Design and application of tri-benzimidazolyl star-shape molecules as fluorescent chemosensors for the fast-response detection of fluoride ion

Abstract

Three tri-benzimidazolyl star-shape molecules have been successfully designed and applied as new fluorescent chemosensors for the detection of fluoride ion for the first time. They are easily obtained by the simple condensation of o-phenylenediamines and trimesic acid in the presence of polyphosphoric acid as catalyst. Three chemosensors show good selectivity, high sensitivity, and fast response toward F−. The addition of fluoride ion to the chemosensors causes a dramatically observable colour change from blue to light cyan not only in solution, but also in solid state under UV light. 1H NMR and DFT calculations studies confirm that the F− ion facilitates its recognition due to the formation of NH⋯F hydrogen bond and subsequent deprotonation as designed. In addition, chemosensors 3 can be reversible and reusable for sensing fluoride ion, resulting that they can be developed as an IMPLICATION type logic gate at molecular level. Moreover, these chemosensors have also been successfully applied to the detection of fluoride ion from inorganic origin and commercial toothpaste sample.