Design, synthesis and applications of fluoride probe based on aromatization of isoquinolinium salts

A novel ratiometric fluorescent probe based on aromatization drive of isoquinolinium salts was designed, synthesized to recognize fluoride. The applications have shown that the probe has high selectivity and sensitivity to fluoride. Fluoride induces a cascade reaction of hydroxyl deprotection and 1,6-oxidative elimination, and causes a remarkable fluorescence enhancement. The relative fluorescent intensities (I-398/I-522) increased linearly with F- concentration in the range of 0-9.0 mu mol L-1. The limit of detection was very low (3.7 nM) due to the intrinsic aromatization drive of probe induced by F-. The recognition mechanism was demonstrated by mass spectrum (MS) and H-1 NMR. The in vitro imaging results showed that the new probe BIQS (2-[4-(tert-butyl-diphenyl-silanyloxy)-benzyl]-3-(4-methoxy- phenyl) -isoquinolinium nitrate) was membrane-permeable and could be applied into the determination of fluoride ions in living cells.