1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Towards a first-principles model of Fermi resonance in the alkyl CH stretch region: Application to 1,2-diphenylethane and 2,2,2-paracyclophane
Rent:
Rent this article for
USD
10.1063/1.4790163
/content/aip/journal/jcp/138/6/10.1063/1.4790163
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/6/10.1063/1.4790163

Figures

Image of FIG. 1.
FIG. 1.

Chemical structures of 1,2-diphenylethane (DPE) and 2,2,2-paracyclophane (TCP).

Image of FIG. 2.
FIG. 2.

(a) Two conformers of DPE optimized at the ωB97Xd level of theory with a 6-311+g(d,p) basis set. The anti conformer has C 2h symmetry in which the phenyl groups lie in planes parallel to one another. The gauche conformer has C 2 symmetry. (b) The two conformers of TCP optimized at the same level of theory, differing in the geometry of the ethano bridge. The C 2 conformer is observed experimentally. A side view of the C 2 symmetric conformer is shown omitting one phenyl ring to clarify the up (u)/down (d) designation of the ethano bridge carbons relative to the rings.

Image of FIG. 3.
FIG. 3.

Resonant two-photon ionization spectrum of the two conformations present in the supersonic jet expansion of DPE (a) and the single conformation of TCP (b).

Image of FIG. 4.
FIG. 4.

Dispersed fluorescence spectra of the S 1 origins of the gauche (a) and anti (b) isomers of DPE, and (c) the C 2 symmetry conformer of TCP. The low frequency and ring mode transitions used to assign the conformations are labeled.

Image of FIG. 5.
FIG. 5.

Bend and stretch coordinates included in the anharmonic calculations.

Image of FIG. 6.
FIG. 6.

Comparison of stretch/scissor energetics and couplings for anti-DPE and gauche-DPE. The width of the CH stretch states is proportional to the oscillator strength, and the vertical center of the box corresponds to the transition energies associated with the states of Eq. (10) . For the gauche conformer, these energies are 2909, 2906, 2942, and 2934 cm−1. The width of the lines connecting CH stretches to scissor overtones and combinations is proportional to the associated couplings.

Image of FIG. 7.
FIG. 7.

Comparison of the experimental (upper line) and theoretical spectra for (a) anti-DPE, (b) gauche-DPE, and (c) TCP. In each panel, the top curve is experimental result. In (c) the C 2 symmetry TCP conformer result is shown in red, while that for the C 3 conformer is shown in blue. (d) shows the ud (middle) and du (lower) contributions to the TCP C 2 conformer spectrum. Note the close similarity between the ud result and the spectrum obtained for conformer C 3. Scaling factors for the B3LYP/6-311+(d,p) calculations are αCH = 0.9595, α FC = 0.68, β = .85, and E anh = −47 cm−1. The theoretical spectra are calculated assuming Gaussian lineshapes, where the width is chosen to match approximately the widths of the experimental lines.

Image of FIG. 8.
FIG. 8.

Comparison of the experimental (upper line) and theoretical spectra for TCP. The C 2 symmetry conformer result is shown in red, while that for the C 3 conformer is shown in blue. This figure is the same as Fig. 7(c) , but here Fermi coupling is set to zero.

Image of FIG. 9.
FIG. 9.

Normal mode motions for select modes of CH2D2. Green atoms are hydrogens and blue atoms are deuteriums. The frequencies (in cm−1) of modes {ω4, ω5, ω8, ω9} are {1361, 1470, 3126, 3126}.

Tables

Generic image for table
Table I.

Calculated harmonic frequencies (cm−1) and symmetries for select modes of the two lowest energy conformations of DPE and TCP.

Generic image for table
Table II.

Coordinate definitions for the stretches R ij , bends θ ijk , and dihedral angles ϕ ijkl based on numbering scheme of Fig. 5 .

Generic image for table
Table III.

Comparison of eigenvalues (cm−1) and intensities (KM/mol) of 1-2 difluoroethane in the gauche configuration for the local mode Hamiltonian, the dressed local mode Hamiltonian, and normal mode Hamiltonian H HO obtained using the GAUSSIAN09 package. 52

Loading

Article metrics loading...

/content/aip/journal/jcp/138/6/10.1063/1.4790163
2013-02-14
2014-04-18
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Towards a first-principles model of Fermi resonance in the alkyl CH stretch region: Application to 1,2-diphenylethane and 2,2,2-paracyclophane
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/6/10.1063/1.4790163
10.1063/1.4790163
SEARCH_EXPAND_ITEM