A robust fluorescent chemosensor for aluminium ion detection based on a Schiff base ligand with an azo arm and application in a molecular logic gate

Abstract

In this present work we have reported the synthesis and structural characterisations of a N₂O₂ donor Schiff base chemosensor with an azo arm (H₂L). Various spectroscopic tools like single crystal X-ray, NMR, UV-vis, FTIR, ESI-mass spectrometry etc. have been deployed to develop the present work. In recent years a number of azo derived chemosensors have been reported by different research groups. This is first time we are reporting the design and properties of an azo derived chemosensor (H₂L) for the detection of aluminium ions in semi aqueous medium. It has been found that it selectively senses Al³⁺ ions in semi aqueous solution. Here, the sensing process is mainly based on a chelation enhanced fluorescence process (CHEF). It has very high selectivity over other metal ions and anions. A detailed literature survey has been carried out and compared with this work. It has an appreciably low detection limit i.e. 6.93 nM. ¹H NMR titration was carried out to support the plausible complexation process. 1 : 1 stoichiometry binding between the chemosensor and Al³⁺ ions has been confirmed from Job's plot. An inhibition molecular logic gate has been constructed using chemosensor (H₂L), where Al³⁺ and EDTA act as inputs and fluorescence emission is the output. The structural and electronic parameters of the chemosensor (H₂L) and complex [AL(L)]NO₃ have been studied in detail using theoretical tools like DFT and TDDFT.