Acylhydrazone-derivated calix[3]carbazole: A chemodosimeter for the detection of both TBATB and Br₂

The detection of both Br₂ and its derivative of tetrabutylammonium tribromide (TBATB) is a very important issue concerning their biological toxicity but remains challenging. Fluorescent sensing is one of the few methods possessing both selectivity and sensitivity. Moreover, it could be able to be utilized in biological system, but rarely reported. In this paper, we synthesized an acylhydrazone-derivated calix[3]carbazole (Compd 2), which could not only serve as the fluorescent sensor for TBATB, with high selectivity over other tested halides, but also be used to monitor the process of TBATB's formation generated by mixing Br₂ and tetrabutylammonium bromide (TBAB). Furthermore, the 2/TBAB complex is able to detect Br₂ in solution, in solid state as well as within the cells. The mechanism study showed upon addition of TBATB, the ketal functional groups of 2 at its "bridge" were converted to be the keto, and thus emitting fluorescence. This chemodosimeter possessed excellent sensitity with the limits of detection (LOD) for Br₃^- and Br₂ are 104 nM and 458 nM, respectively. To the best of our knowledge, it is the first chemodosimeter for both Br₃^- and Br₂ on the basis of the mechanism of the ketal-to-keto conversion.