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

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 H-1-NMR complexation studies and quantum chemical DFT calculations proved the formation of hydrogen-bonded complexes where no proton transfer mechanism was found.