近紅外光響應之聚集誘導發光分子之設計、合成與性質

Abstract

近紅外光區 (NIR, 700–1700 nm) 螢光染料因具備優異的組織穿透能力與低背景干擾，於生物影像應用中展現高度潛力。然而，傳統近紅外染料常因聚集誘導螢光淬滅效應與在生理環境中偏低的量子產率而受限其應用。為突破此一瓶頸，本研究設計並合成一系列具備電子予體–受體 (donor–acceptor, D-A) 結構的小分子螢光染料- BBT-D1、TTD-D1 與 TTD-D2。透過引入萘環與苯甲醚作為分子內轉子 (motor) 以有效抑制分子聚集時的 π−π 堆疊與分子內運動，進而促發聚集誘導發光 (aggregation-induced emission, AIE) 特性。此外，我們藉由調控電子受體核心的電性 (BBT 與 TTD 核心)，並在 - 橋接單元上導入不同取代基碳鏈以提升電子予體端的立體障礙，進一步調控分子內電荷轉移與骨架扭曲，有效調控其光物理性質。在包覆成奈米粒子後，BBT-D1 與 TTD-D1 分別表現出波長為 1209 nm 與 1009 nm的 NIR-II 區發光，並具有明顯的 AIE 效應；TTD-D2 亦進入 NIRII 波段，且於聚集狀態下展現更顯著之 AIE 行為。整體而言，本研究透過電子效應、骨架剛性與立體障礙等多重分子設計策略，成功開發具備高螢光效率與 NIRII 發光能力之小分子 AIE 材料，未來有望應用於高靈敏度與深層組織穿透之生物影像技術。

Fluorescent dyes that emit in the near-infrared (NIR, 700–1700 nm) spectrum offer advantages such as deep tissue penetration and minimal background autofluorescence, making them highly promising for biomedical imaging. Nevertheless, conventional NIR dyes frequently encounter aggregation-caused quenching (ACQ) and exhibit poor quantum yields under physiological environments, thereby restricting their practical application. To address these limitations, a series of small-molecule fluorescent dyes incorporating donor–acceptor (D–A) architectures — BBT-D1, TTD-D1, and TTD-D2 were rationally designed and synthesized. By incorporating naphthalene and methoxybenzene as intramolecular motors, we effectively suppressed π–π stacking and intramolecular motions when aggregated, thereby promoting aggregation-induced emission (AIE) characteristics. Furthermore, we modulated the electronic properties of the acceptor core (BBT and TTD). We introduced various alkyl chains on the -bridging unit to enhance steric hindrance at the donor end. This strategy allowed us to fine-tune intramolecular charge transfer (ICT) and backbone distortion, thereby tailoring the photophysical properties of the dyes. Upon nanoparticle encapsulation, BBT-D1 and TTD-D1 exhibited NIR-II fluorescence peaks at 1209 nm and 1009 nm, respectively, along with pronounced AIE behavior; TTD-D2 also emitted in the NIR-II region and showed even stronger AIE effects in the aggregated state. Overall, this study demonstrates that a molecular design strategy involving electronic modulation, backbone rigidity, and steric engineering enables the development of high-efficiency, NIR-II emissive AIEactive dyes with promising potential for high-sensitivity, deep-tissue bioimaging applications.