An unique furan/thiophene substituted β-diketonate derivatives bearing triphenylamine with dual-state emission

Traditional β-diketones are rarely used as fluorescent emitters. Here, two novel triphenylamine-modified β-diketonate derivatives containing either a furan or thiophene unit (TPA-DK-O and TPA-DK-S) have been designed, synthesized and fully characterized. Both of the emitters have D-A type configuration, and show abnormal dual-state emissive characters with high quantum efficiency both in dissolved and aggregate state owning to rational design strategy. Additionally, owing to their molecular conformational flexibility and inherent intramolecular charge transfer characteristics, TPA-DK-O and TPA-DK-S show intriguing optical features such as solvatochromism, vicosity-dependent fluorescence and temperature response characteristics. The solvatochromism is derived from the intramolecular charge transfer effect which is confirmed by density functional theory calculation and fluorescence in solvents of different polarities. These unique optical properties of TPA-DK-O and TPA-DK-S are expected to be utilized for detecting local viscosity, polarity of system and temperature sensing. Moreover, the excellent dual-state emissive characters of TPA-DK-O are utilized for chemical sensors and cell imaging. The metal ion detection experiments indicated that TPA-DK-O has a fluorescence response capability to Fe3+ and Mg2+, and has a good linear relationship in the concentration range of 48–800 μM and 0–30 μM for Fe3+ and Mg2+, respectively. The cell incubation experiments shows that TPA-DK-O has low toxicity and good biocompatibility for cells. The cell imaging experiments reveals that TPA-DK-O not only stains and images cells, but also responds to Fe3+ in living cells. Making a contrast between TPA-DK-O and TPA-DK-S, it is found that replacing furan with thiophene in the β-diketonate derivatives showed slight effects on optical properties.