Ultrafast excited-state intermolecular proton transfer of cyanine fluorochrome dyes

Naama Karton-Lifshin, Itay Presiado, Yuval Erez, Rinat Gepshtein, Doron Shabat, Dan Huppert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Steady-state and time-resolved emission spectroscopy techniques were employed to study the excited-state proton transfer (ESPT) to water and D 2O from QCy7, a recently synthesized near-infrared (NIR)-emissive dye with a fluorescence band maximum at 700 nm. We found that the ESPT rate constant, k PT, of QCy7 excited from its protonated form, ROH, is ∼1.5 × 10 12 s -1. This is the highest ever reported value in the literature thus far, and it is comparable to the reciprocal of the longest solvation dynamics time component in water, τ S = 0.8 ps. We found a kinetic isotope effect (KIE) on the ESPT rate of ∼1.7. This value is lower than that of weaker photoacids, which usually have KIE value of ∼3, but comparable to the KIE on proton diffusion in water of ∼1.45, for which the average time of proton transfer between adjacent water molecules is similar to that of QCy7.

Original languageEnglish
Pages (from-to)85-92
Number of pages8
JournalJournal of Physical Chemistry A
Issue number1
StatePublished - 12 Jan 2012


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