Influence of the solvent on the ground- and excited-state buffer-mediated proton-transfer reactions of a xanthenic dye

Phys Chem Chem Phys. 2011 Jan 28;13(4):1685-94. doi: 10.1039/c0cp01232g. Epub 2010 Dec 22.

Abstract

The buffer-mediated proton-transfer reactions of the fluorescent xanthenic derivative 9-[1-(2-Methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II) have been studied in different aqueous media. We have employed various buffers to investigate the influence of donor/acceptor systems with different anion and/or cation chemical constituents on the kinetic parameters of proton-transfer. The kinetic parameters were recovered both in the ground-state by means of Fluorescence Lifetime Correlation Spectroscopy (FLCS) and in the excited-state by means of Time Correlated Single Photon Counting (TCSPC) and Global Compartmental Analysis (GCA). Both ground- and excited- deprotonation and protonation recovered rate constants in the presence of either phosphate or acetate buffer as donor/acceptor systems were similar. The presence of Tris-HCl buffer does not promote the excited-state proton-transfer (ESPT) reaction. The results indicate the influence of the ions on the ground-state proton-transfer (GSPT) rates and concomitantly on the ESPT reaction. The proton-transfer rate constants recovered here show a trend correlated with the Hofmeister series or the Marcus classification of ions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Buffers
  • Coloring Agents / chemistry*
  • Protons*
  • Solvents / chemistry*
  • Spectrometry, Fluorescence
  • Xanthones / chemistry*

Substances

  • 9-(1-(2-methyl-4-methoxyphenyl))-6-hydroxy-3H-xanthen-3-one
  • Buffers
  • Coloring Agents
  • Protons
  • Solvents
  • Xanthones