Fluoride Anion Recognition by a Multifunctional Urea Derivative: An Experimental and Theoretical Study.

In this work we demonstrate the ability of a multifaceted N,N'-disubstituted urea to selectively recognize fluoride anion (F(-)) among other halides. This additional function is now added to its already reported organocatalytic and organogelator properties. The signaling mechanism relies on the formation of a charge-transfer (CT) complex between the urea-based sensor and F¯ in the ground state with a high association constant as demonstrated by absorption and fluorescence spectroscopy. The nature of the hydrogen bonding interaction between the sensor and F¯ was established by ¹H-NMR studies and theoretical calculations. Moreover, the recovery of the sensor was achieved by addition of methanol.