Di-(2-picolyl)-N-(2-quinolinylmethyl)amine-Functionalized Triarylboron: Lewis Acidity Enhancement and Fluorogenic Discrimination Between Fluoride and Cyanide in Aqueous Solution.

Triarylboron-based Lewis acids as fluoride sensors face a stimulating academic challenge because of the high hydration enthalpy of fluoride, and are usually influenced by a competing response for cyanide ion. Herein, we present a new triarylborane functionalized by a metal-ion ligand, di-(2-picolyl)-N-(2-quinolinylmethyl)amine, with subsequent metalation. In aqueous solution, this triarylborane (QB) can capture fluoride and cyanide anions through chelation induced by the synergy of boron and metal ions. Moreover, this triarylborane moiety acts as a fluorescent reporter of the binding, allowing for discrimination between fluoride and cyanide anions through dual-channel fluorescence changes. The different chelation models and fluorogenic responses of this sensor toward F- and CN- were verified by the single-crystal structures of 2-to-2 adduct for KCN and 1-to-1 for KF.