Tasaki Satomi, Momotake Atsuya, Kanna Yoko, Sato Tomoo, Nishimura Yoshinobu, Arai Tatsuo
Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Photochem Photobiol Sci. 2015 Oct;14(10):1864-71. doi: 10.1039/c5pp00088b.
We report herein the selective preparation of normal, tautomeric, and dual-fluorescent molecules with a common ESIPT core. 2'-Hydroxyacetophenone (OHAP) is known as a typical molecule that undergoes excited-state intramolecular hydrogen transfer (ESIPT) to display fluorescence emission from the excited state of the tautomer. In this study, a series of ten OHAP-cored fluorescent molecules were prepared and their excited state properties have been explored. The bathochromic shift of the π-π* absorption band with π-extensions of substituents of these molecules indicates that the excitation energy of the normal form of the OHAP unit was reduced due to the substituents, while the energy of the excited tautomer appeared to be independent of the π-extension of the substituents. When pyrene or anthracene was connected at the end (molecules 4 and 5), only normal fluorescence appeared, and the tautomer fluorescence disappeared. An anthracene derivative (molecule 10) displayed dual fluorescence, indicating that the normal and the tautomer excited states were energetically "balanced". A fluorescence lifetime analysis revealed the ESIPT reaction rate of 10 to be much slower than those of other derivatives and that the normal and tautomer forms were in equilibrium in the excited state.
我们在此报告了具有共同激发态分子内质子转移（ESIPT）核心的正常、互变异构和双荧光分子的选择性制备。2'-羟基苯乙酮（OHAP）是一种典型的分子，它会发生激发态分子内质子转移（ESIPT），从互变异构体的激发态发出荧光。在本研究中，制备了一系列十个以OHAP为核心的荧光分子，并对它们的激发态性质进行了探索。这些分子的取代基发生π-扩展时，其π-π*吸收带发生红移，这表明由于取代基的作用，OHAP单元正常形式的激发能降低，而激发互变异构体的能量似乎与取代基的π-扩展无关。当芘或蒽连接在末端时（分子4和5），只出现正常荧光，互变异构体荧光消失。一种蒽衍生物（分子10）显示出双荧光，表明正常和互变异构激发态在能量上“平衡”。荧光寿命分析表明，10的ESIPT反应速率比其他衍生物慢得多，并且正常和互变异构形式在激发态处于平衡状态。
