Figure 3 actually shows the selectivity for acetate over the other
anions which is shown by the green bar. The slight interference of
benzoate and fluoride is shown by the violet and olive bars but it
cannot be detected by the naked eye which is shown in the inset.
From the experimental data, it can be concluded that the receptor
L possesses high selectivity and sensitivity toward acetate in aceto-
nitrile medium. The other anions except benzoate had no practical
significant influence. The color changes are most probably due to
the formation of hydrogen bonds or deprotonation of –OH group
of receptor L on the addition of the acetate ion which is shown
in Scheme 2