Amplified excited state intramolecular proton transfer fluorescence of butterfly-shaped bis-2,6-dibenzothiazolylphenol

作者：Xuan Zhang, Wei-Wei Ma · 发表于：Methods and Applications in Fluorescence · 年份：2017 · DOI：10.1088/2050-6120/aa73b2 · 被引用次数：9 · 研究领域：Photochemistry and Electron Transfer Studies、Radical Photochemical Reactions、Luminescence and Fluorescent Materials

Abstract A butterfly-shaped benzothiazole derivative, bis-2,6-dibenzothiazolylphenol ( 2 ), was synthesized via 4-methylene bridging two 2,6-dibenzothiazolylphenol ( 1 ) molecules, and the excited-state intramolecular proton transfer (ESIPT) fluorescence of 1 and 2 were comparably investigated by steady-state spectroscopic experiments with the aid of theoretical simulations for structure and energy. It was found that 2 showed similar ESIPT emissions to those of 1 in solution and solid states, but the ESIPT fluorescence quantum yield was substantially amplified in the case of the more ‘integrated’ 2 . In both tetrahydrofuran (THF) and CHCl 3 solvents, ESIPT occurred and orange emissions at 580–590 nm from keto tautomers were observed, where the absolute fluorescence quantum yield was measured to be 0.28 and 0.41 for 1 , as well as 0.41 and 0.59 for 2 , respectively. In the solid state, 2 showed an ESIPT emission at 570 nm with an absolute fluorescence quantum yield of 0.38, which is substantially shorter and larger than the corresponding values of 1 (592 nm and 0.26) respectively. Furthermore, both 2 and 1 showed strongly blue-shifted green emissions around 520 nm from the deprotonated anion species in N,N-dimethyl formamide (DMF). A similar blue-shifted green emission was also found with the addition of fluoride in the THF solution of 2 or 1 , suggesting that the competitive deprotonation makes the ESIPT impossible.