Na Weidan, An Lei, Wu Qiong, Cai Keying, Ou Changjin, Zhuang Wenchang
College of Chemistry and Chemical Engineering, Xuzhou University of Technology, Xuzhou, 221111, P. R. China.
School of Chemistry and Materials Science, Nanjing University of Information Science & Technology, Nanjing, 210044, P. R. China.
Chemistry. 2023 Nov 21;29(65):e202301997. doi: 10.1002/chem.202301997. Epub 2023 Oct 11.
Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.
电子接受单元在构建供体-受体（D-A）共轭有机光电材料中起着至关重要的作用；需要仔细揭示受体的电子结构和功能，以可控地调整光电性质。我们基于含砜或羰基的多环芳烃受体合成了两种具有相似分子骨架的D-A共轭有机荧光团TPA-SO和TPA-CO。TPA-SO和TPA-CO都表现出明显的溶剂极性依赖的光物理性质，并且由于强烈的分子内电荷转移过程，具有超过100 nm的大斯托克斯位移。实验证据表明，TPA-SO中的砜基团仅作为强吸电子单元。TPA-SO在溶液中呈现黄绿色发射，峰值为542 nm，绝对光致发光量子产率（PLQY）为98%，而TPA-CO中的羰基既可以作为吸电子单元，也可以作为自旋跃迁转换器，因此TPA-CO在溶液中呈现红色发射，绝对PLQY较低，为0.32%。令人印象深刻的是，从溶液态转变为聚集态时，TPA-SO纳米颗粒保持9.5%的高PLQY和适度的生物相容性，因此它们是用于细胞荧光成像的良好纳米试剂。结果表明，固有的受体特性在有机荧光团的光物理性质和应用中起着关键作用。
