Solvent dependence of excited-state proton transfer from pyranine-derived photoacids

Christian Spies, Shay Shomer, Björn Finkler, Dina Pines, Ehud Pines*, Gregor Jung, Dan Huppert

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Steady-state and time-resolved techniques were employed to study the excited-state proton-transfer (ESPT) rate of two newly synthesized 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine, HPTS) derived photoacids in three protic solvents, water, methanol and ethanol. The ESPT rate constant k PT of tris(1,1,1,3,3,3-hexafluoropropan-2-yl)-8-hydroxypyrene-1,3,6- trisulfonate, 1a, whose pKa* ∼ -4, in water, methanol and ethanol is 3 × 1011 s-1, 8 × 109 s-1 and 5 × 109 s-1 respectively. (8-Hydroxy-N1,N3,N6-tris(2-hydroxyethyl)-N1,N3,N6-trimethylpyrene-1,3,6 trisulfonamide, 1b) is a weaker acid than 1a but still a strong photoacid with pKa* ∼ -1 and the ESPT rate in water, methanol and ethanol is 7 × 1010 s-1, 4 × 108 s -1 and 2 × 108 s-1. We qualitatively explain our kinetic results by a Marcus-like free-energy correlation which was found to have a general form suitable for describing proton transfer reactions in both the proton-adiabatic and the proton-non-adiabatic limits. This journal is

Original languageEnglish
Pages (from-to)9104-9114
Number of pages11
JournalPhysical Chemistry Chemical Physics
Issue number19
StatePublished - 21 May 2014


FundersFunder number
German Academic Exchange Service


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