White Emitters by Tuning the Excited-State Intramolecular Proton-Transfer Fluorescence Emission in 2-(2′-Hydroxybenzofuran)benzoxazole Dyes
White Emitters by Tuning the Excited-State Intramolecular Proton-Transfer Fluorescence Emission in 2-(2′-Hydroxybenzofuran)benzoxazole Dyes
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DOI：
10.1002/chem.201402717
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发表时间：
2014-09-26
影响因子：
4.3
通讯作者：
Ziessel, Raymond
中科院分区：
文献类型：
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作者：
Benelhadj, Karima;Muzuzu, Wenziz;Ziessel, Raymond
报道了一系列新的基于2-（2 ′-羟基苯并呋喃）苯并恶唑（HBBO）的染料的合成、结构和物理性质。在光激发时，这些染料表现出强烈的双重荧光，其贡献来自烯醇（E*）和酮（K*）发射，其中K* 通过激发态分子内质子转移（ESIPT）形成。我们发现，发射强度的比例E*/K* 可以微调明智的装饰分子的核心与供电子或吸引取代基。由强供体（nNBu（2））和强受体基团（分别为CF 3和CN）官能化的推拉染料9和10表现出强烈的双发射，特别是在非极性溶剂如环己烷中，其中两个谱带的最大波长更强烈地分离。此外，所有的染料表现出强大的固态双发射在溴化钾矩阵和聚合物薄膜增强量子产率达到54%。一个明智的选择的取代基导致白色发射在溶液中和固体状态。最后，这些实验结果进行了分析，通过含时密度泛函理论（TD-DFT）计算，这证实，一方面，只有E* 和K* 发射存在（没有旋转异构体），另一方面，在激发态的两个互变异构体的相对自由能指导E*/K* 发射强度的比例。
The synthesis, structural, and photophysical properties of a new series of original dyes based on 2-(2'-hydroxybenzofuran) benzoxazole (HBBO) is reported. Upon photoexcitation, these dyes exhibit intense dual fluorescence with contribution from the enol (E*) and the keto (K*) emission, with K* being formed through excited-state intramolecular proton transfer (ESIPT). We show that the ratio of emission intensity E*/K* can be fine-tuned by judiciously decorating the molecular core with electron-donating or -attracting substituents. Push-pull dyes 9 and 10 functionalized by a strong donor (nNBu(2)) and a strong acceptor group (CF3 and CN, respectively) exhibit intense dual emission, particularly in apolar solvents such as cyclohexane in which the maximum wavelength of the two bands is the more strongly separated. Moreover, all dyes exhibit strong solid-state dual emission in a KBr matrix and polymer films with enhanced quantum yields reaching up to 54%. A wise selection of substituents led to white emission both in solution and in the solid state. Finally, these experimental results were analyzed by time-dependent density functional theory (TD-DFT) calculations, which confirm that, on the one hand, only E* and K* emission are present (no rotamer) and, on the other hand, the relative free energies of the two tautomers in the excited state guide the ratio of the E*/K* emission intensities.