Photophysical and cyanide recognition properties of a pyridinium inner salt compound

Abstract A pyridine inner salt compound 2-{2-[7-( N, N -diethylamino)coumarin]vinyl}- N -(3-sulfonatepropyl)-pyridinium, inner salt ( 1 ) with strong red fluorescence emission and good water solubility was synthesized by condensation reaction between 7-diethylaminocoumarin-3-aldehyde and 2-methyl- N -(3-sulfooxypropyl)pyridinium, inner salt. Investigation on UV–vis absorption, fluorescence properties and cyanide recognition of the compound indicates that this compound can specifically recognize cyanide in aqueous solution with detection limit being 0.0003 μM. The color of compound solution exhibits change from brick red to purple accompanied by red fluorescence decrease, which can realize naked eye observation. Based on in situ 1 H NMR, mass spectra and Job’s plot, 4-coumarin is more likely to react with cyanide anions by nucleophilic substitution.