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Nina I. Giricheva Georgiy V. Girichev Michail S. Fedorov Sergey N. Ivanov 《Structural chemistry》2013,24(3):807-818
A combined gas-phase electron diffraction/mass-spectrometric and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVTZ) study of the molecular structures of para-methylbenzenesulfonic acid (4-MBSA) and meta-nitrobenzenesulfonic acid (3-NBSA) was carried out. On the basis of mass spectrometric analysis, it was found that the substituted benzenesulfonic acids are thermostable at least up to 431(3) K. The fragmentations of 4-MBSA and 3-NBSA molecules under electron impact were analyzed. Quantum chemical calculations show that the 4-MBSA molecule exists as an enantiomeric pair, which is formed as a result of rotation of OH group about the S–O(H) bond. The 3-NBSA molecule has two conformers with different orientations of the O–H bond with respect to the nitro group and two corresponding enantiomers. The equilibrium configurations of 4-MBSA and both conformers of 3-NBSA have similar structures of the SO3H group, with the O–H bond eclipsing one of the S=O bonds. Selected experimental bond distances for 4-MBSA/3-NBSA are (Å) r h1(C–C)av = 1.403(3)/1.395(4); r h1(C–S) = 1.765(5)/1.784(5); r h1(S=O)av = 1.433(4)/1.438(4); and r h1(S–O) = 1.618(4)/1.620(4). The potential functions for the internal rotation of SO3H, OH, and CH3 or NO2 groups were calculated, and the transition states between enantiomers (conformers) were determined. The influence of substituent's nature on molecular geometry as well as on the energies of frontier orbitals and red-ox properties of the compounds is discussed. The inductive and mesomeric substituent effects were estimated from the donor–acceptor interaction energies of the natural bond orbitals of substituent and benzene frame. The correlation between group electronegativities and cooperative energetic characteristics of inductive and mesomeric effects of substituents is shown. 相似文献
114.
Shlykov SA Titov AV Oberhammer H Giricheva NI Girichev GV 《Physical chemistry chemical physics : PCCP》2008,10(42):6438-6445
The vapour over solid SeBr(4) at 10 degrees C was investigated with a combined gas-phase electron diffraction/mass spectrometric (GED/MS) method. The composition of the vapour derived from the mass spectra (43% SeBr(2), 56.7% Br(2) and 0.3% Se(2)Br(2)) was in agreement with the composition obtained from the analysis of the simultaneously recorded GED intensities (41(3)% SeBr(2), 59(3)% Br(2)). The GED study results in the following geometric parameters (r(g), angle(g) values with total uncertainties): Se-Br = 2.306(5) A and Br-Se-Br = 101.6(6) degrees . Most quantum chemical approximations (B3LYP, MP2, CCSD and CCSD(T) with relativistic effective core potentials and cc-pVTZ as well as aug-cc-pVTZ basis sets for the outer shells) overestimate the Se-Br bond length by 0.01 to 0.03 A. All methods reproduce the bond angle correctly, except for the B3LYP method. Gas phase vibrational frequencies estimated from experimental vibrational amplitudes agree well with those measured by Raman spectroscopy in acetonitrile solutions. All computational methods overestimate vibrational frequencies, especially that for the symmetric stretch vibration, by about or 8 to 13%. 相似文献
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G. V. Girichev N. V. Tverdova N. I. Giricheva E. D. Pelevina N. P. Kuz’mina O. V. Kotova 《Journal of Structural Chemistry》2010,51(1):23-31
Gas electron diffraction is used to study the structure of a zinc(II) N,N’-ethylene-bis(acetylacetoniminate) molecule, ZnO2N2C12H18, at a temperature T = 503(5) K. It is found that the molecule has the symmetry of the C2 equilibrium configuration with a nonplanar structure of the ZnN2O2 coordination fragment and internuclear distances rh1(Zn-O) of 1.958(13) ? and h1(Zn-N) of 2.012(16) ?. Quantum chemical calculations by the DFT/B3LYP/CEP,TZV method gives the molecular structure consistent
with that found in the experiment. 相似文献