The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and ...The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and transition states involved in this reaction have been optimized at the （U）B3LYP/6-31＋G（d,p） level, and then their accurate relative energies have been improved using the G3MP2B3 method. The potential energy profile is confirmed via intrinsic reaction coordinate calculations of transition states. Four possible production channels are examined respectively, as H＋ transfer, H-atom transfer, H2＋ transfer, and bi- molecular nucleophilic substitution （SN2） reaction pathways. Based on present calculations, the H2＋ transfer reaction is major among these four channels, which agrees with previous experimental conclusions.展开更多
Using geometry optimization and DFT method at the B3LYP/6-31G* level for C20H10, an equilibrium geometry is identified to have the form of polyhedral hydrocarbon with five carbon-carbon single bonds linking two pentap...Using geometry optimization and DFT method at the B3LYP/6-31G* level for C20H10, an equilibrium geometry is identified to have the form of polyhedral hydrocarbon with five carbon-carbon single bonds linking two pentaprismane cages. Thus, C20H10 is a tri-cage molecule with three pentaprismane cages. Vibrational frequencies and infrared spectrum are computed at the same level. The heat of formation for this molecule has also been estimated in this paper.展开更多
The crystal structure of the title compound, diethyl 4,5-di（thienyl）-3,6-bis（trime- thylsilyl）phthalate （C26H3404S2Si2, Mr = 530.83）, has been determined by single-crystal X-ray diffraction. The crystal belongs ...The crystal structure of the title compound, diethyl 4,5-di（thienyl）-3,6-bis（trime- thylsilyl）phthalate （C26H3404S2Si2, Mr = 530.83）, has been determined by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pccn with a = 43.008（5）, b = 10.9000（12）, c = 11.9357（14） A, V= 5595.3（11） A3, Z = 8, F（000） = 2256, Dc= 1.260 mg/m3, p = 0.305 mm-1, T = 113（2） K, S = 1.090, R = 0.0413 and wR = 0.0969 for 5952 observed reflections with 1 〉 2o（/）. The benzene ring system is planar and makes dihedral angles of 63.7（2） and 72.5（4） with the two thienyl rings A （C（23）-C（26）, S（2）） and B （C（19）-C（22）, S（1））, respectively. The UV-vis absorption and fluorescence of the title compound were discussed. The molecular structure of the title compound has been optimized using DFT method at the B3LYP/6-31G（d） level. The computational results showed that the optimized geometer parameters are consistent well with the experiment data. The vertical ionization potential, vertical electron affinity and frontier orbitals were also discussed.展开更多
Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 （D6） and C24O have been performed using density functional theory （DFT） method. The geometric and electronic ...Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 （D6） and C24O have been performed using density functional theory （DFT） method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G（d） level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.展开更多
The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully ...The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G（d,p） and G3MP2B3 levels, respectively. Based on the B3LYP/6- 31G（d,p） optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G（d,p） level. Isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and a-complex structure has the highest energy and will not exist.展开更多
Theoretical studies on a series of oligobenzothiophenes were carded out with the AM 1 and DFT methods. Based on B3LYP/6-31G（D） optimized geometries, the electronic spectra, IR spectra and NMR spectra of the oligomer...Theoretical studies on a series of oligobenzothiophenes were carded out with the AM 1 and DFT methods. Based on B3LYP/6-31G（D） optimized geometries, the electronic spectra, IR spectra and NMR spectra of the oligomers were calculated by INDO/CIS, AM1 and B3LYP/6-31G（D） methods, respectively. The energy gaps decrease, and the absorption in elec- tronic spectra exhibits a red-shift as polymerization increases. The IR frequencies are little affected by the polymerization and substituents. The ^13C chemical shifts are changed to be upfield since the electron-donating groups increase the electron density of carbon atoms but remain unchanged with the increase of polymerization.展开更多
Theoretical investigation on the highest epoxygenated fullerene C36018 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G（d） level. Their equilibrium structures, thermal st...Theoretical investigation on the highest epoxygenated fullerene C36018 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G（d） level. Their equilibrium structures, thermal stabilities, electronic structures, vertical ionization potentials, vertical electron affinities, vibrational frequencies and 13C NMR chemical shifts have been studied. The calculation results showed that C36O18 isomers have higher LUMO-HOMO energy gaps than the fullerene C36 and should be more stable. Compared with C36, it is less possible for C36O18 to accept or donate electrons from reduced VEAs and enhanced VIPs. It has been found that C36O18 isomers are not aromatic at all or antiaromatic on analyzing the NICS values. The present study will encourage further theoretical and experimental analyses of this system in future.展开更多
Density functional theory (DFT) has been applied to study the enantioselective reduction of 3-morpholin-4-yl-1-phenyl-1-propanone with borane catalyzed by (S)-4-benzyl-5,5- diphenyl-1,3,2-oxazaborolidine at the B3LY...Density functional theory (DFT) has been applied to study the enantioselective reduction of 3-morpholin-4-yl-1-phenyl-1-propanone with borane catalyzed by (S)-4-benzyl-5,5- diphenyl-1,3,2-oxazaborolidine at the B3LYP/6-31G* level. All molecular species involved in the four reaction steps have been fully optimized and the structural parameters are provided, and the micro process of reaction was also investigated. The catalyst-alkoxyborane adduct formed in step III exhibits a B-O-B-N tetra-atomic ring. Reaction coordination calculations show that BH3 can react with 3-morpholin-4-yl-1-phenyl-1-propanone spontaneously, resulting in the need of 2 mol BH3 in the reaction.展开更多
In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artem...In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.展开更多
Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene mo...Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene molecule CssSn has a nearly planar tetra-coordinated Sn atom on the skeleton of cage, it is a heterofullerene molecule with odd number of atoms and a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/CEP-31G level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface, and its heat of formation was estimated in this study. Owing to the C2 symmetry of [5,6]-heterofullerene-C58Sn-C2, it is a chiral molecule.展开更多
1,2-Benzothiazine derivatives methyl 3-methoxy-4-oxo-3,4-dihydro-2H-benzo[e] [1,2]thiazine-3-carboxylate 1,1-dioxide（1） and methyl 2-ethyl-3-hydroxy-4-oxo-3,4-dihydro-2Hbenzo[e][1,2]thiazine-3-carboxylate 1,1-dioxid...1,2-Benzothiazine derivatives methyl 3-methoxy-4-oxo-3,4-dihydro-2H-benzo[e] [1,2]thiazine-3-carboxylate 1,1-dioxide（1） and methyl 2-ethyl-3-hydroxy-4-oxo-3,4-dihydro-2Hbenzo[e][1,2]thiazine-3-carboxylate 1,1-dioxide（2） were synthesized, and characterized by spectroscopic techniques; 1H-NMR and infrared（IR） spectroscopy. Crystals of 1 and 2 were grown by slow evaporation of methanol and ethyl acetate, respectively and their crystal structures were investigated by single-crystal X-ray diffraction analysis. Geometric properties were calculated by the B3 LYP method of density functional theory（DFT） at the 6-31G＋（d） basis set to compare with the experimental data. Simulated properties were found in strong agreement with the experimental ones. Intermolecular forces have also been modeled in order to investigate the strength of packing and strong hydrogen bonding was observed in both compounds 1 and 2. Electronic properties such as Ionization Potential（IP）, Electron Affinities（EA） and coefficients of the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） of com- pounds 1 and 2 were simulated for the first time.展开更多
Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, res...Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.展开更多
文摘The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and transition states involved in this reaction have been optimized at the （U）B3LYP/6-31＋G（d,p） level, and then their accurate relative energies have been improved using the G3MP2B3 method. The potential energy profile is confirmed via intrinsic reaction coordinate calculations of transition states. Four possible production channels are examined respectively, as H＋ transfer, H-atom transfer, H2＋ transfer, and bi- molecular nucleophilic substitution （SN2） reaction pathways. Based on present calculations, the H2＋ transfer reaction is major among these four channels, which agrees with previous experimental conclusions.
基金This work was supported by the Natural Science Foundation of Shandong Province (Y2002G11)
文摘Using geometry optimization and DFT method at the B3LYP/6-31G* level for C20H10, an equilibrium geometry is identified to have the form of polyhedral hydrocarbon with five carbon-carbon single bonds linking two pentaprismane cages. Thus, C20H10 is a tri-cage molecule with three pentaprismane cages. Vibrational frequencies and infrared spectrum are computed at the same level. The heat of formation for this molecule has also been estimated in this paper.
基金supported by the National Natural Science Foundation of China(No.21102099)
文摘The crystal structure of the title compound, diethyl 4,5-di（thienyl）-3,6-bis（trime- thylsilyl）phthalate （C26H3404S2Si2, Mr = 530.83）, has been determined by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pccn with a = 43.008（5）, b = 10.9000（12）, c = 11.9357（14） A, V= 5595.3（11） A3, Z = 8, F（000） = 2256, Dc= 1.260 mg/m3, p = 0.305 mm-1, T = 113（2） K, S = 1.090, R = 0.0413 and wR = 0.0969 for 5952 observed reflections with 1 〉 2o（/）. The benzene ring system is planar and makes dihedral angles of 63.7（2） and 72.5（4） with the two thienyl rings A （C（23）-C（26）, S（2）） and B （C（19）-C（22）, S（1））, respectively. The UV-vis absorption and fluorescence of the title compound were discussed. The molecular structure of the title compound has been optimized using DFT method at the B3LYP/6-31G（d） level. The computational results showed that the optimized geometer parameters are consistent well with the experiment data. The vertical ionization potential, vertical electron affinity and frontier orbitals were also discussed.
文摘Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 （D6） and C24O have been performed using density functional theory （DFT） method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G（d） level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20574043） and the Natural Science Foundation of Shandong Province （No.Z2007B02）.
文摘The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G（d,p） and G3MP2B3 levels, respectively. Based on the B3LYP/6- 31G（d,p） optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G（d,p） level. Isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and a-complex structure has the highest energy and will not exist.
文摘Theoretical studies on a series of oligobenzothiophenes were carded out with the AM 1 and DFT methods. Based on B3LYP/6-31G（D） optimized geometries, the electronic spectra, IR spectra and NMR spectra of the oligomers were calculated by INDO/CIS, AM1 and B3LYP/6-31G（D） methods, respectively. The energy gaps decrease, and the absorption in elec- tronic spectra exhibits a red-shift as polymerization increases. The IR frequencies are little affected by the polymerization and substituents. The ^13C chemical shifts are changed to be upfield since the electron-donating groups increase the electron density of carbon atoms but remain unchanged with the increase of polymerization.
文摘Theoretical investigation on the highest epoxygenated fullerene C36018 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G（d） level. Their equilibrium structures, thermal stabilities, electronic structures, vertical ionization potentials, vertical electron affinities, vibrational frequencies and 13C NMR chemical shifts have been studied. The calculation results showed that C36O18 isomers have higher LUMO-HOMO energy gaps than the fullerene C36 and should be more stable. Compared with C36, it is less possible for C36O18 to accept or donate electrons from reduced VEAs and enhanced VIPs. It has been found that C36O18 isomers are not aromatic at all or antiaromatic on analyzing the NICS values. The present study will encourage further theoretical and experimental analyses of this system in future.
基金Project supported by the Research Foundation of Suzhou University (Q3109306)
文摘Density functional theory (DFT) has been applied to study the enantioselective reduction of 3-morpholin-4-yl-1-phenyl-1-propanone with borane catalyzed by (S)-4-benzyl-5,5- diphenyl-1,3,2-oxazaborolidine at the B3LYP/6-31G* level. All molecular species involved in the four reaction steps have been fully optimized and the structural parameters are provided, and the micro process of reaction was also investigated. The catalyst-alkoxyborane adduct formed in step III exhibits a B-O-B-N tetra-atomic ring. Reaction coordination calculations show that BH3 can react with 3-morpholin-4-yl-1-phenyl-1-propanone spontaneously, resulting in the need of 2 mol BH3 in the reaction.
文摘In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.
基金supported by the Natural Science Foundation Committee of China (No. 60671010)
文摘Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene molecule CssSn has a nearly planar tetra-coordinated Sn atom on the skeleton of cage, it is a heterofullerene molecule with odd number of atoms and a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/CEP-31G level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface, and its heat of formation was estimated in this study. Owing to the C2 symmetry of [5,6]-heterofullerene-C58Sn-C2, it is a chiral molecule.
基金funded by the Saudi Basic Industries Corporation(SABIC) and the Deanship of Scientific Research(DSR),King Abdulaziz University,Jeddah,under grant no.(MS/15/396/1434)
文摘1,2-Benzothiazine derivatives methyl 3-methoxy-4-oxo-3,4-dihydro-2H-benzo[e] [1,2]thiazine-3-carboxylate 1,1-dioxide（1） and methyl 2-ethyl-3-hydroxy-4-oxo-3,4-dihydro-2Hbenzo[e][1,2]thiazine-3-carboxylate 1,1-dioxide（2） were synthesized, and characterized by spectroscopic techniques; 1H-NMR and infrared（IR） spectroscopy. Crystals of 1 and 2 were grown by slow evaporation of methanol and ethyl acetate, respectively and their crystal structures were investigated by single-crystal X-ray diffraction analysis. Geometric properties were calculated by the B3 LYP method of density functional theory（DFT） at the 6-31G＋（d） basis set to compare with the experimental data. Simulated properties were found in strong agreement with the experimental ones. Intermolecular forces have also been modeled in order to investigate the strength of packing and strong hydrogen bonding was observed in both compounds 1 and 2. Electronic properties such as Ionization Potential（IP）, Electron Affinities（EA） and coefficients of the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） of com- pounds 1 and 2 were simulated for the first time.
基金This work was supported by the Natural Science Foundation of Shandong Province (Y2002G11)
文摘Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.
