Facile and Highly Selective Ratiometric Fluorescence Probe Based on Benzo[5]helicene for the Detection of Hypochlorous Acid

In physiological processes, hypochlorous acid can regulate in vitro signaling molecules as one kind of reactive oxygen species (ROS). Serious diseases, such as cardiovascular disorders, neurodegenerative diseases, Alzheimer's disease, and cancers are usually concerned with the abnormal levels of hypochlorous acid in human bodies. Herein, we report a new probe DPH-BP for HClO, which consists of a benzo[5]helicene-pyridine fluorophore and benzyl-benzeneboronic acid pinacol ester as HClO reaction sites. The structural motifs combined with chromogenic media and fluorescence become a single-molecule sensor response in aqueous solutions. In the presence of HClO, this probe shows a remarkable blue shift of fluorescence from 536 to 452 nm in an aqueous solution and obvious fluorescence color change from yellow to blue. In the same conditions, almost no response can be recorded with the other common ROS/RNS, such as H2O2, TBHP, (OH)-O-center dot, t-BuO center dot, ONOO-, and O-2(center dot-). As we have designed, the oxidation of phenylboronic ester by HClO induces the cleavage of the benzyl in DPH-BP, which has been proven by H-1 NMR spectra and density functional theory calculations. To the best of our knowledge, this is the first report of the analysis of HClO using the oxidation of benzyl-benzeneboronic acid pinacol ester.