New Schiff Base-Linked Arylazopyrazoles as Reagents for the Photometric Detection of Fluoride Ions

A novel class of reagents (L1-3) containing arylazopyrazole moiety linked to a Schiff base have been synthesized and investigated for anion sensing applications. All three compounds exhibited excellent sensitivity and selectivity toward selective colorimetric detection of F- in dimethyl sulfoxide. F- sensing mechanisms have been explored by various spectroscopic techniques, viz., H-1 NMR, IR, UV-visible, and fluorescence spectroscopy. A clear qualitative and quantitative detection of F- was possible with specificity and good sensitivity with L2 giving optimum results. The LOD value of L2 toward F- was found to be 7 & mu;M. These reagents were applied for fluoride detection in commercial toothpaste as well.