Exploiting aggregation induced emission and twisted intramolecular charge transfer in a BODIPY dye for selective sensing of fluoride in aqueous medium and living cells

A novel red fluorescent probe based on boron dipyrromethene (BODIPY) was successfully designed and synthesized, consisting of electron acceptor 1,3,5,7-tetramethyl-8-phenyl-BODIPY (BDP) and electron donor triphenylamine (WA) units using Suzuki cross-coupling methods TPA-BDP exploits the advantages of both aggregation-induced emission (AIE) and twisted intramolecular charge transfer (TICT). An X-ray crystal structure of TPA-BDP reveals a network of C-H center dot center dot center dot F intermolecular interactions which can contribute to rigidifying the molecular conformation. Thereby, aggregation restricts the intramolecular rotation associated with the donor moiety, inducing a great enhancement in the emission efficiency. This new dye features high sensitivity and excellent selectivity to fluoride ions with a detection limit of 0.73 mu M in aqueous medium. The sensing mechanism was systematically investigated by H-1 NMR, F-19 NMR, B-11 NMR and mass spectrometry. It is proposed that fluoride reacts in a nucleophilic displacement reaction at the BDP core which disrupts the structure of TPA-BDP, thereby causing the red fluorescence of TPA-BDP quenched. It is noteworthy that TPA-BDP has been utilized for the fluorescence imaging and fluoride ions detection in living cells with very low cytotoxicity. (C) 2018 Elsevier B.V. All rights reserved.