Mo Chunshao, Yang Meijia, Cheng Zhixue, Tang Xikang, Yang Lifen, Su Ruonan, Li Jing, Feng Jiangshan, Fang Long, Yang Kexin, Chen Zhuanggui, Yu Dingshan
Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry, Sun Yat-sen University, Guangzhou, Guangdong Province, 510275, China.
Department of Pediatrics and Department of Allergy, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong Province, 510275, China.
Small. 2021 Sep;17(36):e2100955. doi: 10.1002/smll.202100955. Epub 2021 Jul 28.
Herein, alkoxylation chemistry is introduced as a "one-stone-three-birds" solution for exploring a new family of highly-fluorescent octupolar 2D-conjugated organic polymers/frameworks (OCOPs/OCOFs) combining far-red emission, high fluorescence quantum yield (QY), and strong two-photon absorption (TPA). Both alkoxy-substituted OCOP and OCOF comprising acrylonitrile-bridged strongly-coupled donor3-(acceptor core) chromophores densely packed in either disordered or ordered forms, exhibit significantly redshifted emission. They produce high QY of 22.2% and 27.8% in tetrahydrofuran, large TPA cross section of 600 and 1124 GM, and 2-3 folds and 15-30 folds that of non-alkoxylate amorphous counterpart respectively. Combined theoretical and experimental studies reveal unique "one-stone-three-birds" role of the alkoxylation in realizing red-shifted-emission, improved QY and TPA enabled by inducing steric hindrance effect for weakened π-π stacking, and triggering p-π conjugation effect for electronically engineering octupolar chromophores, while the crystalline engineering enables enforced coplanarity conformation and improved π-electron delocalization for further improved QY and TPA. The robust and biocompatible pentoxy-substituted polymer can be used not only as metal-free red-emissive phosphor for efficient warm white light-emitting diodes, but also as efficient two-photon fluorescence probes for bio-imaging.
在此，烷氧基化化学被引入作为一种“一石三鸟”的解决方案，用于探索一类新型的高荧光八极二维共轭有机聚合物/框架（OCOP/OCOF），该聚合物/框架结合了远红光发射、高荧光量子产率（QY）和强双光子吸收（TPA）。由丙烯腈桥连的强耦合供体3-（受体核心）发色团以无序或有序形式紧密堆积而成的烷氧基取代的OCOP和OCOF，其发射均出现显著红移。它们在四氢呋喃中的量子产率分别高达22.2%和27.8%，双光子吸收截面分别为600和1124 GM，分别是非烷氧基化无定形对应物的2 - 3倍和15 - 30倍。理论和实验相结合的研究揭示了烷氧基化在实现红移发射、提高量子产率和双光子吸收方面独特的“一石三鸟”作用，这是通过诱导空间位阻效应削弱π-π堆积，并触发p-π共轭效应来对八极发色团进行电子工程设计实现的，而晶体工程则实现了强制共平面构象并改善了π电子离域，从而进一步提高了量子产率和双光子吸收。这种坚固且具有生物相容性的戊氧基取代聚合物不仅可以用作无金属的红色发射磷光体用于高效暖白色发光二极管，还可以用作生物成像的高效双光子荧光探针。
