Hydrogen Bond Dissociation and Reformation in Methanol Oligomers Following Hydroxyl Stretch Relaxation

Gaffney, Kelly J.; Davis, Paul H.; Piletic, Ivan R.; Levinger, Nancy E.; Fayer, M. D.

doi:10.1021/jp021696g

Cited by 95 publications

(208 citation statements)

References 53 publications

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“…However, there is no signature of such processes in the experimental data ( Figure 7). Furthermore, the subsequent restoration of the broken hydrogen bond results in the opposite trends in the pump-probe signals, 29 again in clear contradiction with our experimental data. In contrast, the proposed model explains self-consistently the transient absorption data ( Figures 5 and 7) and absorption spectra (Figure 8), and yields predictions on the mixture composition that are in accord with MD simulations (Figure 9).…”

Section: /T 1 Non-water-bonded )contrasting

confidence: 99%

“…This process is analogous to the theoretically predicted and experimentally observed VER in alcohols, where energy transfer directly to the hydrogen bond leads to its subsequent rupture. [27][28][29][30][31][32][33] The OH-stretching mode dynamics in heavy water has also been studied by an IR pump visible probe pulse technique. 2,23 In this method, a femtosecond IR pump pulse excites the vibrational transition while the response of the system is monitored via spontaneous Raman scattering induced by a visible probe pulse.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

et al. 2004

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We present a study of the effect of hydrogen bonding on vibrational energy relaxation of the OH-stretching mode in pure water and in water-acetonitrile mixtures. The extent of hydrogen bonding is controlled by dissolving water at various concentrations in acetonitrile. Infrared frequency-resolved pump-probe measurements were used to determine the relative abundance of hydrogen-bonded versus non-hydrogen-bonded OH bonds in water-acetonitrile mixtures. Our data show that the main pathway for vibrational relaxation of the OH-stretching mode in pure water involves the overtone of the bending mode. Hydrogen bonding is found to accelerate the population relaxation from 3 ps in dilute solutions to 700 fs in neat water, as a result of increasing overlap between donor and acceptor modes. Hydroxyl groups that initially are not hydrogen bonded have two relaxation pathways: by direct nonresonant relaxation to the bending mode with a time constant of 12 ps or by making a hydrogen bond to a neighboring water molecule first (∼2 ps) and then relaxing as a hydrogen-bonded OH oscillator.

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Section: /T 1 Non-water-bonded )contrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

et al. 2004

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“…Ethanol-OD in ethanol-OH has an OD-stretch T 1 of 800 fs (Ref. 44) and methanol-OD in methanol-OH of 500 fs, 45 both of which agree well with the 810 fs for the fast component that we observe. To confirm our hypothesis that the fast component is due to Igepal, we also measured the transient response of the OD-stretch vibration in neat Igepal, which reveals a similar fast component of 1.2 ps.…”

Section: Resultssupporting

confidence: 82%

Structure and dynamics of water in nonionic reverse micelles: A combined time-resolved infrared and small angle x-ray scattering study

Loop

Panman

Lotze

et al. 2012

The Journal of Chemical Physics

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We study the structure and reorientation dynamics of nanometer-sized water droplets inside nonionic reverse micelles (water/Igepal-CO-520/cyclohexane) with time-resolved mid-infrared pumpprobe spectroscopy and small angle x-ray scattering. In the time-resolved experiments, we probe the vibrational and orientational dynamics of the O-D bonds of dilute HDO:H 2 O mixtures in Igepal reverse micelles as a function of temperature and micelle size. We find that even small micelles contain a large fraction of water that reorients at the same rate as water in the bulk, which indicates that the polyethylene oxide chains of the surfactant do not penetrate into the water volume. We also observe that the confinement affects the reorientation dynamics of only the first hydration layer. From the temperature dependent surfacewater dynamics, we estimate an activation enthalpy for reorientation of 45 ± 9 kJ mol −1 (11 ± 2 kcal mol −1 ), which is close to the activation energy of the reorientation of water molecules in ice.

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“…This picture of heat diffusion out of the reverse micelles, thereby causing the long-lived signal to decay, is consistent with observations of hydrogen-bond dissociation and reformation dynamics of methanol oligomers in CCl 4 . 78 It is interesting to contrast these results with those presented by Dlott and co-workers, 45 who examined the vibrational cascade of the excited OH stretch of H 2 O in AOT reverse micelles. The experiments measure the vibrational relaxation of two different fundamental transitions: the OD stretch of HOD in the experiments described in this paper and the OH stretch of H 2 O in the work presented by Dlott and co-workers.…”

Section: Resultsmentioning

confidence: 84%

“…Table 1 contains the vibrational lifetimes (T 1 ) for the three reverse micelles, bulk water, and the NaCl solution. In hydrogen-bonded liquids, the vibrational lifetime is not trivial to measure, because the pump-probe experiment can be sensitive to spectral dynamics in the ground and excited state 62 and hydrogen bond dissociation, 69,78,79 in addition to vibrational relaxation. If a frequency-selected subset of the water molecules is excited by a relatively narrow pump pulse, then spectral diffusion in the ground and excited state will produce a frequency-dependent signal.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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The dynamics of water in nanoscopic pools 1.7-4.0 nm in diameter in AOT reverse micelles were studied with ultrafast infrared spectrally resolved stimulated vibrational echo and pump-probe spectroscopies. The experiments were conducted on the OD hydroxyl stretch of low-concentration HOD in the H 2 O, providing a direct examination of the hydrogen-bond network dynamics. Pump-probe experiments show that the vibrational lifetime of the OD stretch mode increases as the size of the reverse micelle decreases. These experiments are also sensitive to hydrogen-bond dissociation and reformation dynamics, which are observed to change with reverse micelle size. Spectrally resolved vibrational echo data were obtained at several frequencies. The vibrational echo data are compared to data taken on bulk water and on a 6 M NaCl solution, which is used to examine the role of ionic strength on the water dynamics in reverse micelles. Two types of vibrational echo measurements are presented: the vibrational echo decays and the vibrational echo peak shifts. As the water nanopool size decreases, the vibrational echo decays become slower. Even the largest nanopool (4 nm, ∼1000 water molecules) has dynamics that are substantially slower than bulk water. It is demonstrated that the slow dynamics in the reverse micelle water nanopools are a result of confinement rather than ionic strength. The data are fit using time-dependent diagrammatic perturbation theory to obtain the frequency-frequency correlation function (FFCF) for each reverse micelle. The results are compared to the FFCF of water and show that the largest differences are in the slowest time scale dynamics. In bulk water, the slowest time scale dynamics are caused by hydrogen-bond network equilibration, i.e., the making and breaking of hydrogen bonds. For the smallest nanopools, the longest time scale component of the water dynamics is ∼10 times longer than the dynamics in bulk water. The vibrational echo data for the smallest reverse micelle displays a dependence on the detection wavelength, which may indicate that multiple ensembles of water molecules are being observed.

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Hydrogen Bond Dissociation and Reformation in Methanol Oligomers Following Hydroxyl Stretch Relaxation

Cited by 95 publications

References 53 publications

Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

Structure and dynamics of water in nonionic reverse micelles: A combined time-resolved infrared and small angle x-ray scattering study

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

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