Excited-State Proton-Transfer Processes of DHICA Resolved: From Sub-Picoseconds to Nanoseconds

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• 作者：Alice Corani ; Alessandro Pezzella ; Torbj枚rn Pascher ; Thomas Gustavsson ; Dimitra Markovitsi ; Annemarie Huijser ; Marco d鈥橧schia ; Villy Sundstr枚m
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2013
• 出版时间：May 2, 2013
• 年：2013
• 卷：4
• 期：9
• 页码：1383-1388
• 全文大小：340K
• 年卷期：v.4,no.9(May 2, 2013)
• ISSN：1948-7185

文摘

Excited-state proton transfer has been hypothesized as a mechanism for UV energy dissipation in eumelanin skin pigments. By using time-resolved fluorescence spectroscopy, we show that the previously proposed, but unresolved, excited-state intramolecular proton transfer (ESIPT) of the eumelanin building block 5,6-dihydroxyindole-2-carboxylic acid (DHICA) occurs with a time constant of 300 fs in aqueous solution but completely stops in methanol. The previously disputed excited-state proton transfer involving the 5- or 6-OH groups of the DHICA anion is now found to occur from the 6-OH group to aqueous solvent with a rate constant of 4.0 脳 10⁸ s^鈥?.

Keywords:

DHICA; ESPT; solvent; time-resolved fluorescence; eumelanin