College of Chemistry, Chemical Engineering & Biotechnology, and Key Laboratory of Science & Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620, People's Republic of China.
Methods Appl Fluoresc. 2017 Jun 8;5(2):024013. doi: 10.1088/2050-6120/aa73b2.
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 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.
一种蝶形苯并噻唑衍生物，双（2,6-二苯并噻唑基）苯酚（2），通过 4-亚甲基桥将两个 2,6-二苯并噻唑基苯酚（1）分子连接起来合成，通过稳态光谱实验和理论模拟研究了 1 和 2 的激发态分子内质子转移（ESIPT）荧光，以研究结构和能量。结果发现，2 在溶液和固态中表现出与 1 相似的 ESIPT 发射，但在更“集成”的 2 的情况下，ESIPT 荧光量子产率大大增强。在四氢呋喃（THF）和 CHCl 溶剂中，观察到来自酮互变异构体的 580-590nm 的 ESIPT 橙色发射，其中 1 的绝对荧光量子产率分别为 0.28 和 0.41，2 的绝对荧光量子产率分别为 0.41 和 0.59。在固态中，2 表现出 570nm 的 ESIPT 发射，其绝对荧光量子产率为 0.38，这分别比 1 的相应值（592nm 和 0.26）短得多且大得多。此外，2 和 1 在 N,N-二甲基甲酰胺（DMF）中均显示出强烈的蓝移绿光发射，其来自去质子化的阴离子物种，在 2 或 1 的 THF 溶液中加入氟化物也发现了类似的蓝移绿光发射，这表明竞争去质子化使 ESIPT 不可能发生。
