Ultrafast Excited-State Intermolecular Proton Transfer of Cyanine Fluorochrome Dyes

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• 作者：Naama Karton-Lifshin ; Itay Presiado ; Yuval Erez ; Rinat Gepshtein ; Doron Shabat ; Dan Huppert
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：January 12, 2012
• 年：2012
• 卷：116
• 期：1
• 页码：85-92
• 全文大小：486K
• 年卷期：v.116,no.1(January 12, 2012)
• ISSN：1520-5215

文摘

Steady-state and time-resolved emission spectroscopy techniques were employed to study the excited-state proton transfer (ESPT) to water and D₂O 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 脳 10¹² s^鈥?. 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, 蟿_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.