Department of Physical Chemistry, University of Granada, Cartuja Campus, 18071 Granada, Spain.
Phys Chem Chem Phys. 2011 Jan 28;13(4):1685-94. doi: 10.1039/c0cp01232g. Epub 2010 Dec 22.
The buffer-mediated proton-transfer reactions of the fluorescent xanthenic derivative 9-[1-(2-Methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II) have been studied in different aqueous media. We have employed various buffers to investigate the influence of donor/acceptor systems with different anion and/or cation chemical constituents on the kinetic parameters of proton-transfer. The kinetic parameters were recovered both in the ground-state by means of Fluorescence Lifetime Correlation Spectroscopy (FLCS) and in the excited-state by means of Time Correlated Single Photon Counting (TCSPC) and Global Compartmental Analysis (GCA). Both ground- and excited- deprotonation and protonation recovered rate constants in the presence of either phosphate or acetate buffer as donor/acceptor systems were similar. The presence of Tris-HCl buffer does not promote the excited-state proton-transfer (ESPT) reaction. The results indicate the influence of the ions on the ground-state proton-transfer (GSPT) rates and concomitantly on the ESPT reaction. The proton-transfer rate constants recovered here show a trend correlated with the Hofmeister series or the Marcus classification of ions.
荧光呫吨衍生物 9-[1-(2-甲基-4-甲氧基苯基)]-6-羟基-3H-呫吨-3-酮（TG-II）的缓冲介导质子转移反应已在不同的水介质中进行了研究。我们采用了各种缓冲液来研究具有不同阴离子和/或阳离子化学组成的供体/受体系统对质子转移动力学参数的影响。通过荧光寿命相关光谱（FLCS）和时间相关单光子计数（TCSPC）和全局分区分析（GCA）在基态和激发态下都恢复了动力学参数。在磷酸盐或乙酸盐缓冲液作为供体/受体系统存在的情况下，均恢复了基态和激发态去质子化和质子化的恢复速率常数。三羟甲基氨基甲烷盐酸盐缓冲液的存在并不促进激发态质子转移（ESPT）反应。结果表明离子对基态质子转移（GSPT）速率的影响以及对 ESPT 反应的影响。这里恢复的质子转移速率常数表现出与Hofmeister 系列或离子的Marcus 分类相关的趋势。
