A NIR Molecular-level Framework Tracks Mercury Ions via Fast and Real-time Determination in Real Samples and Live Cells.

Bio-degradation of mercury ions and their abnormal bioaccumulation in the human body through the food chain can cause various diseases. Therefore, we have designed and synthesized a novel near-infrared (NIR) ratiometric fluorescent probe (E)-2-(3-(3-(1,3-dithiolan-2-yl)-4-hydroxystyryl)-5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (ICM-S-OH) for detecting Hg2+. Due to the Hg2+-promoted deprotection reaction of mercaptal, ICM-S-OH showed rapid response within 3 min, accompanied by a noticeable fluorescence change from yellow emission to red emission and colour change from yellow to pink. The fluorescence intensity ratio (F663/F593) has excellent linearity toward the concentration of Hg2+. The detection limit reaches 5.3 nM. Moreover, the sensing mechanism of ICM-S-OH towards Hg2+ supported by fluorescence, UV-vis, 1H NMR, HR-MS spectra and density functional theory (DFT) calculation. Moreover, Gibbs free energy change of the interaction process were calculated to study the thermodynamics. In particular, ICM-S-OH were further employed to detect Hg2+ in M.D. Anderson Metastatic Breast-231 cells (MDA-MB-231 cells) and seafood samples (shrimp and crab).