title: Influence of the solvent on the ground- and excited-state buffer-mediated proton-transfer reactions of a xanthenic dye.
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.
authors.affiliation: Department of Physical Chemistry, University of Granada, Cartuja Campus, 18071 Granada, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Paredes
authors.forename: Luis
authors.initials: L
authors.lastname: Crovetto
authors.forename: Angel
authors.initials: A
authors.lastname: Orte
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alvarez-Pez
authors.forename: Eva M
authors.initials: EM
authors.lastname: Talavera
mesh_terms: D002021:Buffers; D004396:Coloring Agents / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D044004:Xanthones / Q000737:chemistry*
chemical_list: C543496:9-(1-(2-methyl-4-methoxyphenyl))-6-hydroxy-3H-xanthen-3-one; D002021:Buffers; D004396:Coloring Agents; D011522:Protons; D012997:Solvents; D044004:Xanthones