title: Ultrafast excited-state intermolecular proton transfer of cyanine fluorochrome dyes.
abstract: Steady-state and time-resolved emission spectroscopy techniques were employed to study the excited-state proton transfer (ESPT) to water and D(2)O 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.
authors: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
authors: Naama
authors: N
authors: Karton-Lifshin
authors: Itay
authors: I
authors: Presiado
authors: Yuval
authors: Y
authors: Erez
authors: Rinat
authors: R
authors: Gepshtein
authors: Doron
authors: D
authors: Shabat
authors: Dan
authors: D
authors: Huppert