Amide‐Triazolium‐Appended Anthracenes for Turn‐On Fluorescence Sensing of Anions in Noncompetitive and Competitive Solvents

A new anthracene-based receptor bearing two arms of amide-triazolium anion-binding sites, and its counterpart compound with one amide-triazolium arm, have been synthesized and characterized. Their ability to bind anions in different solvents (CH3 CN, CHCl3 and DMSO) has been investigated in detail by using fluorescence techniques. Both compounds exhibited significant fluorescence turn-on sensing of F- and H2 PO4- ions in noncompetitive and competitive environments with different binding modes. In CH3 CN and CHCl3 , the receptor with two triazoliums binds H2 PO4- in 1:1 and 1:2 host-guest complexes, showing anthracene-based excimer emission in the 1:1 complex, and strong monomer emission in the 1:2 complex. In DMSO, only the 1:1 stoichiometric complex was detected. In contrast, it binds with F- and AcO- with 1:2 stoichiometry both in noncompetitive and competitive solvents. The anion-binding mechanism of both compounds was also evaluated by 1 H NMR spectrometric titration and density functional theory calculation.