Azo Schiff bases as colori metric and fluorescent sensors for recognition of F~-, Cd~(2+) and Hg~(2+) ions

摘要

The optical and colorimetric sensing properties of H2L~1-H2L~3 for anions were investigated by the naked eye and UV-Vis and fluorescence spectroscopy. These chemosensors show visual changes towards anions like F~- and also towards cations such as Hg~(2+) and Cd~(2+) in DMSO. Yet, other anions such as Cl~-, Br~-, NO3~-, OAc~-, HSO4~-, H2PO4~- and CN~- could not cause any color change. The ligands do not show any significant change on addition of other metal ions like Mn~(2+), Fe~(+2), Co~(+2), Ni~(2+), Cu~(+2) and Zn~(2+). The binding constant (Ka) and stoichiometry of the host-guest complex formed were determined by the Benesi-Hildebrand (B-H) plot and Job's plot method, respectively. The anion sensing abilities of the receptors toward halide anions were also monitored by electrochemical techniques.