Selective Recognition of Fluoride by using a Benzobisimidazolium Derivative through Aggregation‐Induced Fluorescence

Abstract

A new benzobisimidazolium derivative (1) bearing four naphthalene moieties was synthesized and demonstrated as an F− ion‐selective fluorescent chemosensor. The fluorescence of 1 in acetonitrile (CH3CN) is significantly stronger with F− and acetate (CH3CO2 −), but not with other anions (Cl−, Br−, I−, HSO4 −, and H2PO4 −). The fluorescence of 1 is enhanced selectively with F− in the presence of a small amount of water. Our DFT calculations indicate that the electrostatic interactions between the positively charged benzobisimidazolium moieties and F− play an important role in the formation of stable aggregates. The formation of stable aggregates of 1 with F− in CH3CN is a key step for the selective sensing of F−, and the fluorescence of the aggregates is further enhanced in a mixture of 95 % CH3CN and 5 % water, which can be attributed to the aggregation‐induced emission.