排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
The structure of the conformationally flexible 2-fluoroethanal molecule (CH2FCHO, FE) in the ground (S0) and lowest excited triplet (T1) and singlet (S1) electronic states was investigated by ab initio quantum-chemical methods. The FE molecule in the S0 state was found to exist as two conformers, viz., as cis (the F—C—C—O angle is 0°) and trans (the F—C—C—O angle is 180°) conformers. On going both to the T1 and S1 states, the FE molecule undergoes substantial structural changes, in particular, the CH2F top is rotated with respect to the core and the carbonyl CCHO fragment becomes nonplanar. The potential energy surfaces for the T1 and S1 states are qualitatively similar, viz., six minima in each of the excited states of FE correspond to three pairs of mirror-symmetrical conformers. Based on the potential energy surfaces calculated for the FE molecule in the T1 and S1 states, the one-dimensional problems on the torsion and inversion nuclear motions as well as the two-dimensional torsion-inversion problems were solved. 相似文献
2.
3.
V. A. Bataev E. K. Dolgov A. V. Abramenkov G. M. Kuramshina I. A. Godunov 《Russian Chemical Bulletin》2000,49(6):984-990
The molecular structure of 2,2-difluoroethanal (DFE) in the ground (S0) and lowest excited triplet (Ti) electronic states was investigated byab initio quantum-chemical methods. In the S0 state, the DFE molecule exists as the only stablecis conformer. The Ti↓S0 electronic excitation is accompanied by the rotation of the top and the deviation of the carbonyl fragment from planarity.
For the DFE molecule in the Ti state, six minima corresponding to three pairs of enantiomers were found on the potential energy surface. Based on this potential
energy surface, the problems on torsion and inversion nuclear motions were solved in the one- and two-dimensional approximations,
and the interaction between these motions was revealed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 989–995, June, 2000. 相似文献
4.
5.
V. A. Bataev M. N. Mikhailov A. V. Abramenkov V. I. Pupyshev I. A. Godunov 《Journal of Structural Chemistry》2001,42(1):57-65
This paper reports on an ab initio quantum mechanical calculation of the structure of the conformationally nonrigid chloral (CCl3CHO) molecule in the ground (S0) and lowest excited triplet (T1) states. Electronic excitation causes substantial changes in molecular geometry: the CCl3 top is rotated, and the carbonyl (CCHO) fragment becomes nonplanar. For the torsional (S0 and T1) and inversion (T1) nuclear vibrations, one- (S0 and T1) and two-dimensional (T1) vibrational problems are solved; a relationship is found between the torsional and inversion vibrations in the T1 state. The results are compared with the data of analogous calculations for the acetaldehyde molecule in the T1 state. 相似文献
6.
Ekaterina V. Rastoltseva Vadim A. Bataev Alexander V. Abramenkov Vladimir I. Pupyshev Igor A. Godunov 《Journal of Molecular Structure》2010,939(1-3):14-21
Geometric parameters, harmonic and anharmonic vibrational frequencies, conformer energy differences and barriers to internal rotation were obtained for dicyclopropyl ketone (DCPK) in the ground electronic state through MP2, DFT, CCSD and CCSD(T) calculations. VFPA was used to improve the estimations of conformer energy differences and heights of barriers to internal rotation. The ab initio calculations demonstrated that there are three stable conformations of DCPK: the cis–cis, the cis–trans and the gauche–gauche. The energy of the gauche–gauche conformer is noticeably higher than the energy of the two other conformers, so this conformer was not found experimentally. To study the conformational dynamics of the DCPK molecule, one- and two-dimensional sections of the potential energy surface corresponding to the rotations of the cyclopropyl groups were calculated. These sections were used to calculate torsion transition energies and vibrational wave functions in anharmonic approach. It was found that there is a strong coupling of large-amplitude torsion motions in the area of the cis–cis and gauche–gauche conformers. 相似文献
7.
Vadim A. Bataev Eugeniy K. Dolgov Alexandr V. Abramenkov Vladimir I. Pupyshev Igor A. Godunov 《International journal of quantum chemistry》2002,88(4):414-425
The potential energy surface (PES) for the CHF2CHO molecule in the excited S1 state is calculated by the CASSCF method. The features of the 1‐ and 2‐D cross‐sections of PES are considered in comparison with those of the relative molecules. The vibrational frequencies are calculated in harmonic approximation and the vibrational energy levels for the inversion motion of the carbonyl fragment CCHaO and for the torsion motion of the CHF2‐top are calculated in anharmonic approximation by the 1‐ and 2‐D variational methods. The calculated data are compared with the experimental ones. The problems of the experimental data interpretation are considered. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
8.
Sergey I. Bokarev Evgeny K. Dolgov Vadim A. Bataev Igor A. Godunov 《International journal of quantum chemistry》2009,109(3):569-585
Geometrical parameters of tetraatomic carbonyl molecules X2CO and XYCO (X, Y = H, F, Cl) in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states as well as values of barriers to inversion in S1 and T1 states and S1 ← S0 and T1 ← S0 adiabatic transition energies were systematically investigated by means of various quantum‐chemical techniques. The following methods were tested: HF, MP2, CIS, CISD, CCSD, EOM‐CCSD, CCSD(T), CR‐EOM‐CCSD(T), CASSCF, MR‐MP2, CASPT2, CASPT3, NEVPT2, MR‐CISD, and MR‐AQCC within cc‐pVTZ and cc‐pVQZ basis sets. The accuracy of quantum‐chemical methods was estimated in comparison with experimental data and rather accurate structures of excited electronic states were obtained. MP2 and CASPT2 methods appeared to be the most efficient and CCSD(T), CR‐EOM‐CCSD(T), and MR‐AQCC the most accurate. It was found that at equilibrium all the molecules under study are nonplanar in S1 and T1 electronic states with CO out‐of‐plane angle ranging from 34° (H2CO, S1) to 52° (F2CO, T1), and height of barrier to inversion varying from 300 (H2CO, S1) to 11,000 (F2CO, T1) cm?1. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
9.
V. A. Bataev A. V. Kudich A. V. Abramenkov I. A. Godunov 《Journal of Structural Chemistry》2001,42(1):66-75
Ab initio calculations were carried out to investigate the molecular structure of 2,2-dichloroethanal (DCE, CHCl2CHO) in the ground (S
0) and excited lowest triplet (1) states. It is found that electronic excitation of DCE from the S
0 to T
1 state occurs with top rotations and a loss of planarity of the carbonyl fragments. Six minima corresponding to three pairs of enantiomers were found on the potential energy surface (PES) of the DCE molecule in the 1 state. Based on the PES calculated (by the UHF and CASSCF methods in a 6-31G** basis) for DCE in the 1 state, the one-dimensional torsional and inversion problems and the two-dimensional torsional-inversion problems are solved. A comparison of the results has revealed a relationship between the torsional and inversion motions. 相似文献
10.
I. A. Godunov A. V. Abramenkov V. A. Bataev V. I. Pupyshev 《Russian Chemical Bulletin》1999,48(4):640-646
The inversion potentials of R2CO (R=H, F, Cl) molecules in the lowest excited electronic states were determined from experimental data using various model
potential functions and approximations for the kinetic energy operator of inversion motion. The estimates of the heights of
the barriers to inversion and the equilibrium values of the inversion coordinate for the H2CO molecule in the S1 and T1 states are fairly stable. The results for the F2CO and Cl2CO molecules are strongly dependent on the approximation used; for these molecules, the most reliable parameters of the potential
functions were chosen. The problem of qualitative characteristics of the shape of inversion potentials is discussed using
the results ofab initio quantum-chemical calculations of the molecules under study.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 645–651, April, 1999. 相似文献