Solvent-tuned discriminant sensing of Al3+, Mg2+ and HF2− by vanilinyl-picolinyl hydrazide Schiff base

Abstract

Herein, the vanilinyl-picolinyl hydrazide dyad Schiff base (HVPh) was structurally characterized by single-crystal X-ray diffraction crystallography. The molecule exhibits an intense green fluorescence in the solid state and serves as a solvent-tuned dual detector to Mg²⁺ and Al³⁺ and a secondary sensor to HF₂⁻. Mg²⁺ imparts a yellow emission at 522 nm (LOD, 45 nM) in DMSO, whereas an intense blue emission is observed for Al³⁺ in pure water at 460 nm (LOD, 7.4 nM). The probe formed a 1 : 1 complex with Al³⁺ and a 1 : 2 complex with Mg²⁺, and the composition of these complexes was established by NMR, mass and FTIR spectral data. Studies on the anion sensitivity of these complexes showed that HF₂⁻ efficiently quenched the emission of the complexes, and the LODs were far below the WHO recommended data (Mg²⁺, 200 mM; Al³⁺, 7.41 mM; and F⁻, 3.68 μM). A recovery study was performed to check the practical applicability of the probe using drinking water supplied by Kolkata Municipality Corporation in the Jadavpur University campus. The molecular INHIBIT logic gate was also constructed by the sensor. The DFT and TDDFT computation techniques were used to explain the experimental findings.