Fine Tuning of Multiphoton AIE Emission Behavior, Organelle Targeting, and Fluorescence Lifetime Imaging of Terpyridine Derivatives by Alkyl Chain Engineering
Shujing Wang, Ying Lin, Chengkai Zhang, Tong Zhu, Xiaohe Tian, Dandan Li, Wen Ma, Qiong Zhang, Jieying Wu, Yupeng Tian
Abstract
In this work, a series of multiphoton terpyridine agents (ZA, ZA-Mex, and ZA-Hex) for fluorescence lifetime imaging microscopy (FLIM) are designed and synthesized. The results from photophysical property research reveal that ZA-Hex, as an N-hexylated terpyridine salt, has stronger three-photon aggregation-induced emission (AIE) properties compared to ZA-Mex due to enhanced intramolecular charge transfer (ICT) performance. All three terpyridine derivatives possess suitable fluorescence intensities and stable fluorescence lifetimes under different pH conditions (pH = 4.0–8.0), thereby performing multiphoton fluorescence lifetime imaging. For biological imaging applications, it is found that ZA shows good lipid droplet (LD) turn-on fluorescence performance, and ZA-Hex could easily accumulate in mitochondria with high specificity. This is the first report of terpyridine salts as three-photon AIE probes used for multiphoton FLIM imaging.