ABSTRACT In the present work we report the results of ab initio study, within GAUSSIAN 98, of a l... more ABSTRACT In the present work we report the results of ab initio study, within GAUSSIAN 98, of a large number of halogen, antimony and tin containing molecules and complexes. The calculations were carried out with the use of small and medium basis sets, i.e. 3-21G* (for halogens, antimony and tin) atoms and 6-31G* basis sets (for F, Cl and Br). To demonstrate the quality of the calculations the calculated bond length and quadrupole coupling constant (QCC) were compared with the corresponding experimental values for the compounds studied. With a few exceptions, the overall agreement with experiment is most satisfactory. The calculated NQCC values were used as a test of the quality of the wave functions. The results on Mössbauer chemical shifts are also in a good agreement with the experimental data, however, these quantities were measured only for a few compounds.
ABSTRACT 35Cl NQR spectra of substituted phenylisoxazoles and isoxazolines were analysed. For cer... more ABSTRACT 35Cl NQR spectra of substituted phenylisoxazoles and isoxazolines were analysed. For certain molecules the atom charges and orbital populations were calculated with the MINDO/3 method. It was proved that a chlorine atom at position 4 on an isoxazole ring transmits the influence from the phenyl ring at position 3 to the phenyl ring at position 5 on the isoxazole ring through the system of π-bonds.
ABSTRACT In our previous communication, density functional theory was used for QCC and isomer shi... more ABSTRACT In our previous communication, density functional theory was used for QCC and isomer shift calculations for halogen compounds and gave reliable results. Here we also employ the B3LYP/3-21G* method, which makes it possible to take into account all electrons of atoms constituting the molecules. QCC were estimated from the diagonal components of the electric field gradient tensor with a specially devised program.
The paper reports results of measurements of the ClKα shifts in the X-ray fluorescence spectra an... more The paper reports results of measurements of the ClKα shifts in the X-ray fluorescence spectra and 35Cl-NQR frequency for a group of tetrachloride titanium complexes. The experimental ClKα shifts were correlated with the parameters describing donor properties of ligands such as ligand strength (DN), ionisation potential (IP) or parameters of influence (P). Analysis of the correlation dependencies has indicated that
Two series of germanium compounds, (p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MP... more Two series of germanium compounds, (p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MPh3 (M = Ge (4), Sn (5)), were prepared using lithium or potassium intermediates. The changing of the reaction conditions results in trigermane Ph3Ge-Ge(SiMe3)2-GePh3 (6). The molecular structures of 1, 2, and 6 were investigated by X-ray analysis. By UV/visible spectroscopy it is established that introduction of a tin atom results in a significant bathochromic absorption shift. Furthermore, according to cyclic voltammetry, oxidation potentials decrease in the order 1 > 2 > 3. The electronic structures of 1–4 and related (Me3Si)3Ge-SiPh3 were investigated by DFT calculations. Fluorescence properties of 1–3 were studied in the solid state and in solution; for compound 3 phosphorescence (lifetime is 4.58 ms) is observed in the solid state.
Анализируется понятие «внеурочная деятельность» в школьном образовании. Охарактеризованы особенно... more Анализируется понятие «внеурочная деятельность» в школьном образовании. Охарактеризованы особенности внеурочной деятельности. Приведено понятие «внеурочная деятельность по химии», выделена ее цель и специфическая особенность на старшей ступени обучения в современной школе. Обоснована необходимость выполнения проектов по химии. Предложено одно из актуальных направлений: деятельность обучающихся по моделированию строения веществ. Описана методика работы обучающихся с программами Gaussian и GaussView, используемыми для решения задач квантово-механического моделирования молекулярных структур. Дана характеристика индивидуальным проектам по химии, приведены этапы их выполнения. Показан пример построения обучающимися молекулярных структур хлоридов 15-й группы периодической системы. Представлены результаты оценивания выполненных проектов на основе разработанных критериев и анкетирования с целью определения отношения обучающихся к компьютерному моделированию молекул.The analysis of the conce...
The journal of physical chemistry. A, Jan 27, 2017
The product of acetaldehyde and ammonia reaction, namely, 2,4,6-trimethyl-1,3,5-hexahydrotriazine... more The product of acetaldehyde and ammonia reaction, namely, 2,4,6-trimethyl-1,3,5-hexahydrotriazine trihydrate, was synthesized and identified using a combination of experimental (NMR spectroscopy, IR spectroscopy, melting point determination) and DFT-based theoretical approaches. A reaction mechanism was proposed. The reaction was shown to proceed via the formation of aminoalcohol, imine, and geminal diamine intermediates accompanied by cyclization of these species. The calculation results allowed us to build a potential energy surface of the acetaldehyde and ammonia interaction and determine the most energetically favorable pathway to yield acetaldehyde ammonia trimer. The reaction product was found in an energy minimum (-53.5 kcal/mol).
5th Korea-Russia International Symposium on Science and Technology. Proceedings. KORUS 2001 (Cat. No.01EX478), 2000
The main idea of the Townes-Dailey approximation is that the main contribution to the electric fi... more The main idea of the Townes-Dailey approximation is that the main contribution to the electric field gradient comes from valence electrons of the atom considered. Therefore, we expected that the best nuclear quadrupole coupling constants (QCC) values (i.e. the closest to the experimental results) could be calculated using a nuclear core pseudopotential. A good test of various non-empirical methods also could be the quality of reproduction of NQR parameters such as quadrupole coupling constants and asymmetry parameters. We used B3LYP functional in DFT calculations with 3-21G* and 6-311G** all-electron basis sets. On the other hand we used basis set II, which has a relativistic effective core potential with a (211/211/1) valence basis set for Ti, Nb, Sb, and Sn atoms, 6-311G** all-electron basis set for the H, C, N, S, P, O, Cl atoms. The QCC values have been calculated for diatomic halogens, interhalogens, trihalide ions, organohalogens, molecules and complexes containing B, Al, Ga, In, Sb, Sn, Ti and Nb atoms. The results presented in this work have been calculated use the Gaussian'98 package. The obtained correlation between experimental and calculated QCC values for halogen atoms are valid for all compounds studied, in spite of the different environment of the halogen atoms concerned. Analogous correlations were found for studied compounds containing B, Al, Ga, Sb and Nb atoms with use all-electron basis sets. The QCC values for such heavy atoms as I, Sb, Sn and Nb were close to zero from B3LYP/II calculations. The results confirmed that is impossible to obtain the QCC values for heavy atoms with the DFT performed using the pseudopotential methods
ABSTRACT In the present work we report the results of ab initio study, within GAUSSIAN 98, of a l... more ABSTRACT In the present work we report the results of ab initio study, within GAUSSIAN 98, of a large number of halogen, antimony and tin containing molecules and complexes. The calculations were carried out with the use of small and medium basis sets, i.e. 3-21G* (for halogens, antimony and tin) atoms and 6-31G* basis sets (for F, Cl and Br). To demonstrate the quality of the calculations the calculated bond length and quadrupole coupling constant (QCC) were compared with the corresponding experimental values for the compounds studied. With a few exceptions, the overall agreement with experiment is most satisfactory. The calculated NQCC values were used as a test of the quality of the wave functions. The results on Mössbauer chemical shifts are also in a good agreement with the experimental data, however, these quantities were measured only for a few compounds.
ABSTRACT 35Cl NQR spectra of substituted phenylisoxazoles and isoxazolines were analysed. For cer... more ABSTRACT 35Cl NQR spectra of substituted phenylisoxazoles and isoxazolines were analysed. For certain molecules the atom charges and orbital populations were calculated with the MINDO/3 method. It was proved that a chlorine atom at position 4 on an isoxazole ring transmits the influence from the phenyl ring at position 3 to the phenyl ring at position 5 on the isoxazole ring through the system of π-bonds.
ABSTRACT In our previous communication, density functional theory was used for QCC and isomer shi... more ABSTRACT In our previous communication, density functional theory was used for QCC and isomer shift calculations for halogen compounds and gave reliable results. Here we also employ the B3LYP/3-21G* method, which makes it possible to take into account all electrons of atoms constituting the molecules. QCC were estimated from the diagonal components of the electric field gradient tensor with a specially devised program.
The paper reports results of measurements of the ClKα shifts in the X-ray fluorescence spectra an... more The paper reports results of measurements of the ClKα shifts in the X-ray fluorescence spectra and 35Cl-NQR frequency for a group of tetrachloride titanium complexes. The experimental ClKα shifts were correlated with the parameters describing donor properties of ligands such as ligand strength (DN), ionisation potential (IP) or parameters of influence (P). Analysis of the correlation dependencies has indicated that
Two series of germanium compounds, (p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MP... more Two series of germanium compounds, (p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MPh3 (M = Ge (4), Sn (5)), were prepared using lithium or potassium intermediates. The changing of the reaction conditions results in trigermane Ph3Ge-Ge(SiMe3)2-GePh3 (6). The molecular structures of 1, 2, and 6 were investigated by X-ray analysis. By UV/visible spectroscopy it is established that introduction of a tin atom results in a significant bathochromic absorption shift. Furthermore, according to cyclic voltammetry, oxidation potentials decrease in the order 1 > 2 > 3. The electronic structures of 1–4 and related (Me3Si)3Ge-SiPh3 were investigated by DFT calculations. Fluorescence properties of 1–3 were studied in the solid state and in solution; for compound 3 phosphorescence (lifetime is 4.58 ms) is observed in the solid state.
Анализируется понятие «внеурочная деятельность» в школьном образовании. Охарактеризованы особенно... more Анализируется понятие «внеурочная деятельность» в школьном образовании. Охарактеризованы особенности внеурочной деятельности. Приведено понятие «внеурочная деятельность по химии», выделена ее цель и специфическая особенность на старшей ступени обучения в современной школе. Обоснована необходимость выполнения проектов по химии. Предложено одно из актуальных направлений: деятельность обучающихся по моделированию строения веществ. Описана методика работы обучающихся с программами Gaussian и GaussView, используемыми для решения задач квантово-механического моделирования молекулярных структур. Дана характеристика индивидуальным проектам по химии, приведены этапы их выполнения. Показан пример построения обучающимися молекулярных структур хлоридов 15-й группы периодической системы. Представлены результаты оценивания выполненных проектов на основе разработанных критериев и анкетирования с целью определения отношения обучающихся к компьютерному моделированию молекул.The analysis of the conce...
The journal of physical chemistry. A, Jan 27, 2017
The product of acetaldehyde and ammonia reaction, namely, 2,4,6-trimethyl-1,3,5-hexahydrotriazine... more The product of acetaldehyde and ammonia reaction, namely, 2,4,6-trimethyl-1,3,5-hexahydrotriazine trihydrate, was synthesized and identified using a combination of experimental (NMR spectroscopy, IR spectroscopy, melting point determination) and DFT-based theoretical approaches. A reaction mechanism was proposed. The reaction was shown to proceed via the formation of aminoalcohol, imine, and geminal diamine intermediates accompanied by cyclization of these species. The calculation results allowed us to build a potential energy surface of the acetaldehyde and ammonia interaction and determine the most energetically favorable pathway to yield acetaldehyde ammonia trimer. The reaction product was found in an energy minimum (-53.5 kcal/mol).
5th Korea-Russia International Symposium on Science and Technology. Proceedings. KORUS 2001 (Cat. No.01EX478), 2000
The main idea of the Townes-Dailey approximation is that the main contribution to the electric fi... more The main idea of the Townes-Dailey approximation is that the main contribution to the electric field gradient comes from valence electrons of the atom considered. Therefore, we expected that the best nuclear quadrupole coupling constants (QCC) values (i.e. the closest to the experimental results) could be calculated using a nuclear core pseudopotential. A good test of various non-empirical methods also could be the quality of reproduction of NQR parameters such as quadrupole coupling constants and asymmetry parameters. We used B3LYP functional in DFT calculations with 3-21G* and 6-311G** all-electron basis sets. On the other hand we used basis set II, which has a relativistic effective core potential with a (211/211/1) valence basis set for Ti, Nb, Sb, and Sn atoms, 6-311G** all-electron basis set for the H, C, N, S, P, O, Cl atoms. The QCC values have been calculated for diatomic halogens, interhalogens, trihalide ions, organohalogens, molecules and complexes containing B, Al, Ga, In, Sb, Sn, Ti and Nb atoms. The results presented in this work have been calculated use the Gaussian'98 package. The obtained correlation between experimental and calculated QCC values for halogen atoms are valid for all compounds studied, in spite of the different environment of the halogen atoms concerned. Analogous correlations were found for studied compounds containing B, Al, Ga, Sb and Nb atoms with use all-electron basis sets. The QCC values for such heavy atoms as I, Sb, Sn and Nb were close to zero from B3LYP/II calculations. The results confirmed that is impossible to obtain the QCC values for heavy atoms with the DFT performed using the pseudopotential methods
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