Highlights
• The excited-state proton transfer (ESPT) to water time-constant of the photoacid is 160 fs.
• The kinetic isotope effect in H2O and D2O is 1.7.
• Intermolecular donor-acceptor vibration controls the ESPT rate.
Abstract
Steady-state and time-resolved fluorescence techniques were employed to study the photoacidity of a newly synthesized photoacid, the chloro benzoate cyanine picolinium salt.
It was found that the ESPT rate constant is ultrafast in water (kPT = 6.2 × 1012s−1). We also found that the kinetic isotope effect is ∼1.7. The deprotonated form of the photoacid has a short lifetime of about 95 ps.
