Benzo‐Crown‐Ether Functionalized O‐BODIPY Probes for Cations – A Selective Fluorescent Probe for Ba 2

• Published in: Chemistry : a European journal 2024-08, Vol.30 (45)
• Main Authors: Sprenger, Tobias, Schwarze, Thomas, Holdt, Hans‐Jürgen, Hentsch, Axel, Nazaré, Marc
• Format: Article
• Language: English
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202401928

Herein, we report the synthesis and sensing characteristics of 4,4′‐methoxy‐substituted BODIPY fluorescent probes (O‐BODIPYs) 3 , 4 and 5 equipped with differently sized benzo‐crown ethers (cf. Scheme 1, 3 (benzo‐15‐crown‐5), 4 (benzo‐18‐crown‐6) and 5 (benzo‐21‐crown7)). O‐BODIPYs 3 , 4 and 5 exhibited in comparison to their known F‐BODIPY analogues 3a , 4a and 5a (cf. Scheme 1) an improved solubility in aqueous medium and higher fluorescence quantum yields. Fluorometric study in aqueous solutions of 3 , 4 and 5 in the presence of different cations show cation induced fluorescence enhancements (FE). Compared to the benzo‐crown ether substituted F‐BODIPY analogues 3a , 4a and 5a , we found for the free O‐BODIPYs 3 , 4 and 5 higher fluorescence quantum yields ( φ f ) but lower cation induced FEs. We show that in aqueous medium the fluorescence quenching process (OFF switching), a photoinduced electron transfer, in O‐BODIPYs 3 , 4 and 5 is less effective and consequently sensitive and selective ON switching of the fluorescence by cations, too. Albeit these observations the novel benzo‐21‐crown‐7 equipped fluorescent probe 5 exhibits a good fluorometric Ba 2+ selectivity and Ba 2+ sensitivity in conjunction to their aqueous solubility.