Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-Methylbutyl)aminodipicolinic Acid (H2MEBADPA)

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• 作者：Andrew J. Ingram ; Alexander G. Dunlap ; Richard DiPietro ; Gilles Muller
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：July 14, 2011
• 年：2011
• 卷：115
• 期：27
• 页码：7912-7920
• 全文大小：978K
• 年卷期：v.115,no.27(July 14, 2011)
• ISSN：1520-5215

文摘

4-(2-Methylbutyl)aminodipicolinic acid (H₂MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pK_a's) and photophysical measurements. The pK_a's were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA^{2鈥?/sup> is appreciably emissive. The fluorescence of MEBADPA2鈥?/sup> has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pK_as and quenching constants, the fluorescent intensity of MEBADPA2鈥?/sup> has been successfully modeled as a function of pH.}