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

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-, H2PO4-, CN-, Cl-, CH3COO-, Br-, PhCOO-, HSO4-, and NO3- 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, 1H NMR, 19F 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.

Automated summary

In this study, fluorescent chemosensors with a benzoselenodiazole/benzothiadiazole unit were designed and synthesized. These chemosensors exhibited selectivity towards F- and showed a visible color change upon the addition of F-. The sensing mechanism was found to involve the deprotonation of the -NH proton of the benzimidazole group by F-. One of the chemosensors showed higher selectivity and sensitivity towards F- compared to the other.