The equilibrium structure of thiophene by the combined use of electron diffraction, vibrational spectroscopy and microwave spectroscopy guided by theoretical calculations

Кочиков, И. В.; Tarasov, Yu. I.; Spiridonov, V. P.; Kuramshina, G. M.; Rankin, David W. H.; Saakjan, A.S.; Yagola, A. G.

doi:10.1016/s0022-2860(01)00539-7

Cited by 47 publications

(26 citation statements)

References 20 publications

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“…suggested in [15] without any justification is, of course, absolutely incorrect. Conversely, in [16][17][18], the equation given above was used.…”

Section: Scaling Of Cubic Force Constantsmentioning

confidence: 99%

“…"Centrifugal" Problem: Equation (15) This problem ("bond-on-a-block problem") was casually discussed by Bartell [8]. It involves the derivatives of the kinetic energy with respect to coordinates.…”

Section: Equation Of Motionmentioning

confidence: 99%

“…In this system, the eigenvectors of the vibrational problem of the first approximation are "unit" vectors. Let us stage-by-stage reproduce solution to problem (15):…”

Section: Equation Of Motionmentioning

confidence: 99%

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Diffraction Measurements and Equilibrium Parameters

Sipachev

2011

Advances in Physical Chemistry

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Structural studies are largely performed without taking into account vibrational effects or with incorrectly taking them into account. The paper presents a first-order perturbation theory analysis of the problem. It is shown that vibrational effects introduce errors on the order of 0.02Å or larger (sometimes, up to 0.1-0.2Å) into the results of diffraction measurements. Methods for calculating the mean rotational constants, mean-square vibrational amplitudes, vibrational corrections to internuclear distances, and asymmetry parameters are described. Problems related to low-frequency motions, including torsional motions that transform into free rotation at low excitation levels, are discussed. The algorithms described are implemented in the program available from the author (free).

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“…suggested in [15] without any justification is, of course, absolutely incorrect. Conversely, in [16][17][18], the equation given above was used.…”

Section: Scaling Of Cubic Force Constantsmentioning

confidence: 99%

Section: Equation Of Motionmentioning

confidence: 99%

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Diffraction Measurements and Equilibrium Parameters

Sipachev

2011

Advances in Physical Chemistry

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“…Spectrochemical methods, including vibrational spectroscopy, dominate in constructing structural dynamic models for such compounds. So reliable interpretation of the vibrational states of the individual fragments of the molecular system is needed.To date, extensive experimental data has been accumulated on the vibrational spectra of pyrrole, furan, thiophene, selenophene, and a number of their substituted derivatives [1][2][3][4][5][6][7][8][9][10]. Theoretical analysis of the vibrational spectra of pyrrole, furan, and thiophene has often been carried out in the harmonic approximation of the theory of molecular vibrations [1,2].…”

mentioning

confidence: 99%

“…The anharmonic shift of the fundamental vibrational states in the studied molecules can be described by the scaling relation ν m = -8.35⋅10 −6 ν h 2 + 0.9813ν h [17]. 6. Delocalization of the normal vibrational mode occurs for in-plane stretching and bending vibrations of the five-membered ring (vibrations of symmetry type A 1 and B 2 ).…”

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confidence: 99%

Anharmonic analysis of vibrational states for five-membered heterocyclic compounds

2007

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We have used the DFT/B3LYP method with 6-31G * ( ** ) basis sets for analysis of the vibrational spectra and geometric structure of pyrrole, furan, thiophene, and selenophene in the anharmonic approximation. We have determined the influence of resonance effects on the nature of the vibrational states.Key words: calculation of anharmonic vibrational spectra of pyrrole, furan, thiophene; structural dynamic model; anharmonic constants; Fermi resonance; intensities of IR and Raman spectra.Introduction. Five-membered heterocyclic molecules are fragments of complex molecular systems having important practical value. Spectrochemical methods, including vibrational spectroscopy, dominate in constructing structural dynamic models for such compounds. So reliable interpretation of the vibrational states of the individual fragments of the molecular system is needed.To date, extensive experimental data has been accumulated on the vibrational spectra of pyrrole, furan, thiophene, selenophene, and a number of their substituted derivatives [1][2][3][4][5][6][7][8][9][10]. Theoretical analysis of the vibrational spectra of pyrrole, furan, and thiophene has often been carried out in the harmonic approximation of the theory of molecular vibrations [1,2]. Nevertheless, there is no established interpretation of the fundamental vibrational frequencies due to the limited possibilities of the classical approach [1] for determining the quadratic force constants of the molecules, associated with solution of inverse spectral problems.Selection of the zero-th approximation for the original force field for the five-membered ring C 1 C 2 X 3 C 4 C 5 (X = N, O, S, Se), based on transfer of quadratic force constants or influence factors [1] from cyclic compounds containing similar valence bonds and bond angles, led to ambiguities in the solutions of the inverse problems. To our knowledge, no such theoretical analysis of the vibrational spectra has been carried out for selenophene.Anharmonic analysis of the vibrational states of the considered molecules has been carried out occasionally, and has clearly been limited in connection with the lack of reliable software packages permitting such calculations to be performed. The possibility of anharmonic analysis of the vibrational states of polyatomic molecules became realistic when the Gaussian-2003 package appeared [10].When using direct ab initio quantum calculations of the geometry, electronic structure, and vibrational spectra, there is always the problem of choosing the calculation method and the basis. Analysis of the vibrational states of fivemembered heterocyclic molecules in the harmonic approximation of the theory of vibrations, presented in monograph [2], showed that for this class of compounds, preference should be given to the DFT/B3LYP/6-31 G * method [2].The aim of this work was analysis of the anharmonic properties of the adiabatic potential and the vibrational states of pyrrole, furan, thiophene, and selenophene.Structural Dynamic Models. In constructing structural dynamic models for ...

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Equilibrium Molecular Structure as Determined by Gas-Phase Electron Diffraction

Vogt,

Demaison

2023

Lecture Notes in Chemistry

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The equilibrium structure of thiophene by the combined use of electron diffraction, vibrational spectroscopy and microwave spectroscopy guided by theoretical calculations

Cited by 47 publications

References 20 publications

Diffraction Measurements and Equilibrium Parameters

Diffraction Measurements and Equilibrium Parameters

Anharmonic analysis of vibrational states for five-membered heterocyclic compounds

Equilibrium Molecular Structure as Determined by Gas-Phase Electron Diffraction

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