Imine containing benzophenone scaffold as an efficient chemical device to detect selectively Al3+

Abstract

A benzophenone-based Schiff base 1 has been utilized as a fluorescence chemosensor for the selective detection of Al³⁺. The probe was synthesized in one step, and found to be non-fluorescent due to a combination of photoinduced electron transfer (PET), excited state intramolecular proton transfer (ESIPT) and E/Z isomerism. Upon addition of Al³⁺ to a methanolic solution of 1, the development of a strong fluorescence signal was observed with an attractive glowing green emission. This was due to the inhibition of PET, ESIPT and E/Z isomerism, and the activation of chelation enhanced fluorescence (CHEF). The quantum yield of 1–Al³⁺ was found to be 0.17. The selectivity was tested with 24 different metal and non-metal ions, and established using various spectroscopic tools. The strong affinity of compound 1 for Al³⁺ was also proven by ¹H NMR and mass spectroscopy.