Vibrational spectroscopy of protonated amine–water clusters: tuning Fermi resonance and lighting up dark states

Lin, Chu-Sheng; Shishido, Ryunosuke; Huang, Qian‐Rui; Fujii, Asuka; Kuo, Jer‐Lai

doi:10.1039/d0cp03229h

Cited by 18 publications

(23 citation statements)

References 50 publications

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“…At lower wavenumber, OH stretching resonances are much more abundant, such as in the metastable dimer of formic acid and more prominently in the most stable cyclic dimer of carboxylic acids. , This is a consequence of the stronger coupling which is associated with the lower OH stretching wavenumber in acid complexes. Also, proton-bound complexes usually exhibit strong Fermi resonances, with a most systematic pattern for the NH stretch having been published very recently . It is the unusually small downshift and thus intrinsically weak coupling of the OH stretching oscillator to its environment in ketone solvation which makes the present observation so special because it marks the early onset of systematic rapid OH-vibrational energy distribution as a function of increasing hydrogen bond strength in aqueous solution.…”

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confidence: 64%

“…In summary, we have used a chemical approach to identify and tune an anharmonic resonance, complementing the traditional isotope, pressure, or solvent variation strategies . This systematic chemical tuning approach, in combination with scaled harmonic and anharmonic modeling, brings qualitative and to some extent even quantitative understanding of the onset of intermolecule vibrational energy relaxation as a function of interaction strength.…”

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confidence: 99%

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A Rather Universal Vibrational Resonance in 1:1 Hydrates of Carbonyl Compounds

Fischer

Wagner

Gottschalk

et al. 2020

J. Phys. Chem. Lett.

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When the lower frequency OH stretching fundamental of a water molecule is shifted to the 3500 cm −1 spectral range by the solvation of a carbonyl compound, in this case a ketone, its infrared intensity is shared with a dark state. It is shown by chemical and isotope substitution for more than a dozen systems that the location of this resonance is remarkably substitution-independent. Harmonic and anharmonic model calculations support its assignment to a combination of the water bending overtone and in-plane water libration. This previously unrecognized intramolecular−intermolecular coupling in single solvent water has a strength of 7−10 cm −1 . It may have been sporadically observed before in a few other carbonyl compounds such as amides, without any previous exploration of its potential universality. The resulting generic picosecond energy redistribution channel for aqueous solutions may represent a slow counterpart and doorway model of what happens on a subpicosecond time scale when the hydrogen bonds become stronger, such as in carboxylic acid dimers or protonated water clusters.

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confidence: 64%

mentioning

confidence: 99%

A Rather Universal Vibrational Resonance in 1:1 Hydrates of Carbonyl Compounds

Fischer

Wagner

Gottschalk

et al. 2020

J. Phys. Chem. Lett.

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“…The most stable isomer is the proton bound structure, denoted as N··H + ··N, in which H + is shared by the N atoms of two pyridines. , It should be noted that the energies of the other isomers at the right panel are relative to the N··H + ··N isomer. Similar proton bound structures have been studied by IR spectroscopy for the protonated amine dimer, , protonated water clusters, and protonated ethers . The N–H stretching vibrations in the species containing the N··H + ··N moiety typically appear below 2000 cm –1 , which is not covered by our apparatus.…”

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confidence: 99%

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C–N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry

Feng

Lee

Witek

et al. 2021

J. Phys. Chem. Lett.

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The structures and reactions of pyridine (Pyd) cluster cations in a supersonic molecular beam generated upon photoionization at 9.2–9.4 eV were investigated by infrared (IR) action spectroscopy. The mass spectrum showed prominent peaks of (Pyd) m + and H+(Pyd) m , m = 1–5. In the pyridine/pyridine-d 5 mixture, the mass pattern indicated that H+ and D+ migrated during the formation and dissociation of the cluster cations. The IR photodissociation spectra of both (Pyd)2 + and H+(Pyd)2 revealed a N–H stretching band near 3400 cm–1, indicating that their structures are 1-(2-pyridyl)pyridin-1-ium and pyridinium–pyridine, respectively. Observation of the former product implies that the reaction proceeds via an α-distonic cation intermediate, while the latter product is formed via proton migration. The IR spectra of (Pyd) m + and H+(Pyd) m , m ≥ 3, suggested that these clusters consist of a covalently bound (Pyd)2 + or H+(Pyd)2 core, respectively, with additional pyridines attached to them via hydrogen bonds and/or weak dispersive interactions.

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“…The thermodynamic aspect can be explained on the grounds that the proton affinity (PA) of Asn (~940 kJ⋅mol −1 ) is higher than Val (~910 kJ⋅mol −1 ) and Ser (~920 kJ⋅mol −1 ) [ 69 , 70 ]. In terms of the kinetic aspect of the proton migration, since the fragmentation process is highly energetic [ 71 ], the proton may become loosely bonded between the two monomer subunits, largely free to migrate from one subunit to another. One can draw some comparison to proton mobility effects previously observed by Hopkins et al in dimers of 3-cyanophenylalanine and trimethylamine, where irradiation of different vibrational bands in the fingerprint region led to different proton transfer patterns between the two dissociating fragments [ 72 ].…”

Section: Resultsmentioning

confidence: 99%

Vibrational Spectroscopy of Homo- and Heterochiral Amino Acid Dimers: Conformational Landscapes

et al. 2021

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The homo- and heterochiral protonated dimers of asparagine with serine and with valine were investigated using infrared multiple-photon dissociation (IRMPD) spectroscopy. Extensive quantum-chemical calculations were used in a three-tiered strategy to screen the conformational spaces of all four dimer species. The resulting binary structures were further grouped into five different types based on their intermolecular binding topologies and subunit configurations. For each dimer species, there are eight to fourteen final conformational geometries within a 10 kJ mol−1 window of the global minimum structure for each species. The comparison between the experimental IRMPD spectra and the simulated harmonic IR features allowed us to clearly identify the types of structures responsible for the observation. The monomeric subunits of the observed homo- and heterochiral dimers are compared to the corresponding protonated/neutral amino acid monomers observed experimentally in previous IRMDP/rotational spectroscopic studies. Possible chirality and kinetic influences on the experimental IRMPD spectra are discussed.

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Vibrational spectroscopy of protonated amine–water clusters: tuning Fermi resonance and lighting up dark states

Abstract: Strong coupling between stretching fundamentals and bending overtones of vibrational modes, known as Fermi resonance (FR), has been observed for proton motions in the protonated trimethylamine–water cluster. To investigate the...

Cited by 18 publications

References 50 publications

A Rather Universal Vibrational Resonance in 1:1 Hydrates of Carbonyl Compounds

A Rather Universal Vibrational Resonance in 1:1 Hydrates of Carbonyl Compounds

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C–N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry

Vibrational Spectroscopy of Homo- and Heterochiral Amino Acid Dimers: Conformational Landscapes

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