Coupling of torsion and OH-stretching in <i>tert</i>-butyl hydroperoxide. II. The OH-stretching fundamental and overtone spectra

Vogt, Emil; Huchmala, Rachel M.; Jensen, Casper V.; Boyer, Mark A.; Wallberg, Jens; Hansen, Anne S.; Kjærsgaard, Alexander; Lester, Marsha I.; McCoy, Anne B.; Kjaergaard, Henrik G.

doi:10.1063/5.0048022

Cited by 14 publications

(22 citation statements)

References 57 publications

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“…In conclusion, the FTIR jet spectra of propargyl alcohol confirm our previous interpretation of the Raman jet spectra as well as the expectation that symmetry-changing transitions do not follow the simple vibrational Franck-Condon scheme (Table S11) but carry nonnegligible IR activity [93,95]. The FTIR jet spectra of propargyl alcohol and α-fenchol at cold conditions are very similar, both featuring one intense band and a higher-wavenumber less-intense band, separated by the torsional splitting of the excited OH stretching state.…”

supporting

confidence: 86%

“…No Raman activity for conceivable symmetry-changing transitions (u 1 ← l 0 and l 1 ← u 0 ) at 3680 or 3640 cm −1 was observed. Analogous transitions for hydroperoxides were shown to have non-negligible infrared activity for multi-quanta OH stretching excitation [93][94][95], contrary to the symmetryselection rules from the simple vibrational Franck-Condon model; for single-quantum OH stretch excitation even intensities comparable with the symmetry-conserving transitions are predicted [93,95]. Considering the structural similarities between alkyl hydroperoxides and alcohols, we extend here our investigation of propargyl alcohol to FTIR detection.…”

mentioning

confidence: 75%

“…Due to known shortcomings of the Franck-Condon model [93][94][95] and the sensitivity on the details of the potential, the latter hypothesis however requires further investigation, especially explicit theoretical modelling of relative IR and Raman intensities. Further experimental insights might come from microwave characterization of the second and perhaps also the third torsional state populated in a milder jet expansion or at ambient temperature, a direct measurement of the mm-wave or THz torsional transitions expected at 16(1) (OH) and 7(1) cm −1 (OD), as well as analysis of OH and OD stretching overtone spectra.…”

Section: Discussionmentioning

confidence: 99%

“…An error in the calculated asymmetry of the potential is likely not to blame for this deviation, as the agreement cannot be substantially improved by varying the asymmetry in a concerted way for the OH stretch ground and excited state (Figure S36). This underestimation of transition intensities connecting torsional wave function with different number of nodes by the Franck-Condon model is reminiscent of the situation for OH stretching spectra of symmetric hydroperoxides [93][94][95] It was explained by a neglected component of the transition dipole moment being an antisymmetric function of the torsional coordinate, which needs to be factored into the symmetry selection rules.…”

Section: Theoretical Investigation Of Torsional States Of α-Fencholmentioning

confidence: 99%

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Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of alpha-Fenchol

Medel¹,

Springborn²,

Crittenden³

et al. 2021

Preprint

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Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second expected torsional conformer, despite computational predictions that it is only very slightly higher in energy than the most stable conformer. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modelling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm$^{−1}hc$ for the protiated and deuterated alcohol, respectively, which further shrink to 9(1) and 3(1) cm$^{−1}hc$ upon OH or OD stretch excitation. Comparisons are made with the more strongly asymmetric monoterpenols borneol and isopinocampheol as well as with the symmetric, rapidly tunneling propargyl alcohol. Assigned are also for α-fenchol the third – in contrast localized – torsional conformer and the most stable dimer, as well as for propargyl alcohol the two most stable dimers.

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supporting

confidence: 86%

mentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Section: Theoretical Investigation Of Torsional States Of α-Fencholmentioning

confidence: 99%

See 2 more Smart Citations

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of alpha-Fenchol

Medel¹,

Springborn²,

Crittenden³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…An error in the calculated asymmetry of the potential is likely not to blame for this deviation, as the agreement cannot be substantially improved by varying the asymmetry in a concerted way for the OH stretch ground and excited state ( Figure S36 ). This underestimation of transition intensities connecting torsional wave function with different number of nodes by the Franck–Condon model is reminiscent of the situation for OH stretching spectra of symmetric hydroperoxides [ 114 , 115 , 116 ]. It was explained by a neglected component of the transition dipole moment being an antisymmetric function of the torsional coordinate, which needs to be factored into the symmetry selection rules.…”

Section: Resultsmentioning

confidence: 99%

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

et al. 2021

View full text Add to dashboard Cite

Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second most stable torsional conformer, despite computational predictions that it is only very slightly higher in energy than the global minimum. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modeling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm−1hc for the protiated and deuterated alcohol, respectively, which further shrink to 9(1) and 3(1) cm−1hc upon OH or OD stretch excitation. Comparisons are made with the more strongly asymmetric monoterpenols borneol and isopinocampheol as well as with the symmetric, rapidly tunneling propargyl alcohol. In addition, the third—in contrast localized—torsional conformer and the most stable dimer are assigned for α-fenchol, as well as the two most stable dimers for propargyl alcohol.

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Exploring the Origins of Spectral Signatures of Strong Hydrogen Bonding in Protonated Water Clusters

Huchmala

McCoy

2022

J. Phys. Chem. A

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The effects of anharmonicity on the spectral features of strong ionic hydrogen bonds are explored through reduced dimensional studies of the couplings between the hydrogen bonding OH and the donor–acceptor OO stretching vibrations in protonated water clusters with 2–4 water molecules. Specifically, this study focuses on how the anharmonicities and couplings in these ions are reflected in the vibrational spectra by exploring the intensities of the transitions to states with excitation in both the OH and the OO stretching vibrations and changes in the frequency of the OO stretching vibration when the OH stretching vibration is excited. These questions are addressed through the application of several approximate treatments that are based on an adiabatic separation of the high-frequency OH and low-frequency OO stretching vibrations as well as low-order expansions of the potential and dipole surfaces. While an adiabatic approximation captures most of the trends found in the spectra and from an analysis of the two-dimensional model, a vibrational Franck–Condon approach fails to capture the intensities of these transitions. Of the terms in the expansion of the dipole moment function, those that are proportional to Δr OH and Δr OH 2 are found to provide the largest contributions to the calculated intensities of the transitions involving excitation of both the OH and the OO stretches. This leads to the conclusion that the intensities of these transitions encode information about the frequency and anharmonicity of the OH stretching vibration and how they are affected by changes in the OO distance. The anharmonicity of the potential also leads to changes in the OO stretching frequency with excitation of the OH stretching vibration. The direction of this change in frequency encodes additional information about the strength of the ionic hydrogen bond.

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Coupling of torsion and OH-stretching in tert-butyl hydroperoxide. II. The OH-stretching fundamental and overtone spectra

Cited by 14 publications

References 57 publications

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of alpha-Fenchol

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of alpha-Fenchol

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

Exploring the Origins of Spectral Signatures of Strong Hydrogen Bonding in Protonated Water Clusters

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