magnitude for M = Nd. This finding is evidence in favor of the thermal decomposition of the lanthanide tris(dipivaloylmethanates) occurring via a two-step mechanism initially yielding the M(thd)2 radical.