ESIPT based Hg2+ and fluoride chemosensor for sensitive and selective ‘turn on’ red signal and cell imaging

Abstract

An excited state intramolecular proton transfer (ESIPT) enabled fluorescent sensor phenanthroline diimino phenol (PDP) for Hg²⁺ has been designed and synthesized. PDP acts as a dual sensor and selectively detects only Hg²⁺ in mixed aqueous medium and fluoride in acetonitrile medium over other competing metal ions and anions. The binding of PDP with Hg²⁺ is supported by DFT. The ESIPT phenomenon in PDP is favored in the presence of Hg²⁺, which is rarely reported, along with an intense red fluorescence suppressing other competing metal ions. Among different anionic analytes, only fluoride shows a visually detectable exciting color change from pale yellow to pink with almost similar emission characteristics. PDP also demonstrates its importance in the fluorescent imaging of Hg²⁺ ions in human cancer cells.