Ether based flexible bis Schiff base fluorescent colorimetric chemosensors for selective and sensitive detection of HF2- ion

Two simple and low cost bis Schiff base fluorescent colorimetric chemosensors L1 and L2 have been designed and synthesized. These sensors could detect important anion HF2- by change in both absorption and fluorescence intensity in methanol tris HCI buffer (1:1 v/v) solution at physiological pH. The mechanism of selectivity and sensitivity of these receptors to HF2- has proposed to be on the basis of photo-induced electron transfer (PET), chelation enhanced fluoresence (CHEF) and hydrogen bonding mechanism, confirmed by FT-IR, H-1-NMR and ESI-mass spectra. Interestingly, chelation of HF2- to the receptors takes place in 1:2 ratio, which has been confirmed by job plots analysis, ESI-mass spectra, DFT and TD-DFT studies. The detection limits of the probes L1 and L2 for HF2- were determined to be 6.1 mu M for L1 and 3.94 mu M for L2 respectively, on the basis of 3 sigma/K. Importantly, the low detection limits of L1 and L2 for HF2- suggest that L1 and L2 are sensitive sensors for detection of these ions in drinking water. The receptors L1 and L2 can successfully applied for detection and quantification of HF2- in real samples. To the best of our knowledge this is the third report of fluorescent colorimetric chemosensors for HF2- ions.