A hemicyanine-based dual-responsive fluorescent sensor for the detection of lithium and cyanide ions: application in living cells.

A hemicyanine-based colorimetric and fluorometric sensor, 2-(2-(2,3,5,6,8,9-hexahydrobenzo[b][1,4,7,10]tetraoxacyclododecin-12-yl)vinyl)-3,3-dimethyl-1-propyl-3H-indol-1-ium iodide (MH-5), was developed and synthesized to detect Li and CN ions in DMSO-PBS buffer solution (10 mM, pH 7.25, v/v 1:9). MH-5 displayed a rapid and highly selective colorimetric response to both Li and CN, indicated by a distinct color change from pink to pale pink in the presence of Li and to colorless upon CN detection, without interference from other cations or anions. The interaction mechanisms of MH-5 with Li and CN ions were investigated using various analytical techniques, including H NMR, ESI-MS, FT-IR spectroscopy, and Job's plot analysis. These studies suggest that CN is detected through nucleophilic addition to the indolium moiety of MH-5, while Li detection occurs via coordination with oxygen atoms in the crown ether structure. The fluorescence-based detection limits for Li and CN were determined to be 0.150 µM and 0.154 µM, respectively. Additionally, MH-5 was evaluated in living cells, demonstrating effective cell penetration and reliable detection of Li and CN ions for potential bio-imaging applications.