Naphthyl-azine - aggregation induced emission, reversible acidochromism, cyanide sensing and its application in intracellular imaging

The naphthylhydrazone derivative 1-[(2-hydroxy-4,6-dimethoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol (H2L), an aggregation induced emission (AIE) active probe, has emerged as a promising solid-state emitter upon exercising restricted intramolecular rotation (RIR) in an ordered J-type self-assembly and accounts for solid-state sensitive fluorescence quenching of trifluoroacetic acid (HTFA) vapour with a limit of detection (LOD) of 1.41 ppm. A plausible mechanism of quenching may be the protonation driven destruction of compacted arrangement in the solid state of the probe. Interestingly, H2L exhibits reversible acidochromic behavior upon sequential addition of HTFA and TEA (triethylamine, NEt3) vapour, which has been utilized for information protection application using the "write-erase" technique. Moreover, the probe shows a selective and sensitive colorimetric and 'turn-on' fluorogenic response towards CN- amongst twenty anions, with a limit of detection (LOD) of 45.42 nM. The CN--sensing activity of H2L is also reversible in the presence of HTFA, and the probe can easily be recycled several times demonstrating its potent reusability and ardent support to sustainable development goals (SDGs). Furthermore, cytotoxicity studies reveal considerable biocompatibility and intracellular imaging of the probe, which reflects the AIEgenic properties and CN- detection in MDA-MB 231 cells as well.