Isophorone‐boronate ester: A simple chemosensor for optical detection of fluoride anion

A highly selective isophorone‐boronate ester based chemosensor, (1), having a dicyanovinyl moiety as a convenient colorimetric probe, has been designed. Different types of anionic analyte such as CH3COO−, ClO4−, Cl−, F−, PF6−, Br− and HSO4− were tested and among them only highly nucleophilic F− anion displayed significant response towards the sensor. Addition of the fluoride anion across the boron atom disrupts the π‐conjugation thereby shifts the absorption wavelength towards the redshift region due to the decrease in the HOMO‐LUMO energy gap and a colour change from yellow to blue is observed under visible light condition. The detection limit of this probe was calculated to be 3.25 × 10—8 M for fluoride anion. The binding constants and the detection limits of the sensor were calculated using absorption titration studies. The silica gel TLC strips dip‐coated by the chemosensor (1) revealed a colour change from yellow to brick red to naked eye. ESP surfaces of molecules (1) and (1.F‐) with Mulliken atomic charges at dicyano quaternary carbon and boron in the conjugate (1).