Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan.
Photochem Photobiol. 2020 Jan;96(1):21-27. doi: 10.1111/php.13165. Epub 2019 Oct 20.
We investigated the fluorescent properties, including the excited-state intermolecular proton transfer, of urea derivatives comprising a coumarin ring, which is a widely used fluorophore. We prepared two different coumarin-urea derivatives, 6CU and 7CU, which bear a urea-based substituent at the 6 and 7 positions of a coumarin ring, respectively. In the presence of the acetate ion, 7CU showed additional tautomer fluorescence emission with respect to 6CU, indicating that tautomer formation depends on the positions of the urea-based substituent on the coumarin ring. Thus, the resonance structures of urea derivatives might play an important role in the behavior of dual fluorescence, which is an important phenomenon applicable to photochemical anion sensing. Moreover, in order to further improve the fluorescence properties of the mentioned derivatives, a CF group was introduced in a phenyl ring opposite to a coumarin ring. The fluorescence quantum yield of 7CUCF thus synthesized was 65 times as large as that of 7CU, an observation that renders 7CUCF a suitable anion sensor candidate. The results of this study will contribute to the development of new molecular designs for highly fluorescent sensing.
我们研究了包含香豆素环的脲衍生物的荧光性质，包括激发态分子内质子转移。我们制备了两种不同的香豆素-脲衍生物，6CU 和 7CU，它们在香豆素环的 6 位和 7 位分别带有基于脲的取代基。在醋酸根离子存在下，7CU 相对于 6CU 显示出额外的互变异构荧光发射，表明互变异构形成取决于脲基取代基在香豆素环上的位置。因此，脲衍生物的共振结构可能在双荧光行为中起重要作用，双荧光是一种适用于光化学阴离子传感的重要现象。此外，为了进一步改善上述衍生物的荧光性质，在与香豆素环相对的苯基环上引入了 CF 基团。因此，合成的 7CUCF 的荧光量子产率是 7CU 的 65 倍，这一观察结果使得 7CUCF 成为合适的阴离子传感器候选物。本研究的结果将有助于开发用于高荧光传感的新型分子设计。
