The binding behavior of receptor (L) with different anions was
studied in acetonitrile solvent. The titration was carried out in
CH 3 CN at 1 ? 10 ?5 M concentration of receptor L upon the addition
of incremental amounts from 0–500 l l of tetrabutylammonium
acetate (2 ? 10 ?4 M).
The UV–vis spectrum of the receptor (L) is characterized by two
bands centered at 321 and 373 nm (Fig. 1). As shown in Figure 1,
upon gradual increase of the acetate ion concentration, the bands
at 321 and 373 nm gradually weaken and a new band appears at
480 nm with an isosbestic point at 405 nm, indicating the forma-
tion of a new complex between the receptor (L) and the acetate an-
ion (Fig. 1) which is also responsible for the generation of pink
color after the addition of tetra butyl ammonium acetate to the
solution of the receptor. Inset of Figure 1 actually indicates the
change of absorbance with the concentration of acetate. From
the UV–vis titration data it is revealed that minimum 5.83 l M of
AcO ? can be detected by using 10 l M of receptor L. The receptor
shows linearity up to 2.61 ? 10 ?5 M concentration of acetate
(Supplementary data).