Dynamics of solvent response in methanol-chloroform binary solvent mixture: A case of synergistic solvation

Shradhey Gupta, Shahnawaz Rafiq, Pratik Sen

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42 Scopus citations


Steady-state absorption, emission, and femtosecond transient absorption spectroscopies were used to ascertain the static and dynamic nature of the solvent response of methanol-chloroform binary solvent mixtures of different stoichiometric ratios using 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) as the probe molecule. The appearance of synergistic solvation behavior in the steady-state absorption measurements can be explained in terms of solvent-solvent interactions through an extended hydrogen-bonding network. The disappearance of such synergistic behavior in the excited state of the DCM dye was recently proposed by us to be due to the weak nature of the intermolecular interactions present in binary solvent mixtures (J. Phys. Chem. B 2012, 116, 1345). It was anticipated and subsequently confirmed by the dynamics of the solvent response that the disruption of the weak interactive solvent network is the main reason for the absence of the synergism in the excited state. As expected, we observed the slowest dynamics for the mixture with XMeOH = 0.45, with an average solvation time of 12.03 ps, which is much higher than the values for the pure bulk counterparts (〈τsMethanol = 4.32 ps and 〈τsChloroform = 1.32 ps). The unprecedented slowing of solvation for DCM is probably due to the rigid interactive methanol-chloroform solvent system in the first solvation shell, followed by solvent rearrangements around the solute dipole. Overall interactions present within the methanol-chloroform binary solvent mixture furnish clear evidence of solvent association through weak hydrogen bonding.

Original languageEnglish
Pages (from-to)3135-3141
Number of pages7
JournalJournal of Physical Chemistry B
Issue number7
StatePublished - Feb 19 2015

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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