A highly selective and sensitive fluorescent turn-on Al³⁺ chemosensor in aqueous media and living cells: Experimental and theoretical studies

A highly selective and sensitive fluorescent chemosensor (1) based on a 2-aminobenzoic acid Schiff base has been synthesized in one step. The binding properties of 1 with metal ions were investigated by fluorescence, UV-vis, ¹H NMR and electrospray ionization mass spectra. This sensor exhibited enhanced fluorescence in the presence of Al³⁺ in aqueous solution and also in living cells. The sensing mechanism of 1 toward Al³⁺ was explained by DFT/TDDFT calculations. The binding constant was determined to be 3.1 × 10⁸ M^-1 which is one of the highest binding affinities among such simple Schiff bases for Al³⁺ in buffer solution. The calibration curve for the analytical performance of Al³⁺ was found to be linear over a concentration range with a very low detection limit of 290 nM (3σ).