Infrared spectra of weak H-bonds: beyond an adiabatic description of Fermi resonances

Chamma, Didier; Henri‐Rousseau, Olivier

doi:10.1016/s0301-0104(99)00228-1

Cited by 76 publications

(62 citation statements)

References 15 publications

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“…[22] However, such an assignment is not supported by the observed intensity changes under temperature variation and dilution, and a more reasonable explanation is proposed herein by assuming the presence of a CÀH···O dimerization equilibrium. Alternative explanations for the nC=O band splitting, such as keto-enol equilibrium or Davydov coupling [23] have also been considered and discarded.…”

Section: Vibrational Spectroscopymentioning

confidence: 99%

CH⋅⋅⋅O Hydrogen Bonds in Cyclohexenone Reveal the Spectroscopic Behavior of CH and CH Donors

Nolasco

Ribeiro‐Claro

2005

ChemPhysChem

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C-H...O hydrogen bonds in liquid 2-cyclohexen-1-one are studied to assess the vibrational spectroscopic behavior of the Csp2-H and Csp3-H donors. The presence of a pseudo-isosbestic point in the vC = O region supports the assignment of the two observed bands to two species in equilibrium, considered to be the free and 1:1 associated forms. The values of deltaH degrees =-18.5 +/- 0.6 kJmol(-1) and deltaS degrees = -76 +/- 2 J K(-1) mol(-1) for the dimerization through C-H...O hydrogen bonds were obtained from the dimerization constant at different temperatures. The concentration-dependent intensity of the vCH2 band profile is ascribed to the presence of a blue-shifted band from the hydrogen-bonded Csp3-H group. However, the most surprising result is the absence of concentration- or temperature-dependent intensities in the bands assigned to the stretching modes of the Csp2-H donors.

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Section: Vibrational Spectroscopymentioning

confidence: 99%

CH⋅⋅⋅O Hydrogen Bonds in Cyclohexenone Reveal the Spectroscopic Behavior of CH and CH Donors

Nolasco

Ribeiro‐Claro

2005

ChemPhysChem

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“…The red-shift has been used to characterize the strength of hydrogen bonds [10]. Spectral broadening can arise from a number of mechanisms, among them anharmonic coupling to low-frequency modes, Fermi resonances with overtone and combination tone levels of fingerprint modes, vibrational dephasing, and inhomogeneous broadening due to different hydrogen bonding geometries in the molecular ensemble [11][12][13][14][15].…”

Section: Vibrational Excitations Of Hydrogen Bonded Systemsmentioning

confidence: 99%

“…Considering both anharmonic and excitonic coupling, the coupled system has been described by taking into account the C 2 symmetry of the cyclic dimer and introducing symmetrized vibrational coordinates q g,u = (1/ ffiffi ffi 2 p )(q 1 -q 2 ) and Q i,g,u = (1/ ffiffi ffi 2 p )(Q i,1 -Q i,2 ) (i = 1,2,..) for the stretching and the low-frequency modes i, respectively. Taking into account this symmetry and evaluating the dipole selection rules, one finds that transitions between |v u (q u )> states are infrared active whereas transitions between |v g (q g )> states contribute to the Raman band of the O-H stretching mode (v u,g : vibrational quantum numbers) [12,14,15]. The v u = 1 potential energy surface along the gerade Q i,g coordinate remains unaltered whereas the excitonic coupling V 0 leads to a splitting of the v u = 1 potential energy surface along the ungerade Q i,u coordinate by 2V 0 .…”

Section: Vibrational Excitations Of Hydrogen Bonded Systemsmentioning

confidence: 99%

Coherent Low‐frequency Motions in Condensed Phase Hydrogen Bonding and Transfer

Elsaesser

2006

Hydrogen‐Transfer Reactions

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Hydrogen bonding represents a local interaction which determines the fluctuating structure of liquids forming extended molecular networks, e.g., water and alcohols, as well as macromolecular structure of biological relevance. Hydrogen bonds also play a key role in hydrogen and proton transfer processes in both electronic ground and excited states [1,2]. The structural dynamics of hydrogen bonds and proton transfer processes are determined by motions along nuclear coordinates which are characterized by vibrational periods in the femtosecond time domain. For instance, the period of an O-H stretching vibration is of the order of 10 fs whereas low-frequency modes of hydrogen bonds display periods of up to several hundred femtoseconds. In general, vibrational modes of hydrogen bonds show pronounced coupling to each other, resulting in a highly complex dynamics of structural changes.The dynamics of hydrogen bonded systems cover a wide range in time, from about 50 fs up to tens of picoseconds [2]. Linear vibrational spectroscopy, a standard tool of hydrogen bond research, provides the steady-state, i.e., time-averaged infrared and Raman spectra, giving very limited insight into the processes underlying such dynamics. In most cases, there is no quantitative understanding of vibrational line shapes and the different broadening mechanisms, in spite of extensive theoretical work on molecular potential energy surfaces and vibrational couplings. Much more infomation is available from studies of the nonlinear vibrational response in which the macroscopic vibrational polarization and/or changes in vibrational absorption display a higher order dependence on the amplitude of the radiation fields interacting with the sample. Nonlinear vibrational spectroscopy in the femtosecond time domain allows one to observe ultrafast hydrogen bond dynamics in real-time and to separate different microscopic couplings in the nonlinear response [3,4]. Quantum coherent vibrational dynamics of hydrogen bonds in liquids is a topic of substantial current interest [5] and both coherent nuclear motions, i.e., vibrational wavepackets, and processes of vibrational dephasing and relaxation have been studied recently by ultrafast pump-probe and Hydrogen-Transfer Reactions. Edited by

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“…The contemporary theoretical models, proposed for quantitative description of spectral properties of hydrogen bond systems, namely the ''strong-coupling'' theory [5][6][7][8], or the much novel ''relaxation'' theory [9][10][11][12][13][14], were generally able to satisfactorily explain some basic spectral properties of hydrogen bonds, including a quantitative reproduction of the m X-H band shapes. However, there are a number of spectral effects in the vibrational spectra, which seems to be beyond the reach of a purely vibrational approach assumed by these two models.…”

Section: Introductionmentioning

confidence: 99%

“…However, the latest studies on the residual m X-H bands have suggested that a new kind of H/D isotopic effects for hydrogen bond systems existed, namely the so called isotopic ''self-organization'' effects [15][16][17][18][19]. For the first time these effects were revealed for cyclic, centrosymmetric dimeric systems of hydrogen bonds, for which the shapes of residual m X-H bands remained almost invariant, when the deuterium substitution rate increased; such behavior remained in contrast with predictions of the most recent advanced theoretical models [5][6][7][8][9][10][11][12][13]20,21].…”

Section: Introductionmentioning

confidence: 99%

Vibronic model for H/D isotopic “self-organization” effects in hydrogen bond cyclic trimeric systems: 4-Bromopyrazole crystal IR spectra

Flakus

Pyzik

2006

Chemical Physics

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Infrared spectra of weak H-bonds: beyond an adiabatic description of Fermi resonances

Cited by 76 publications

References 15 publications

CH⋅⋅⋅O Hydrogen Bonds in Cyclohexenone Reveal the Spectroscopic Behavior of CH and CH Donors

CH⋅⋅⋅O Hydrogen Bonds in Cyclohexenone Reveal the Spectroscopic Behavior of CH and CH Donors

Coherent Low‐frequency Motions in Condensed Phase Hydrogen Bonding and Transfer

Vibronic model for H/D isotopic “self-organization” effects in hydrogen bond cyclic trimeric systems: 4-Bromopyrazole crystal IR spectra

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