Gulnara Kuramshina | Lomonosov Moscow State University (original) (raw)
Papers by Gulnara Kuramshina
Russian Journal of Physical Chemistry A, 2007
ABSTRACT Quantum-mechanical calculations of the optimized structures, barriers to internal rotati... more ABSTRACT Quantum-mechanical calculations of the optimized structures, barriers to internal rotation about the Si-C bond, harmonic force fields, and vibrational frequencies of CCH3SiF3, CH2ClSiF3, CHCl2SiF3, and CCl3SiF3 were performed using the Hartree-Fock approximation and density functional theory at the MP2/6-31G*, B3LYP/6-31G*, B3LYP/6-311++G**, B3LYP/aug-cc-pVDZ, and B3LYP/aug-cc-pVTZ levels. A new interpretation of the infrared absorption and Raman spectra of the compounds was suggested on the basis of the theoretical results
Russian Journal of Physical Chemistry, 2006
ABSTRACT Without Abstract
Molecules, 2022
The model of Regularized Quantum Mechanical Force Field (RQMFF) was applied to the joint treatmen... more The model of Regularized Quantum Mechanical Force Field (RQMFF) was applied to the joint treatment of ab initio and experimental vibrational data of the four primary nucleobases using a new algorithm based on the scaling procedure in Cartesian coordinates. The matrix of scaling factors in Cartesian coordinates for the considered molecules includes diagonal elements for all atoms of the molecule and off-diagonal elements for bonded atoms and for some non-bonded atoms (1–3 and some 1–4 interactions). The choice of the model is based on the results of the second-order perturbation analysis of the Fock matrix for uncoupled interactions using the Natural Bond Orbital (NBO) analysis. The scaling factors obtained within this model as a result of solving the inverse problem (regularized Cartesian scale factors) of adenine, cytosine, guanine, and thymine molecules were used to correct the Hessians of the canonical base pairs: adenine–thymine and cytosine–guanine. The proposed procedure is ba...
Inverse Problems in Science and Engineering, 2020
The main mathematical results on the data processing in vibrational spectroscopy are presented. T... more The main mathematical results on the data processing in vibrational spectroscopy are presented. The approaches and algorithms proposed for molecular force field calculations have been constructed on a base of regularizing methods for solving nonlinear ill-posed problems and have been implemented in the software package SPECTRUM. These algorithms were used for constructing the regularized ab initio force fields of important biological molecules including the melatonin and Vitamin B6 derivatives.
Journal of Applied Spectroscopy, 1979
The products of codeposition of aluminum chloride and nitromethane were studied by low-temperatur... more The products of codeposition of aluminum chloride and nitromethane were studied by low-temperature IR spectroscopy (80200 K). Density functional (B3LYP/6-31G* and B3LYP/6-31+G**) quantum-chemical calculations of the geometry and vibrational frequencies of aluminum chloride, nitromethane, and AlCl 3 MeNO 2 and 2AlCl 3 MeNO 2 complexes were carried out. Comparison of the experimental and calculated IR spectra suggests that the preferred geometry of the 2AlCl 3 MeNO 2 complex is such that one AlCl 3 molecule is coordinated to an O atom of the nitro group, while the other AlCl 3 molecule forms an Al...Cl bridge.
Vibrational Spectroscopy, 2006
Geometrical optimization and frequency calculations on [HRh(CO) 4 ] were carried out using densit... more Geometrical optimization and frequency calculations on [HRh(CO) 4 ] were carried out using density functional theory methods with the B3LYP, PBE and B3PW91 functionals in conjunction with the LanL2DZ and DGDZVP basis sets. The accuracy of each calculation was verified by comparing the predicted and the experimentally obtained deconvoluted mid-infrared experimental C O stretching frequencies. The use of the density functional PBE with DGDZVP as the basis set was found to be the most accurate. The same method was then applied to [(C 2 H 5)CORh(CO) 4 ], [Rh 2 (CO) 6 (m-CO) 2 ], [Rh 4 (CO) 9 (m-CO) 3 ] and [Rh 6 (CO) 12 (m 3-CO) 4 ]. Again, vibrational spectral patterns and relative band intensities were in very good agreement with those experimentally observed after BTEM deconvolution. The only inconsistency was a constant shift in the predicted wavenumber assignments of ca. 1.5% for the terminal carbonyl stretching modes. In addition, the optimized geometries were also in good agreement with available X-ray structures of isolatable [Rh 4 (CO) 9 (m-CO) 3 ] and [Rh 6 (CO) 12 (m 3-CO) 4 ]. DFT not only proved to be a valuable tool in validating and confirming the structure of the reactive and unstable species but it also allowed better assignment of the observed spectra especially when vibrational modes were overlapping. The combination of advanced multi-component deconvolution, like band-target entropy minimization (BTEM), with DFT spectral prediction appears to have considerable potential for exploratory in situ studies of reactive rhodium carbonyl systems.
The Journal of Physical Chemistry A, 2009
Insulin-like growth factors (IGFs) are potent mitogens involved in the regulation of cell prolife... more Insulin-like growth factors (IGFs) are potent mitogens involved in the regulation of cell proliferation and apoptosis. The action of IGFs is mediated through a specific cell membrane receptor (IGF-IR), and the interactions between IGFs and this receptor are regulated by IGF-binding proteins (IGFBPs). IGFBP-3 is one such protein which either suppresses or enhances the actions of IGFs. Findings from most in vitro studies suggest that IGFBP-3 inhibits breast cancer cell growth and facilitates apoptosis, but clinical studies have found that high levels of IGFBP-3 in breast cancer tissues are associated with unfavourable prognostic indicators of the disease, such as large tumour size, low levels of steroid hormone receptors, elevated S-phase fraction and DNA aneuploidy. To further examine the role of IGFBP-3 in breast cancer recurrence and survival, we conducted the following nested case-control study. From a cohort of 1,000 women treated surgically for primary breast cancer, we consecutively selected 100 patients who developed recurrent disease after surgery and 100 age-and year of diagnosis-matched patients who had no relapse. Concentrations of IGFBP-3 in breast tissue extracts were determined with an ELISA. Inverse correlations of IGFBP-3 were revealed with estrogen receptor expression and patient age but not with tumour size or S-phase fraction. Levels of IGFBP-3 in breast tissues were slightly higher in the recurrent patients than in controls, but the differences were not statistically significant. No significant association was found between IGFBP-3 and breast cancer recurrence. Survival analysis, however, indicated that the risk of death was increased with higher IGFBP-3 levels, and the association was independent of other prognostic markers. In conclusion, our results demonstrate that high levels of IGFBP-3 are associated with unfavourable prognostic features of breast cancer.
The Journal of Chemical Thermodynamics, 1979
Structural Chemistry, 2010
Detailed studies of the molecular and electronic structures, vibrational frequencies, and infrare... more Detailed studies of the molecular and electronic structures, vibrational frequencies, and infrared intensities of [M −] and [M-H −] anions of aniline and its derivatives (2-, 3-, 4-fluoroanilines, N-[(2E)-1-methylbut-2-en-1-yl]aniline, (2-cyclopent-2-en-1-ylphenyl)amine, N-[(2E)-1-methylbut-2-en-1-yl]aniline, and N-cyclopent-2-en-1-ylaniline) have been carried out using the density functional method with UB3LYP functional and 6-31G** basis set augmented with sp diffuse functions on nitrogen, fluorine, and three carbon
Structural Chemistry, 2003
The infrared spectra (4000-400 cm −1) of solid and the Raman spectra (3500-30 cm −1) of liquid an... more The infrared spectra (4000-400 cm −1) of solid and the Raman spectra (3500-30 cm −1) of liquid and solid 1-nitropropane, CH 3 CH 2 CH 2 NO 2 , have been registered. Both the trans and gauche conformers have been identified in the fluid phase, while the trans form remains in the stable solid. Temperature dependence (190-230K) of the liquid 1-nitropropane Raman spectra has been carried out. From these data, the enthalpy difference was determined to be 870 ± 105 J-mol −1 , with the gauche conformer being the more stable rotamer. Ab initio and DFT calculations at different levels of approximation (HF, MP2, B3LYP, B3PW91) gave optimized geometries, harmonic force fields, and vibrational frequencies for the trans and gauche conformers. All the calculations (except the B3PW91/6-31G* level) predicted gauche as the low-energy conformer. Theoretical force constants are analyzed for formulating constraints in the molecular force field model of 1-nitropropane.
Russian Journal of Physical Chemistry A, 2010
Quantum mechanical calculations of optimized structures, harmonic force fields, and vibra tional ... more Quantum mechanical calculations of optimized structures, harmonic force fields, and vibra tional spectra were performed for 10 L glutamic acid conformers. The vibrational spectra were inter preted using B3LYP/6 31+G** calculations for the stablest conformer. Satisfactory agreement between the experimental and theoretical data was obtained. Vibrational frequency shifts caused by isotopic sub stitution of various types in the L glutamic acid molecule were analyzed taking into account the confor mational structure and the influence of water medium and molecule ionization. Isotopic tags are sug gested that can be used in biochemical studies taking into account their special characteristics.
Russian Journal of Physical Chemistry A, 2013
Quantum chemical calculations of the optimized structures, harmonic force fields, and frequen cie... more Quantum chemical calculations of the optimized structures, harmonic force fields, and frequen cies of 1 : 1 and 1 : 2 complexes of 2 (2' pyridyl) benzimidazole and 1 methyl 2 pyridine 2 yl 1H benzim idazole are performed by means of DFT (B3LYP/6 31+G**). The shifts in the frequencies of the vibrational spectra of the investigated complexes are considered with allowance for the conformational structure and effect of the medium. Analytical bands (spectral marks) are proposed that can be used to identify complexes of 2 (2' pyridyl) benzimidazole and 1 methyl 2 pyridine 2 yl 1H benzimidazole with water. It is con cluded that considering the environment within a model of a polarized continuum allows the forecasting of possible shifts in the frequencies in the vibrational spectra of the studied compounds in aqueous media and DMF.
Journal of Structural Chemistry, 1997
ABSTRACT
Journal of Structural Chemistry, 1997
ABSTRACT An inverse problem on calculating the force field parameters of a molecule from experime... more ABSTRACT An inverse problem on calculating the force field parameters of a molecule from experimental data and its solution using regularizing algorithms are considered The choice of a priori constraints that may be imposed on solutions of the inverse vibrational problem is analyzed in terms of quantum mechanical calculations of some polyatomic molecules at different levels of theory, including electron correlation.
Journal of Structural Chemistry, 1995
A new approach to the analysis of the force fields of polyatomic molecules is discussed. The resu... more A new approach to the analysis of the force fields of polyatomic molecules is discussed. The results of quantum chemical calculations in combination with experimental data are used in a regularizing procedure, where the nonempirical matrix of the force constants determines the stabilizer of Tikhonov's functional. The use of stable numerical methods allows the specific modeling of the force fields of polyatomic molecules with due account of rotational isomerism.
![Research paper thumbnail of Structures and vibrational spectra of 5H-dibenz[b,f]azepine and 5H-dibenzo[a,d]cycloheptene-5-ol on the basis of quantum mechanical calculations](https://attachments.academia-assets.com/87589573/thumbnails/1.jpg)
](Journal of Molecular Structure, 2003
Optimized geometries of NH-equatorial and NH-axial conformers of 5H-dibenz½b; f azepine and CH-eq... more Optimized geometries of NH-equatorial and NH-axial conformers of 5H-dibenz½b; f azepine and CH-equatorial and CH-axial conformers of 5H-dibenzo½a; dcyclohepten-5-ol have been obtained at the B3LYP and BLYP levels of the hybrid density functional theory with the 6-31G* and 6-31 þ G* basis sets. Corresponding ab initio calculations have also been performed at the HF/6-31G* level. For the investigated levels harmonic vibrational frequencies were calculated analytically. FT Raman (3200-200 cm 21) and infrared (3900-400 cm 21) spectra of 5H-dibenz½b; f azepine and 5H-diben-zo½a; dcyclohepten-5-ol have been recorded in the solid state and interpreted on a base of theoretical predictions.
Journal of Molecular Structure, 2000
Infrared and Raman spectra of 1,2-difluoro-1,1,2-trichloroethane (DFTCE) were measured in the gas... more Infrared and Raman spectra of 1,2-difluoro-1,1,2-trichloroethane (DFTCE) were measured in the gaseous, liquid and glassy states within a wide temperature interval. The complete assignment of the spectra was made on the basis of experimental information and theoretical (ab initio and DFT) force field calculations. It was found that in all aggregate states the substance existed as a mixture of three conformers, the most stable having trans-position of C–Cl bonds. Enthalpy differences between conformers in the gaseous phase were determined to be 1.93±0.25(t−g+),0.75±0.20(t−g−) and 1.09±0.20(g−−g+)kJmol−1. The potential function of internal rotation (PFIR) was estimated from the torsion fundamentals and calculated at the HF/6-31G∗ and B3LYP/6-31G∗ levels of theory.
Journal of Molecular Structure, 1997
M Mo on no og gr ra af fi ia as s A Am mb bi ie en nt ta ai is s I IS SS SN N: : 2 22 23 36 6-1 1... more M Mo on no og gr ra af fi ia as s A Am mb bi ie en nt ta ai is s I IS SS SN N: : 2 22 23 36 6-1 13 30 08 8 vo ol l. .
Journal of Molecular Structure, 1999
ABSTRACT Ab initio and DFT results on harmonic force constants for trans- and gauche-conformers o... more ABSTRACT Ab initio and DFT results on harmonic force constants for trans- and gauche-conformers of CH3CH2CH2Cl, CF3CH2CH2Cl and CCl3CH2CH2Cl are used for formulating constraints in molecular force field models described compounds with hindered internal rotation around the C–C bond.
Russian Journal of Physical Chemistry A, 2007
ABSTRACT Quantum-mechanical calculations of the optimized structures, barriers to internal rotati... more ABSTRACT Quantum-mechanical calculations of the optimized structures, barriers to internal rotation about the Si-C bond, harmonic force fields, and vibrational frequencies of CCH3SiF3, CH2ClSiF3, CHCl2SiF3, and CCl3SiF3 were performed using the Hartree-Fock approximation and density functional theory at the MP2/6-31G*, B3LYP/6-31G*, B3LYP/6-311++G**, B3LYP/aug-cc-pVDZ, and B3LYP/aug-cc-pVTZ levels. A new interpretation of the infrared absorption and Raman spectra of the compounds was suggested on the basis of the theoretical results
Russian Journal of Physical Chemistry, 2006
ABSTRACT Without Abstract
Molecules, 2022
The model of Regularized Quantum Mechanical Force Field (RQMFF) was applied to the joint treatmen... more The model of Regularized Quantum Mechanical Force Field (RQMFF) was applied to the joint treatment of ab initio and experimental vibrational data of the four primary nucleobases using a new algorithm based on the scaling procedure in Cartesian coordinates. The matrix of scaling factors in Cartesian coordinates for the considered molecules includes diagonal elements for all atoms of the molecule and off-diagonal elements for bonded atoms and for some non-bonded atoms (1–3 and some 1–4 interactions). The choice of the model is based on the results of the second-order perturbation analysis of the Fock matrix for uncoupled interactions using the Natural Bond Orbital (NBO) analysis. The scaling factors obtained within this model as a result of solving the inverse problem (regularized Cartesian scale factors) of adenine, cytosine, guanine, and thymine molecules were used to correct the Hessians of the canonical base pairs: adenine–thymine and cytosine–guanine. The proposed procedure is ba...
Inverse Problems in Science and Engineering, 2020
The main mathematical results on the data processing in vibrational spectroscopy are presented. T... more The main mathematical results on the data processing in vibrational spectroscopy are presented. The approaches and algorithms proposed for molecular force field calculations have been constructed on a base of regularizing methods for solving nonlinear ill-posed problems and have been implemented in the software package SPECTRUM. These algorithms were used for constructing the regularized ab initio force fields of important biological molecules including the melatonin and Vitamin B6 derivatives.
Journal of Applied Spectroscopy, 1979
The products of codeposition of aluminum chloride and nitromethane were studied by low-temperatur... more The products of codeposition of aluminum chloride and nitromethane were studied by low-temperature IR spectroscopy (80200 K). Density functional (B3LYP/6-31G* and B3LYP/6-31+G**) quantum-chemical calculations of the geometry and vibrational frequencies of aluminum chloride, nitromethane, and AlCl 3 MeNO 2 and 2AlCl 3 MeNO 2 complexes were carried out. Comparison of the experimental and calculated IR spectra suggests that the preferred geometry of the 2AlCl 3 MeNO 2 complex is such that one AlCl 3 molecule is coordinated to an O atom of the nitro group, while the other AlCl 3 molecule forms an Al...Cl bridge.
Vibrational Spectroscopy, 2006
Geometrical optimization and frequency calculations on [HRh(CO) 4 ] were carried out using densit... more Geometrical optimization and frequency calculations on [HRh(CO) 4 ] were carried out using density functional theory methods with the B3LYP, PBE and B3PW91 functionals in conjunction with the LanL2DZ and DGDZVP basis sets. The accuracy of each calculation was verified by comparing the predicted and the experimentally obtained deconvoluted mid-infrared experimental C O stretching frequencies. The use of the density functional PBE with DGDZVP as the basis set was found to be the most accurate. The same method was then applied to [(C 2 H 5)CORh(CO) 4 ], [Rh 2 (CO) 6 (m-CO) 2 ], [Rh 4 (CO) 9 (m-CO) 3 ] and [Rh 6 (CO) 12 (m 3-CO) 4 ]. Again, vibrational spectral patterns and relative band intensities were in very good agreement with those experimentally observed after BTEM deconvolution. The only inconsistency was a constant shift in the predicted wavenumber assignments of ca. 1.5% for the terminal carbonyl stretching modes. In addition, the optimized geometries were also in good agreement with available X-ray structures of isolatable [Rh 4 (CO) 9 (m-CO) 3 ] and [Rh 6 (CO) 12 (m 3-CO) 4 ]. DFT not only proved to be a valuable tool in validating and confirming the structure of the reactive and unstable species but it also allowed better assignment of the observed spectra especially when vibrational modes were overlapping. The combination of advanced multi-component deconvolution, like band-target entropy minimization (BTEM), with DFT spectral prediction appears to have considerable potential for exploratory in situ studies of reactive rhodium carbonyl systems.
The Journal of Physical Chemistry A, 2009
Insulin-like growth factors (IGFs) are potent mitogens involved in the regulation of cell prolife... more Insulin-like growth factors (IGFs) are potent mitogens involved in the regulation of cell proliferation and apoptosis. The action of IGFs is mediated through a specific cell membrane receptor (IGF-IR), and the interactions between IGFs and this receptor are regulated by IGF-binding proteins (IGFBPs). IGFBP-3 is one such protein which either suppresses or enhances the actions of IGFs. Findings from most in vitro studies suggest that IGFBP-3 inhibits breast cancer cell growth and facilitates apoptosis, but clinical studies have found that high levels of IGFBP-3 in breast cancer tissues are associated with unfavourable prognostic indicators of the disease, such as large tumour size, low levels of steroid hormone receptors, elevated S-phase fraction and DNA aneuploidy. To further examine the role of IGFBP-3 in breast cancer recurrence and survival, we conducted the following nested case-control study. From a cohort of 1,000 women treated surgically for primary breast cancer, we consecutively selected 100 patients who developed recurrent disease after surgery and 100 age-and year of diagnosis-matched patients who had no relapse. Concentrations of IGFBP-3 in breast tissue extracts were determined with an ELISA. Inverse correlations of IGFBP-3 were revealed with estrogen receptor expression and patient age but not with tumour size or S-phase fraction. Levels of IGFBP-3 in breast tissues were slightly higher in the recurrent patients than in controls, but the differences were not statistically significant. No significant association was found between IGFBP-3 and breast cancer recurrence. Survival analysis, however, indicated that the risk of death was increased with higher IGFBP-3 levels, and the association was independent of other prognostic markers. In conclusion, our results demonstrate that high levels of IGFBP-3 are associated with unfavourable prognostic features of breast cancer.
The Journal of Chemical Thermodynamics, 1979
Structural Chemistry, 2010
Detailed studies of the molecular and electronic structures, vibrational frequencies, and infrare... more Detailed studies of the molecular and electronic structures, vibrational frequencies, and infrared intensities of [M −] and [M-H −] anions of aniline and its derivatives (2-, 3-, 4-fluoroanilines, N-[(2E)-1-methylbut-2-en-1-yl]aniline, (2-cyclopent-2-en-1-ylphenyl)amine, N-[(2E)-1-methylbut-2-en-1-yl]aniline, and N-cyclopent-2-en-1-ylaniline) have been carried out using the density functional method with UB3LYP functional and 6-31G** basis set augmented with sp diffuse functions on nitrogen, fluorine, and three carbon
Structural Chemistry, 2003
The infrared spectra (4000-400 cm −1) of solid and the Raman spectra (3500-30 cm −1) of liquid an... more The infrared spectra (4000-400 cm −1) of solid and the Raman spectra (3500-30 cm −1) of liquid and solid 1-nitropropane, CH 3 CH 2 CH 2 NO 2 , have been registered. Both the trans and gauche conformers have been identified in the fluid phase, while the trans form remains in the stable solid. Temperature dependence (190-230K) of the liquid 1-nitropropane Raman spectra has been carried out. From these data, the enthalpy difference was determined to be 870 ± 105 J-mol −1 , with the gauche conformer being the more stable rotamer. Ab initio and DFT calculations at different levels of approximation (HF, MP2, B3LYP, B3PW91) gave optimized geometries, harmonic force fields, and vibrational frequencies for the trans and gauche conformers. All the calculations (except the B3PW91/6-31G* level) predicted gauche as the low-energy conformer. Theoretical force constants are analyzed for formulating constraints in the molecular force field model of 1-nitropropane.
Russian Journal of Physical Chemistry A, 2010
Quantum mechanical calculations of optimized structures, harmonic force fields, and vibra tional ... more Quantum mechanical calculations of optimized structures, harmonic force fields, and vibra tional spectra were performed for 10 L glutamic acid conformers. The vibrational spectra were inter preted using B3LYP/6 31+G** calculations for the stablest conformer. Satisfactory agreement between the experimental and theoretical data was obtained. Vibrational frequency shifts caused by isotopic sub stitution of various types in the L glutamic acid molecule were analyzed taking into account the confor mational structure and the influence of water medium and molecule ionization. Isotopic tags are sug gested that can be used in biochemical studies taking into account their special characteristics.
Russian Journal of Physical Chemistry A, 2013
Quantum chemical calculations of the optimized structures, harmonic force fields, and frequen cie... more Quantum chemical calculations of the optimized structures, harmonic force fields, and frequen cies of 1 : 1 and 1 : 2 complexes of 2 (2' pyridyl) benzimidazole and 1 methyl 2 pyridine 2 yl 1H benzim idazole are performed by means of DFT (B3LYP/6 31+G**). The shifts in the frequencies of the vibrational spectra of the investigated complexes are considered with allowance for the conformational structure and effect of the medium. Analytical bands (spectral marks) are proposed that can be used to identify complexes of 2 (2' pyridyl) benzimidazole and 1 methyl 2 pyridine 2 yl 1H benzimidazole with water. It is con cluded that considering the environment within a model of a polarized continuum allows the forecasting of possible shifts in the frequencies in the vibrational spectra of the studied compounds in aqueous media and DMF.
Journal of Structural Chemistry, 1997
ABSTRACT
Journal of Structural Chemistry, 1997
ABSTRACT An inverse problem on calculating the force field parameters of a molecule from experime... more ABSTRACT An inverse problem on calculating the force field parameters of a molecule from experimental data and its solution using regularizing algorithms are considered The choice of a priori constraints that may be imposed on solutions of the inverse vibrational problem is analyzed in terms of quantum mechanical calculations of some polyatomic molecules at different levels of theory, including electron correlation.
Journal of Structural Chemistry, 1995
A new approach to the analysis of the force fields of polyatomic molecules is discussed. The resu... more A new approach to the analysis of the force fields of polyatomic molecules is discussed. The results of quantum chemical calculations in combination with experimental data are used in a regularizing procedure, where the nonempirical matrix of the force constants determines the stabilizer of Tikhonov's functional. The use of stable numerical methods allows the specific modeling of the force fields of polyatomic molecules with due account of rotational isomerism.
Journal of Molecular Structure, 2003
Optimized geometries of NH-equatorial and NH-axial conformers of 5H-dibenz½b; f azepine and CH-eq... more Optimized geometries of NH-equatorial and NH-axial conformers of 5H-dibenz½b; f azepine and CH-equatorial and CH-axial conformers of 5H-dibenzo½a; dcyclohepten-5-ol have been obtained at the B3LYP and BLYP levels of the hybrid density functional theory with the 6-31G* and 6-31 þ G* basis sets. Corresponding ab initio calculations have also been performed at the HF/6-31G* level. For the investigated levels harmonic vibrational frequencies were calculated analytically. FT Raman (3200-200 cm 21) and infrared (3900-400 cm 21) spectra of 5H-dibenz½b; f azepine and 5H-diben-zo½a; dcyclohepten-5-ol have been recorded in the solid state and interpreted on a base of theoretical predictions.
Journal of Molecular Structure, 2000
Infrared and Raman spectra of 1,2-difluoro-1,1,2-trichloroethane (DFTCE) were measured in the gas... more Infrared and Raman spectra of 1,2-difluoro-1,1,2-trichloroethane (DFTCE) were measured in the gaseous, liquid and glassy states within a wide temperature interval. The complete assignment of the spectra was made on the basis of experimental information and theoretical (ab initio and DFT) force field calculations. It was found that in all aggregate states the substance existed as a mixture of three conformers, the most stable having trans-position of C–Cl bonds. Enthalpy differences between conformers in the gaseous phase were determined to be 1.93±0.25(t−g+),0.75±0.20(t−g−) and 1.09±0.20(g−−g+)kJmol−1. The potential function of internal rotation (PFIR) was estimated from the torsion fundamentals and calculated at the HF/6-31G∗ and B3LYP/6-31G∗ levels of theory.
Journal of Molecular Structure, 1997
M Mo on no og gr ra af fi ia as s A Am mb bi ie en nt ta ai is s I IS SS SN N: : 2 22 23 36 6-1 1... more M Mo on no og gr ra af fi ia as s A Am mb bi ie en nt ta ai is s I IS SS SN N: : 2 22 23 36 6-1 13 30 08 8 vo ol l. .
Journal of Molecular Structure, 1999
ABSTRACT Ab initio and DFT results on harmonic force constants for trans- and gauche-conformers o... more ABSTRACT Ab initio and DFT results on harmonic force constants for trans- and gauche-conformers of CH3CH2CH2Cl, CF3CH2CH2Cl and CCl3CH2CH2Cl are used for formulating constraints in molecular force field models described compounds with hindered internal rotation around the C–C bond.