Chloro benzoate cyanine picolinium photoacid excited-state proton transfer to water

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 ( k PT  = 6.2 × 10 12 s −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.