Ultrafast Excited-State Proton-Transfer Reaction of 1-Naphthol-3,6-Disulfonate and Several 5-Substituted 1-Naphthol Derivatives

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• 作者：Mirabelle Pr茅mont-Schwarz ; Tamar Barak ; Dina Pines ; Erik T. J. Nibbering ; Ehud Pines
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：April 25, 2013
• 年：2013
• 卷：117
• 期：16
• 页码：4594-4603
• 全文大小：492K
• 年卷期：v.117,no.16(April 25, 2013)
• ISSN：1520-5207

文摘

The 1-naphthol molecule has been the subject of intense research activity for the past 60 years due to its complex behavior as a photoacid upon optical excitation. We have utilized femtosecond mid-infrared spectroscopy and time-resolved fluorescence spectroscopy to investigate the excited-state proton-transfer reaction of 1-naphthol-3,6-disulfonate (1N-3,6diS) and several 5-substituted 1-naphthol derivatives. The proton dissociation rate constant of 1N-3,6-diS was found to be about 3 times faster and the pK_a* about 2 pK_a units more acidic than the values previously reported in the literature. A Marcus (free-energy) plot of excited-state proton dissociation rate constants vs the excited-state equilibrium constant of the photoacids, K_a*, was constructed using the C-5 series of 1-naphthol derivatives. The newly measured values for the ESPT rate constant and pK_a* of 1N-3,6diS was found to fit well with the Marcus correlation. We discuss our findings in the context of the photoacidity phenomenon in general, and the photoacidity of 1-naphthol and its derivatives in particular.