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Hydrophobic Molecules Slow Down the Hydrogen-Bond Dynamics of Water

Bakulin, A. A., Pshenichnikov, M. S., Bakker, H. J. & Petersen, C., 17-Mar-2011, In : The Journal of Physical Chemistry A. 115, 10, p. 1821-1829 9 p.

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We study the spectral and orientational dynamics of HDO molecules in solutions of tertiarybutyl-alcohol (TBA), trimethyl-amine-oxide (TMAO), and tetramethylurea (TMU) in isotopically diluted water (HDO:D(2)O and HDO:H(2)O). The spectral dynamics are studied with femtosecond two-dimensional infrared spectroscopy and the orientational dynamics with femtosecond polarization-resolved vibrational pump probe spectroscopy. We observe a strong slowing down of the spectral diffusion around the central part of the absorption line that increases with increasing solute concentration. At low concentrations, the fraction of water showing slow spectral dynamics is observed to scale with the number of methyl groups, indicating that this effect is due to slow hydrogen-bond dynamics in the hydration shell of the methyl groups of the solute molecules. The slowing down of the vibrational frequency dynamics is strongly correlated with the slowing down of the orientational mobility of the water molecules. This correlation indicates that these effects have a common origin in the effect of hydrophobic molecular groups on the hydrogen-bond dynamics of water.

Original languageEnglish
Pages (from-to)1821-1829
Number of pages9
JournalThe Journal of Physical Chemistry A
Volume115
Issue number10
Publication statusPublished - 17-Mar-2011

    Keywords

  • TERT-BUTYL ALCOHOL, LIQUID WATER, AQUEOUS-SOLUTIONS, INFRARED-SPECTROSCOPY, REORIENTATION, HYDRATION, SOLUTES, BUTANOL, PROBE, SIMULATIONS

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