Design and preparation of organic small molecules in NIR-II and their application in fluorescence imaging/photothermal therapy/ photoacoustic imaging

Recently, organic small molecule probes with good development potential have attracted extensive attention from researchers due to their advantages such as controllable structure, good biocompatibility, fast excretion rate and no long-term toxicity. Among various types of organic small molecule probes, it is worth mentioning that the emergence of fluorescent probes with donor-acceptor-donor (D-A-D) structure plays an important role. Thanks to this, recently, many studies have focused on further modification of the molecular skeleton of D-A-D structure in order to further improve the fluorescence performance. In view of the fact that the synthesis of organic fluorescent small molecules with S-D-A-D-S structure by introducing a shielding unit proved to be effective in obtaining fluorescent molecules with increased quantum yield, an organic fluorescent molecule with D-A-D structure is designed in this paper, and an organic fluorescent molecule with S-D-A-D-S structure is synthesized on the basis of the original structure by introducing a shielding unit, which is used in fluorescence imaging, photothermal therapy and photoacoustic imaging.