Water-Induced Relaxation of a Degenerate Vibration of Guanidinium Using 2D IR Echo Spectroscopy

Vorobyev, Dmitriy Yu.; Kuo, Chun-Hung; Kuroda, Daniel G.; Scott, J. Nathan; Vanderkooi, Jane M.; Hochstrasser, Robin M.

doi:10.1021/jp909531s

Cited by 40 publications

(90 citation statements)

References 41 publications

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“…In a study of guanidinium in water and water-glycerol mixtures, Hochstrasser and coworkers have recently analyzed in detail the effects of excitation versus energy transfer on the anisotropy of 2D-IR and dispersed photon echo signals of a quasi-degenerate mode 23 . They concluded that in their case fast anisotropy decay is primarily caused by excitation transfer, whereas reorientation of the transition dipole moments is slower.…”

Section: Discussionmentioning

confidence: 99%

“…A similar approach was recently taken by Hochstrasser and co-workers, who investigated the water-induced relaxation of Guanidinium (D 3 -symmetry). 23 Compared to their study, the nitrate ion offers the advantage of a much larger solvent-induced splitting of the degenerate vibrations, already in pure water (see below), which also allows us to better differentiate between excitation transfer and normal mode mixing processes.…”

Section: Introductionmentioning

confidence: 99%

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Hydration Dynamics of Aqueous Nitrate

et al. 2013

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Aqueous nitrate, NO3-(aq), was studied by 2D-IR, UV-IR, and UV-UV time-resolved spectroscopies in combination with molecular dynamics (MD) simulations with the purpose of determining the hydration dynamics around the anion. In water, the D3h symmetry of NO3-is broken, and the degeneracy of the asymmetric-stretch modes is lifted. This provides a very sensitive probe of the ionwater interactions. The 2D-IR measurements reveal excitation exchange between the two nondegenerate asymmetric-stretch vibrations on a 300-fs time scale concomitant with fast anisotropy decay of the diagonal-peak signals. The MD simulations show that this is caused by jumps of the transition dipole orientations related to fluctuations of the hydrogen bonds connecting the nitrate ion to the nearest water molecules. Reorientation of the ion, which is associated with the hydrogen-bond breaking, was monitored by time-resolved UV-IR and UV-UV spectroscopy, revealing a 2-ps time constant. These time scales are very similar to those reported for isotope-labeled water, suggesting that NO3-(aq) has a labile hydration shell. connecting the nitrate ion to the nearest water molecules. Reorientation of the ion, which is associated with the hydrogen bond breaking, is monitored by time resolved UV-IR-and UV-UV spectroscopy, revealing a 2 ps time constant. These time scales are very similar to those reported for isotope-labeled water, suggesting that NO 3¯( aq) has a labile hydration shell.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydration Dynamics of Aqueous Nitrate

et al. 2013

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“…However, to the best of our knowledge, the concept of a CI has not been used in the context of vibrational adiabatic states. Jahn-Teller type of coupling has been discussed in the context of vibrational transitions [24,25], which in fact leads to a CI dictated by symmetry, but that connection has not been made. In this Letter, we derive the conditions that such an intersection occurs, present quantum-dynamical model calculations to show the consequences for the vibrational dynamics and spectra, and demonstrate via ab initio calculations that low-lying vibrational CIs indeed exist in concrete molecular systems.…”

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confidence: 99%

“…We require at least two HF modes to assure that two vibrational states may become degenerate, either by symmetry via a Jahn-Teller type of coupling [24,25] or accidentally (which is the case we will focus on). On the other hand, at least two LF modes are needed because the hypersurface of a CI is N -2-dimensional (N being the number of LF modes).…”

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confidence: 99%

Vibrational Conical Intersections as a Mechanism of Ultrafast Vibrational Relaxation

Hamm

Stock

2012

Phys. Rev. Lett.

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Presenting true crossings of adiabatic potential energy surfaces, conical intersections are a paradigm of ultrafast and efficient electronic relaxation dynamics. The same mechanism is shown to apply also for vibrational conical intersections, which may occur when two high-frequency modes (such as OH stretch vibrations) are coupled to low-frequency modes (such as hydrogen bonding modes). By derivation of a model Hamiltonian and its parametrization for a concrete example, malonaldehyde, the conditions that such conical intersections occur are identified and the consequences for the vibrational dynamics and spectra are demonstrated.

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“…2,3 Due to the sensitivity to local environment and time resolution, ultrafast vibrational spectroscopy is now the method of choice for studying rapid dynamical processes of molecular ions in water. [4][5][6] Several different ions have been investigated using time resolved vibrational spectroscopy (e.g., cyanide, 7,8 azide, 9, 10 thyocyanate, 11 guanidinium, 12,13 trifluoroacetate, 14 tricyanomethanide, 6 etc.). However, only a few studies have focused directly on the effect of the water motions, when the a) Authors to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Vibrational dynamics of a non-degenerate ultrafast rotor: The (C12,C13)-oxalate ion

Kuroda

Abdo

Chuntonov

et al. 2013

The Journal of Chemical Physics

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Molecular ions undergoing ultrafast conformational changes on the same time scale of water motions are of significant importance in condensed phase dynamics. However, the characterization of systems with fast molecular motions has proven to be both experimentally and theoretically challenging. Here, we report the vibrational dynamics of the non-degenerate (C12,C13)-oxalate anion, an ultrafast rotor, in aqueous solution. The infrared absorption spectrum of the (C12,C13)-oxalate ion in solution reveals two vibrational transitions separated by approximately 40 cm −1 in the 1500-1600 cm −1 region. These two transitions are assigned to vibrational modes mainly localized in each of the carboxylate asymmetric stretch of the ion. Two-dimensional infrared spectra reveal the presence and growth of cross-peaks between these two transitions which are indicative of coupling and population transfer, respectively. A characteristic time of sub-picosecond cross-peaks growth is observed. Ultrafast pump-probe anisotropy studies reveal essentially the same characteristic time for the dipole reorientation. All the experimental data are well modeled in terms of a system undergoing ultrafast population transfer between localized states. Comparison of the experimental observations with simulations reveal a reasonable agreement, although a mechanism including only the fluctuations of the coupling caused by the changes in the dihedral angle of the rotor, is not sufficient to explain the observed ultrafast population transfer.

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Water-Induced Relaxation of a Degenerate Vibration of Guanidinium Using 2D IR Echo Spectroscopy

Cited by 40 publications

References 41 publications

Hydration Dynamics of Aqueous Nitrate

Hydration Dynamics of Aqueous Nitrate

Vibrational Conical Intersections as a Mechanism of Ultrafast Vibrational Relaxation

Vibrational dynamics of a non-degenerate ultrafast rotor: The (C12,C13)-oxalate ion

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