A novel off-on fluorescent chemosensor for Al 3+ derived from a 4,5-diazafluorene Schiff base derivative.

The performance of a chemosensor is closely related to its structure. A new Schiff bass (DFSB) based on 4,5-diazafluorene units has been synthesized in this work. The interaction of DFSB with different metal ions has been studied using UV-vis absorption spectra and fluorescent spectra. The results show that DFSB is a highly selective and sensitive probe for Al 3+ ions over other commonly coexisting metal ions in ethanol. A very obvious fluorescence enhancement effect was observed, and a turn-on ratio over 1312-fold was triggered with the addition of 10 equiv. of Al 3+ ions. What is more, such fluorescent responses could be detected by the naked eye under a UV-lamp. The lowest detection limit for Al 3+ was determined as 3.7 × 10 -8 M. The complex solution (DFSB-Al 3+ ) exhibited reversibility with EDTA. These results may be caused by the unique molecular structure.