Triarylborane-Appended New Triad and Tetrad: Chromogenic and Fluorogenic Anion Recognition

Facile synthesis of triad 3 and tetrad 4 incorporating −B­(Mes)2 (Mes = mesityl (2,4,6-trimethylphenyl)), boron dipyrromethene (BODIPY),
and triphenylamine is reported. Introduction of two dissimilar acceptors
(triarylborane and BODIPY) on a single donor resulted in two distinct
intramolecular charge transfer processes (amine-to-borane and amine-to-BODIPY).
The absorption and emission properties of the new triad and tetrad
are highly dependent on individual building units. The nature of electronic
communication among the individual fluorophore units has been comprehensively
investigated and compared with building units. Compounds 3 and 4 showed chromogenic and fluorogenic responses
for small anions such as fluoride and cyanide.