Rational construction of long-wavelength emissive AIE molecules and their application for sensitive and visual detection of HClO

Herein, two small-molecule fluorescent dyes, 2-(4-(diethylamino)-2-((4-(4,4,5,5- tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)benzylidene)malononitrile (BASM) and ethyl-2-cyano-3-(4-(diethylamino)-2-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)phenyl)acrylate (BASE) with aggregation-induced emission characteristics are facilely synthesized and they were applied for the sensitive and selective detection of hypochlorous acid (HClO). For these novel AIE molecules, intricate structure and enormous π-conjugation system are no longer necessary. Due to the enhanced effect of intramolecular charge transfer and restricted intramolecular rotation, BASM and BASE displayed reinforced and long-wavelength emission in solid states and aggregated states. Moreover, the BASM has been rationally designed as a fluorescent probe of HClO based on the selective reaction between the BASM and HClO which generates a fluorescence efficient cyano iminocoumarin. The BASM displays a wide linear range for HClO from 0.5 to 10 μM and the limit of detection is as low as 6.46 nM. Intriguingly, excess amount (10–50 μM) of HClO causes fluorescence quenching due to a unique oxidation process, also explains the sensitivity and selectivity of BASM towards HClO. Furthermore, probe BASM is successfully employed for several practical applications such as detection of HClO in actual samples, fabrication of paper-based sensors, and fluorescence imaging in living bacteria.