Photoprotolytic Processes of Lumazine

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• 作者：Ron Simkovitch ; Dan Huppert
• 刊名：Journal of Physical Chemistry B
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：121
• 期：1
• 页码：129-142
• 全文大小：772K
• ISSN：1520-5207

文摘

Steady-state and time-resolved UV–vis spectroscopies were used to study the photoprotolytic properties of lumazine, which belongs to a class of biologically important compounds—the petridines. We found that in water an excited-state proton transfer occurs with a time constant of ∼70 ps and competes with a nonradiative rate of about the same value. The nonradiative rate of the protonated form of lumazine in polar and nonpolar solvents is large k_nr ≥ 1.5 × 10¹⁰s^–1. The fluorescence properties indicate that in water, the ground-state neutral form of lumazine is already stable in two tautomeric forms. The fluorescence of the deprotonated form is quenched by protons in acidic solutions with a diffusion-controlled reaction rate. We conclude that the neutral form of lumazine is an irreversible mild photoacid.