A chemosensor with a paddle structure based on a BODIPY chromophore for sequential recognition of Cu2+ and HSO3−

In this study, a highly selective chemosensor ML based on a BODIPY fluorescent chromophore was synthesized for sequential recognition of Cu2+ and HSO3− in a CH3OH/H2O (99 : 1 v/v) system, which contained three recognition sites and its structure characterized by 1H NMR, 13C NMR and ESI-HR-MS. The sensor ML showed an obvious “on–off” fluorescence quenching response toward Cu2+ and the ML-Cu2+ complex showed an “off–on” fluorescence enhancement response toward HSO3−. The detection limit of the sensor ML was 0.36 μM to Cu2+ and 1.4 μM to HSO3−. In addition, the sensor ML showed a 1 : 3 binding stoichiometry to Cu2+ and the recovery rate of ML-Cu2+ complex identifying HSO3− could be over 70%. Sensor ML showed remarkable detection ability in a pH range of 4–8.