A Selective Colorimetric and Fluorescent Diphenylacetylene-Based Naphthalimide for Sensing of Cyanide

Abstract

A high selective fluorescent probe 4 for cyanides was developed based on the Sonogashira reaction between N-butyl-4-bromo-1,8-naphthalimide and 2-ethynylbenzaldehyde. In CH3CN solution, the probe 4 shows moderate colorimetric and fluorescent response to the cyanides. Upon the addition of TBACN, a new peak at 540 nm appeared in the UV-vis spectra accompanied by an instant colorimetric change from colorless to light violet. No change in the spectral pattern of chemosensor 4 was observed in the presence of other anions. Further, chemosensor 4 showed strong fluorescence with the maximum at 484 nm (λex=390 nm) in a mixture of CH3CN; however, in presence of CN - , a new emission band (λem=600 nm, light brown fluorescence) appeared along with a decrease in the emission intensity at 484 nm. Therefore, this process clearly demonstrates that chemosensor 4 can selectively detect cyanide ions by a fluorogenic on-off response, which may be attributed to the fact that the electron transfer in 1,8-naphthalimide is affected by the formation of adducts of anion with carbonyl groups. Moreover, the detailed interference experiments of chemosensor 4 in the mixed solvents were also investigated. Keywords 1,8-naphlimide; anion recognition; cyanides; nucleophilic addition; fluorescent probe