Simple and highly electron deficient Schiff-base host for anions: First turn-on colorimetric bifluoride sensor

Here in, we have designed, synthesized and isolated sensor L, as a turn-on colorimetric chemo sensor for bifluoride ion. The acetonitrile solution contains L with tetrabutyl ammonium salts of bifluoride, cyanide and fluoride results sudden color changes from yellow to dark brown where as there is no color change observed with any other anionic guests with L. Solution state binding studies of L are carried out by UV-Vis spectrometry titration and the strengths of the chemosensor L towards bifluoride, cyanide and fluoride bindings are found to be 2.67 × 10⁵ M^-1, 4.78 × 10⁵ M^-1_, 4.45 × 10⁵ M^-1 respectively. The strength and sensitivity of the absorbance based assay with L for bifluoride ion, are found to be 2.67 × 10⁵ M^-1 and 0.7 μM respectively, which is the best (highest binding constant and lowest LOD) ever reported in the literature. In order to use this sensor in practical application, we also prepared a cassette which is fabricated with sensor L and we succeeded to sense bifluoride ion.