An Intramolecular Charge Transfer Induced Fluorescent Chemosensor for Selective Detection of Mercury (II) and its Self‐Turn‐On Inside Live Cells at Physiological pH

Abstract

AbstractA new turn‐on fluorescence small‐molecular dicarboxylic acid functionalized chemosensor (L2) has been designed strategically. The bidentate ligand (L2) is exceedingly selective for the sensing of HgII ions over other heavy‐metal ions, and exhibits excellent resolution on imaging living cells in‐vitro. The HgII binding mechanism by the probe occurs selectively through lone pair of electrons from imine nitrogens, which was established by using 1H NMR titrations, density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT). The free acid protons facilitated enhanced fluorescence intensity upon shift at deprotonation and gave a 50 nm hypsochromic at slight basic medium. The para‐ and meta‐positions of imine nitrogen atoms with respect to the donor (NH2) inducing the intramolecular charge transfer (ICT). The designed probe has high sensitivity to mercury(II) ions, excellent cell membrane permeability and negligible cytotoxicity, which result in bright and specific detection of HgII in living cells (HeLa cells) by fluorescence turn‐on at physiological pH. Further, the strategic approach executed in this work would be useful to design new chemosensors for sensing of different molecules or ions in future.