Fluorinated tolane-based fluorophores bearing a branched flexible unit with aggregation-induced emission enhancement characteristics
Fluorinated tolane-based fluorophores bearing a branched flexible unit with aggregation-induced emission enhancement characteristics
复制标题
基于氟化甲苯烷的荧光团带有支链柔性单元，具有聚集诱导的发射增强特性
DOI：
10.1039/d1nj05822c
复制
发表时间：
2022
影响因子：
3.3
通讯作者：
Konno Tsutomu
中科院分区：
文献类型：
--
作者：
Yamada Shigeyuki;Sato Masaya;Uto Eiji;Kataoka Mitsuki;Morita Masato;Konno Tsutomu
像甲苯这样的小荧光分子有利于广泛的应用，例如在发光传感器和有机发光器件中的应用。然而，甲苯烷衍生物在溶液中不发出荧光，因为它们会立即从 ππ* 内部转换为具有反式弯曲结构形状的暗 πσ* 激发态。我们专注于基于tolane的荧光分子的开发，发现将氟原子引入到tolane的一个芳环中，由于电子密度分布和分子间氢键形成的刚性分子聚集结构，有助于荧光发射。然后，我们专注于分子调制，特别是引入支化结构，不影响电子密度分布的柔性单元；这可以增加两个tolanes之间的界面距离，以通过能量转移抑制非辐射过程。氟化甲苯在稀溶液中发光，光致发光（PL）效率相对较弱，而环状柔性单元（例如四氢呋喃环）是柔性单元在晶态下表现出强光致发光的最佳结构，并且具有高光致发光效率。此外，发现带有环状柔性单元的基于氟化甲苯烷的荧光团表现出聚集诱导的发射增强特性。这项研究的结果提供了一种新颖的分子设计策略来开发基于甲苯烷的强固态发光体。
Small fluorescent molecules like tolanes are advantageous for broad applications, such as those in luminescence sensors and organic light-emitting devices. However, tolane derivatives are non-fluorescent in solution because of their immediate internal conversion from ππ* to dark πσ* excited states with a trans-bend structural shape. We focused on the development of tolane-based fluorescent molecules and found that the incorporation of fluorine atoms into one aromatic ring of tolane contributed to the emission of fluorescence owing to the electron density distribution and rigid molecular aggregated structure formed by intermolecular hydrogen bonding. Then, we focused on the molecular modulation, particularly the introduction of a branched structure, of a flexible unit that does not influence the electron density distribution; this could increase the interfacial distance between two tolanes to suppress non-radiative processes through energy transfer. Fluorinated tolanes were found to luminesce in dilute solutions with a relatively weak photoluminescence (PL) efficiency, whereas it was revealed that a cyclic flexible unit, such as a tetrahydrofuran ring, was the optimal structure for the flexible unit to exhibit intense PL in the crystalline state with high PL efficiency. Additionally, fluorinated tolane-based fluorophores bearing a cyclic flexible unit were found to exhibit aggregation-induced emission enhancement characteristics. The findings of this study offer a novel molecular design strategy to develop intense solid-state tolane-based luminophores.