A new fluorescent-colorimetric chemosensor for fluoride anion based on benzimidazolium salt

Two new benzimidazolium salts with the same cationic moiety and different anions 3-(2'-((8 ''-hydroxy-9 '',10 ''-dioxo-9 '',10 ''-dihydroanthracen-1 ''-yl)oxy)ethyl)-1-(pyridin-2-ylmethyl)-1H-benzo[d]imidazol-3-ium bromide and 3-(2'-((8 ''-hydroxy-9 '',10 ''-dioxo-9 '',10 ''-dihydroanthracen-1-yl)oxy)ethyl)-1-(pyridin-2-ylmethyl)-1H-benzo[d]imidazol-3-ium hexafluorophosphate were prepared and characterized. The single crystal structure of 3-(2'-((8 ''-hydroxy-9 '',10 ''-dioxo-9 '',10 ''-dihydroanthracen-1 ''-yl)oxy)ethyl)-1-(pyridin-2-ylmethyl)-1H-benzo[d]imidazol-3-ium bromide was determined by X-ray single crystal diffraction. Particularly, anion recognition using 3-(2'-((8 ''-hydroxy-9 '',10 ''-dioxo-9 '',10 ''-dihydroanthracen-1 ''-yl)oxy)ethyl)-1-(pyridin-2-ylmethyl)-1H-benzo[d]imidazol-3-ium hexafluorophosphate as a chemosensor was carried out via fluorescence and ultraviolet spectroscopy, H-1 NMR titrations, HRMS and IR spectra. The response of this chemosensor to fluoride anion can be observed through both remarkable fluorescence quenching and color change under visible light (from orange to purple). The results indicated that this chemosensor can distinguish fluoride anion from other anions via the instrument and naked eyes, and this is greatly convenient in practical operation. (C) 2018 Elsevier Ltd. All rights reserved.