Wu Yingnan, Zhao Yanliang, Zhou Panwang, Zheng Daoyuan, Wang Honglei, Tang Shanliang, Tian Jiarui, Yang Songqiu, Deng Weiqiao, Han Keli, Song Fengling
Institute of Molecular Sciences and Engineering, Shandong University, Qingdao 266237, China.
State Key Laboratory of Fine Chemicals, Dalian University of Technology, No. 2 Linggong Road, High-tech District, Dalian 116024, China.
J Phys Chem Lett. 2020 Jul 16;11(14):5692-5698. doi: 10.1021/acs.jpclett.0c01297. Epub 2020 Jul 2.
It is a challenge to rationally design an organic molecule with thermally activated delayed fluorescence (TADF) due to the intrinsically spin-forbidden transition. Meanwhile, those reported TADF organic molecules have difficulty to be directly applied in the field of biological and medical imaging because they usually have no water solubility. Here, a water-soluble TADF organic molecule DCF-BXJ was developed by introducing a flexible propenyl group into the commercial traditional fluorophore DCF (2,7-dichlorofluorescein). The flexible group provides nonradiative rotational motion, which causes an efficient energy level cross between the S state and the T state of DCF-BXJ. Results of transient absorption spectra and theoretical calculations supported that nonradiative rotational motion of the flexible group can enhance intersystem crossing (ISC) and bring out TADF. This work provides a new mechanism explanation for TADF existing in organic molecules.
由于固有的自旋禁戒跃迁，合理设计具有热激活延迟荧光（TADF）的有机分子是一项挑战。同时，那些已报道的TADF有机分子难以直接应用于生物和医学成像领域，因为它们通常不具有水溶性。在此，通过将一个柔性丙烯基引入商业化的传统荧光团DCF（2,7-二氯荧光素），开发出了一种水溶性TADF有机分子DCF-BXJ。该柔性基团提供非辐射旋转运动，这导致DCF-BXJ的S态和T态之间发生有效的能级交叉。瞬态吸收光谱和理论计算结果支持，柔性基团的非辐射旋转运动能够增强系间窜越（ISC）并产生TADF。这项工作为有机分子中存在的TADF提供了一种新的机理解释。
