Synthesis and anion binding properties of a urea-based molecular cleft

Abstract

A new urea-based molecular cleft (L) derived from propylene-linked dipodal amine has been synthesized and its binding affinities for anions have been investigated by H-1 NMR and UV-vis spectroscopic titrations in DMSO. The receptor has been shown to bind F-, HSO4-, H2PO4-, and AcO- in a 1:1 binding mode via hydrogen bonding interactions, providing the highest binding constant for F-. In addition, the new cleft shows a naked-eye color change in the presence of F- in DMSO. The interactions of L with fluoride have also been evaluated by theoretical calculations based on density functional theory (DFT), revealing that the cleft encapsulates a fluoride via four NH center dot center dot center dot F- and two CH center dot center dot center dot F- bonds.