A multi-stimuli responsive “AIE” active salicylaldehyde-based Schiff base for sensitive detection of fluoride

Abstract

In this work, (E)-2-[(pyridin-2-ylimino)methyl]phenol, a Schiff-base compound was synthesized and the investigation of solid state emission property was carried out. The observed bright emission in solid state was identified it as an ‘aggregation induced emission (AIE)’ active compound. The mechanism of AIE property was investigated and proposed to occur as J-aggregation mediated ‘excited state intramolecular proton transfer (ESIPT)’. It was interestingly observed that the compound exhibited mechanofluorochromic (MFC) property and changed its emission color from yellow to greenish-yellow after grinding. Furthermore, a very sensitive detection of F− was achieved with turn-on fluorescent emission with using the same compound. The detection limit was calculated and found to be 14.0 pM. The 1:1 binding of analyte with the fluorophore (host/guest) was supported with UV–vis and 1H NMR spectroscopes. Several important experimental findings were further supported theoretically by DFT and TD-DFT calculations.