Indole-based distinctive chemosensors for ‘naked-eye’ detection of CN and HSO4−, associated with hydrogen-bonded complex and their DFT study

Abstract

Colorimetric detection of anions (HSO4− and CN−) was achieved via analyte triggered colour changing of the dipodal and tripodal sensors in CH3CN–H2O (1:1). The sensors exhibited very sharp visual colour changes and fluorescence quenching–enhancing effect upon addition of the HSO4− and CN−. The large downfield shift of the NH proton signals in 1H-NMR complexation studies and quantum chemical DFT calculations proved the formation of hydrogen-bonded complexes where no proton transfer mechanism was found.