The photoacidity of phenol chloro benzoate cyanine picolinium salt photoacid in alkanols

Oren Gajst, Ori Green, Ron Simkovitch, Doron Shabat, Dan Huppert

Research output: Contribution to journalArticlepeer-review

Abstract

Steady-state and time-resolved fluorescence techniques were employed to study the excited-state proton transfer (ESPT) rate to methanol, ethanol and propanol of a new photoacid, the chloro benzoate phenol cyanine picolinium salt (CBCyP). We found that the ESPT rate constants for methanol, ethanol and propanol are about 3 × 1012 s−1, 2 × 1012 s−1 and 1.2 × 1012 s−1 respectively, whereas for water it is 6 × 1012 s−1. The photoacid pKa* in water is about pKa ∼ −7. The kinetic isotope effect as measured from the fluorescence decay rate of the protonated form is 1.5 and 1.25 for methanol and ethanol respectively, whereas in water it is 1.7. We suggest that a nonradiative process takes place and reduces the measured kinetic isotope effect in both methanol and ethanol.

Original languageEnglish
Pages (from-to)546-556
Number of pages11
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume353
DOIs
StatePublished - 15 Feb 2018

Keywords

  • Excited-state proton transfer
  • Kinetic isotope effect
  • Nonradiative rate
  • Photoacid
  • Time-resolved fluorescence

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