Pyrene-appended, benzimidazoliums-urea-based ratiometric fluorescent chemosensor for highly selective detecting of H₂PO₄ ^-

A novel flexible pyrene-based chemosensor 1 bearing two benzimidazolium moieties and a urea group was designed and synthesized. The binding properties of chemosensor 1 toward various anions were examined via UV-vis, fluorescence, and ¹H NMR spectroscopic methods. The results demonstrated that chemosensor 1 could distinguish H₂PO₄^- from other tested anions such as F^-, Cl^-, Br^-, I^-, AcO^- and HSO₄^- by ratiometric fluorescence as chemosensor 1 formed a complex with H₂PO ₄^- in 2-2 ratio via intermolecular excimer transduction in CH₃CN. The fluorescence response of chemosensor 1 to H ₂PO₄^- was hardly interfered by other anions. The detection limit of chemosensor 1 (5 × 10^-6 M) toward H ₂PO₄^- is 5.02 × 10^-7 M.