Benzoselenadiazole containing donor–acceptor–donor receptor as a superior and selective probe for fluoride in DMSO

Benzoselenodiazole/benzothiadiazole containing donor–acceptor-donor (D-A-D) fluorescent chemosensor ( 1-Se and 1-S ) have been designed and synthesized which act as a significant chemosensor for ‘naked-eye’detection of F – in presence of all other interfering anions. The sensing mechanism via deprotonation of –NH proton of benzimidazole was established by UV–vis, FL, NMR and theoretical studies. 1-Se is more sensitive and selective over 1-S in terms of binding constant and detection limit. • New benzoselenodiazole and benzothiadiazole unit containing D-A-D receptors ( 1-Se and 1-S) are designed and synthesized. • A rapid colorimetric/fluorometric detection of fluoride (F – ) is established via the anion selective deprotonation of the probes. • Probe 1-Se is found to be a superior F – sensor over 1-S in terms of selectivity and sensitivity i.e. from binding constant and detection limit calculations. • The probe 1-Se forms a supramolecular aggregate through hydrogen bonding interactions which further decumulated upon the addition of F – in solution. Benzoselenodiazole/benzothiadiazole unit containing donor–acceptor-donor (D-A-D) fluorescent chemosensors ( 1-Se and 1-S ) have been designed, synthesized, and characterized by spectroscopic techniques viz NMR and Mass spectrometry. The addition of F – selectively induces a prominent ‘naked-eye’ color change for 1-Se from yellow to red and from light-green to reddish-orange for 1-S in DMSO. These probes also show selectivity towards F – in presence of other interfering anions, for instances, I – , H 2 PO 4 – , CN – , Cl – , CH 3 COO – , Br – , PhCOO – , HSO 4 – , and NO 3 – which is established by UV–Vis and FL spectroscopic studies. Furthermore, 1-Se is found to be more selective and sensitive towards F – over 1-S in terms of binding constant and detection limit. The sensing mechanism is found to occur through the deprotonation of the –NH proton of benzimidazole group by F – which is confirmed by various spectroscopic techniques, such as, 1 H NMR, 19 F spectroscopy, and DFT studies. The macroscopic studies, such as DLS, FEG-TEM, and DOSY NMR revealed that 1-Se forms aggregate in solution through hydrogen bonding interaction which decumulates upon the addition of F – in solution.