Trapping of Unstable Conformations from Thermal Molecular‐Beams in Argonmatrices

Huber-Wälchli, P.

doi:10.1002/bbpc.19780820108

Cited by 29 publications

(2 citation statements)

References 8 publications

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“…For assignments for the gauche conformer in this complex spectral region, we focus on the gas-phase RS spectrum, where bands from the gauche species grow in intensity in going from 25 to 250 °C. Counterparts of some of these gas-phase features were observed in matrix-isolation Raman spectra and IR spectra. − The gauche conformer is represented in the A symmetry block by three C–H fundamentals, ν 1 , ν 2 , and ν 3 . The first one (ν 1 ) is FR free and has a predicted frequency of 3096.8 cm –1 and a Raman intensity of 23 RSU.…”

Section: Results and Discussionmentioning

confidence: 99%

“…An enhanced content of the gauche conformer present at high temperature was secured in the quick-freezing process. An early report of an IR investigation was in a note by Squillacote et al Following a note, Huber-Wälchli and Günthard provided a full report of a similar study . Additional IR matrix-isolation studies were by Furukawa et al and Arnold et al, followed by a matrix-isolation RS study by Choi et al Furukawa et al also did an RS study …”

Section: Introductionmentioning

confidence: 99%

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Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

et al. 2015

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A quantum-mechanical (hybrid MP2/cc-pVTZ and CCSD(T)/cc-pVTZ) full quartic potential energy surface (PES) in rectilinear normal coordinates and the second-order operator canonical Van Vleck perturbation theory (CVPT2) are employed to predict the anharmonic vibrational spectra of s-trans- and s-gauche-butadiene (BDE). These predictions are used to interpret their infrared and Raman scattering spectra. New high-temperature Raman spectra in the gas phase are presented in support of assignments for the gauche conformer. The CVPT2 solution is based on a PES and electro-optical properties (EOP; dipole moment and polarizability) expanded in Taylor series. Higher terms than those routinely available from Gaussian09 software were calculated by numerical differentiation of quadratic force fields and EOP using the MP2/cc-pVTZ model. The integer coefficients of the polyad quantum numbers were derived for both conformers of BDE. Replacement of harmonic frequencies by their counterparts from the CCSD(T)/cc-pVTZ model significantly improved the agreement with experimental data for s-trans-BDE (root-mean-square deviation ≈ 5.5 cm(-1)). The accuracy in predicting the rather well-studied spectrum of fundamentals of s-trans-BDE assures good predictions of the spectrum of s-gauche-BDE. A nearly complete assignment of fundamentals was obtained for the gauche conformer. Many nonfundamental transitions of the BDE conformers were interpreted as well. The predictions of multiple Fermi resonances in the complex CH-stretching region correlate well with experiment. It is shown that solving a vibrational anharmonic problem through a numerical-analytic implementation of CVPT2 is a straightforward and computationally advantageous approach for medium-size molecules in comparison with the standard second-order vibrational perturbation theory (VPT2) based on analytic expressions.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

et al. 2015

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Ultraviolet/Visible, Infrared and Raman Spectra

Furukawa

2009

Patai's Chemistry of Functional Groups

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Conformers of Saturated Chains: Matrix Isolation, Structure, IR and UV Spectra of n‐Si₄Me₁₀

Albinsson

Teramae

Downing

et al. 1996

Chemistry A European J

123

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Infrared and ultraviolet spectra of the gauche and anti conformers of matrix-isolated permethyl-n-tetrasilane have been obtained separately by taking advantage of thermally induced gauche-to-anti conversion and of wavelength-selective photochemical destruction of either conformer. The resolved UV spectrum of the gauche conformer provides the first piece of experimental evidence in favor of the recently proposed reinterpretation of conformational effects on tetrasilane electronic states. According to this, it is not the energy but the intensity of the lowest singlet excitation that changes dramatically as the SiSiSiSi dihedral angle is varied, as a result of an avoided crossing between s̀s̀* and s̀π* states. Implications for the general understanding of sigma conjugation in simple terms are discussed. Unconstrained MP2/6-31 G* optimization predicts the existence of a third backbone conformer (ortho), with a dihedral angle of about 90°. Its predicted (HF/3-21 G*) mid-IR spectrum is indistinguishable from that of the gauche conformer, and the matrix-isolation spectra thus provide no evidence for or against its presence.

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Trapping of Unstable Conformations from Thermal Molecular‐Beams in Argonmatrices

Cited by 29 publications

References 8 publications

Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

Ultraviolet/Visible, Infrared and Raman Spectra

Conformers of Saturated Chains: Matrix Isolation, Structure, IR and UV Spectra of n‐Si₄Me₁₀

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Trapping of Unstable Conformations from Thermal Molecular‐Beams in Argonmatrices

Cited by 29 publications

References 8 publications

Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

Anharmonic Vibrational Analysis of the Infrared and Raman Gas-Phase Spectra of s-trans- and s-gauche-1,3-Butadiene

Ultraviolet/Visible, Infrared and Raman Spectra

Conformers of Saturated Chains: Matrix Isolation, Structure, IR and UV Spectra of n‐Si4Me10

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Conformers of Saturated Chains: Matrix Isolation, Structure, IR and UV Spectra of n‐Si₄Me₁₀