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Ionization and Anion−π+ Interaction: A New Strategy for Structural Design of Aggregation-Induced Emission Luminogens

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posted on 30.10.2017, 00:00 by Jianguo Wang, Xinggui Gu, Pengfei Zhang, Xiaobo Huang, Xiaoyan Zheng, Ming Chen, Haitao Feng, Ryan T. K. Kwok, Jacky W. Y. Lam, Ben Zhong Tang
Recent years have witnessed the significant role of anion−π+ interactions in many areas, which potentially brings the opportunity for the development of aggregation-induced emission (AIE) systems. Here, a new strategy that utilized anion−π+ interactions to block detrimental π–π stacking was first proposed to develop inherent-charged AIE systems. Two AIE-active luminogens, namely, 1,2,3,4-tetraphenyloxazolium (TPO-P) and 2,3,5-triphenyloxazolium (TriPO-PN), were successfully synthesized. Comprehensive techniques such as single-crystal analysis, theoretical calculation, and conductivity measurement were used to illustrate the effects of anion−π+ interactions on the AIE feature. Their analogues tetraphenylfuran (TPF) and 2,4,5-triphenyloxazole (TriPO-C) without anion−π+ interactions suffered from the aggregation-caused emission quenching in the aggregate state, demonstrating the important role of anion−π+ interactions in suppressing π–π stacking. TriPO-PN was biocompatible and could specifically target lysosome in fluorescence turn-on and wash-free manners. This suggested that it was a promising contrast agent for bioimaging.