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.