荧光素蒽醌甲酯分子内光诱导电子转移及电荷分离态的检测

Photo-induced Intramolecular Electron Transfer of Fluorescein-anthraquinone-methyl Ester and Detection of Its Charge-separated State

合成了以荧光素为光敏剂的电子给体 -受体二元化合物荧光素蒽醌甲酯 (FL-AQ) ,用吸收光谱、荧光光谱、荧光寿命研究了该化合物在乙醇溶液中的光物理性质 ,并首次用纳秒级瞬态吸收光谱检测了此化合物分子内光诱导电子转移所形成的电荷分离态 .在溶液中激发 FL,电子可从 FL有效地转移到 AQ,其速率常数为 3 .95× 1 0 9s-1,效率为 95 % .但由于电荷分离态寿命较短 ,瞬态吸收信号弱 ,若在此溶液中加入二氧化钛 (Ti O2 )纳米胶体 ,使 FL-AQ吸附在胶体上 ,电荷分离态信号明显增强 .4 80 nm处 FL+·的寿命为1 1 .1μs;5 60 nm处 AQ-·的寿命为 8.

The diad composed of fluorescein and 2-methyl-anthraquinone(FL-AQ) has been synthesized and its photophysical properties have been examined by absorption, fluorescence spectroscopy and fluorescence lifetime. The charge-separated state formed by photo-induced intramolecular electron transfer has been detected by nanosecond transient absorption spectroscopy for the first time. When FL is excited in solution, the photo-induced electron transter from FL to AQ proceeds efficiently. The rate constant and the efficiency of intramolecular electron transfer are 3.95×10 9 s -1 and 95% respectively. Its charge-separated state lifetime is too short to detect obviously by transient absorption spectroscopy. Adding of nanometer-size TiO_2 colloids to FL-AQ ethanol solution can prolong the lifetime of charge-separated state, so its transient absorption signal is recorded significantly. The decay lifetime of FL +· at 480 nm is 11.1 μs. The decay lifetime of AQ -· at 560 nm is 8.93 μs.