A cationic triarylborane as water-tolerant fluorescent chemosensor for fluoride anions

A new cationic triarylborane has been synthesized by methylation of a dimethylamino electron donor group in a neutral donor-π-acceptor type system, which also includes a dimesitylboryl group as electron acceptor. Its single- and two-photon excited fluorescence emission properties have been examined, and it has been found to be a highly fluorescent chemosensor for fluoride anions in THF solutions. This cation exhibits a higher sensitivity for fluoride anions compared to its neutral precursor, which is attributed to the increased Lewis acidity of the boron center, as well as its enhanced Coulombic attraction for anions. It has also been demonstrated to be water-tolerant.