Selective and pH‐Independent Detection of Ba<sup>2+</sup> in Water by a Benzo‐21‐crown‐7‐Functionalized BODIPY
Tobias Sprenger, Thomas Schwarze, Holger Müller, Eric Sperlich, Hans‐Jürgen Holdt, Marc Nazaré, Axel Hentsch, Sascha Eidner, Ronja Kraft, Michael U. Kumke
Abstract
Abstract Herein, we report on highly Ba 2+ selective fluorescence sensing in water by a fluorescent probe consisting of a benzo‐21‐crown‐7 as a Ba 2+ binding unit (ionophore) and a tetramethylated BODIPY fluorophore as a fluorescence reporter. This fluorescent probe showed a Ba 2+ induced fluorescence enhancement (FE) by a factor of 12±1 independently of the pH value and a high Ba 2+ sensitivity with a limit of detection (LOD) of (17.2±0.3) μM. Moreover, a second fluorescent probe consisting of the same BODIPY fluorophore, but a benzo‐18‐crown‐6 as a cation‐responsive binding moiety, showed an even higher FE upon Ba 2+ complexation by a factor of 85±3 and a lower LOD of (13±3) μM albeit a lower Ba 2+ selectivity. The fluorescence sensing mechanism of Ba 2+ was further investigated by time‐resolved fluorescence as well as transient absorption spectroscopy (TAS) and it turned out that within these probes a blocking of a photoinduced electron transfer (PET) by Ba 2+ is very likely responsible for the FE.