2, 2′-Dihydroxyazobenzene-based fluorescent system for the colorimetric ‘turn-on’ sensing of cyanide

2, 2′-Dihydroxyazobenzene (DHAB) demonstrated high sensitivity and low selectivity toward three anions: CN−, CO32−, and HCO3−. In the presence of Cu(II), complex DHAB–Cu(II) could give rise to enhanced fluorescence intensity by about 45-fold at 590 nm and visible red-to-reddish orange color change upon the addition of cyanide by utilizing an indirect method, while no changes were observed in the presence of other anions, including F−, Cl−, Br−, I−, H2PO4−, CH3COO−, NO3−, CO32− and HCO3−, and SO42−, making the DHAB–Cu(II) complex a selective and sensitive cyanide chemosensor.