Ultrafast Dynamics of the Carbonyl Stretching Vibration in Acetic Acid in Aqueous Solution Studied by Sub-Picosecond Infrared Spectroscopy

The Journal of Chemical Physics

Tominaga

2015

Self Cite

Recently, biomolecules which are labeled by azide or thiocyanate groups in solutions and proteins have been studied to examine microscopic environment around a solute by nonlinear infrared (IR) spectroscopy. In this study, we have performed two-dimensional infrared (2D-IR) spectroscopy to investigate the vibrational frequency fluctuations of two different azide-derivatized amino acids, Ala (N3-Ala) and Pro (N3-Pro), and N3(-) in water. From the 2D-IR experiments, it was found that the frequency-frequency time correlation function (FFTCF) of solute can be modeled by a delta function plus an exponential function and constant. FFTCF for each probe molecule has a decay component of about 1 ps, and this result suggests that the stretching mode of the covalently bonded azide group is sensitive to the fluctuations of hydrogen bond network system, as found in previous studies of N3(-) in water. In contrast to FFTCF of N3(-), FFTCF of the azide-derivatized amino acids contains static component. This static component may reflect dynamics of water affected by the solutes or the structural fluctuations of the solute itself. We also performed the IR pump-probe measurements for the probe molecules in water in order to investigate vibrational energy relaxation (VER) and reorientational relaxation. It was revealed that the charge fluctuations in the azide group are significant for the VER of this mode in water, reflecting that the VER rate of N3(-) is faster than those of the azide-derivatized amino acids. While the behaviors of the anisotropy decay of N3-Ala and N3(-) are similar to each other, the anisotropy decay of N3-Pro contains much slower decaying component. By considering the structural difference around the vibrational probe between N3-Ala and N3-Pro, it is suggested that the structural freedom of the probe molecules can affect the reorientational processes.

Section: Methodsmentioning

confidence: 99%

Vibrational dynamics of azide-derivatized amino acids studied by nonlinear infrared spectroscopy

Okuda

The Journal of Chemical Physics

Tominaga

2015

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“…The details of the apparatus are described elsewhere. 17 Briefly, IR pulses were generated by difference frequency mixing between the signal and the idler pulses from an optical parametric amplifier, pumped by a Ti : sapphire regenerative amplifier. The IR pulse was separated into three pulses: the pump, the probe, and the reference pulses.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast vibrational dynamics and solvation complexes of methyl acetate in methanol studied by sub‐picosecond infrared spectroscopy

Banno

Tominaga

2008

J Raman Spectroscopy

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The vibrational dynamics of the CO stretching mode of methyl acetate (MA) in methanol was studied by time-resolved infrared (IR) pump-probe spectroscopy. The vibrational energy relaxation (VER) process includes two components with time constants of 1.3 ± 0.1 and 4.0 ± 0.2 ps. These components result from the vibrational excitations of the hydrogen-bonding complex of MA with one methanol and the MA monomer, respectively. The difference in the VER time is explained by the increase of the vibrational density of states (VDOS) by the intermolecular hydrogen bond. The time constants and the decayassociated spectra are almost identical between the CH 3 OH and the CH 3 OD solutions. The vibrational modes localized in the intramolecular OH/OD bond of the solvent methanol have little effect on the vibrational dynamics of MA.

“…The details of the experimental setup for the IR pump-probe and three-pulse IR photon-echo experiments are described elsewhere [3,7,8]. Briefly, a mid-IR pulse was generated by the difference frequency generation on an AgGaS 2 crystal between the two near-IR outputs, signal and idler pulse, of an optical parametric amplifier.…”

Section: Methodsmentioning

confidence: 99%

Vibrational dynamics of the CN stretching mode of [Ru(CN)6]4− in D2O studied by nonlinear infrared spectroscopy

Tayama

Banno

Sci. China Phys. Mech. Astron.

et al. 2010

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We have studied vibrational dynamics of the T 1u mode of the CN stretching mode of [Ru(CN) 6 ] 4− in D 2 O by infrared (IR) nonlinear spectroscopy such as an IR three-pulse photon echo experiment and polarization-sensitive IR pump-probe spectroscopy. The isotropic component of the pump-probe signal shows a bi-exponential decay with time constants of 0.8 ps and 20.8 ps. The fast and slow components correspond to the rapid equilibration between the T 1u mode and the Raman active modes of the CN stretching mode and the vibrational population relaxation from the v = 1 state of the T 1u mode, respectively. Anisotropy of the pump-probe signal decays with a time constant of 3.1 ps, which is due to the time evolution of the superposition states of the triply degenerate T 1u modes. Three pulse photon echo measurements showed that the time correlation function of the frequency fluctuation decays bi-exponentially with time constants of 80 fs and 1.4 ps. These time constants depend only on the solute and are independent of the solvent, whereas the amplitudes depend on both the solute and solvent.nonlinear IR spectroscopy, metal complex, aqueous solution PACS: 78.47.jh