Multi-analyte, ratiometric and relay recognition of a 2,5-diphenyl-1,3,4-oxadiazole-based fluorescent sensor through modulating ESIPT

Abstract

A new two dipicolyl amine (DPA) dangled 2,5-diphenyl-1,3,4-oxadiazole derivatized sensor L has been designed and synthesized. Sensor L displays excited state intramolecular proton transfer (ESIPT) properties in buffered water solution (HEPES 10 mM, pH = 7.4). L shows highly selective and ratiometric fluorescence responses to Zn²⁺ in a 1 : 2 binding ratio. Fluorescence spectra and ¹H NMR studies demonstrate that L binds Zn²⁺ ions through its amide form, which promoted the ESIPT emission enhancement. The in situ generated L–2Zn²⁺ complex can serve as a relay recognition sensor toward PPi and S²⁻ via further complexation and Zn²⁺ sequestering processes respectively. Thus, multi-analyte and relay recognition of L through modulating ESIPT has been achieved.