Visible light‐triggered pyrazole‐functionalized reversible ionophore for selective monitoring of aluminium (III) ion

Abstract

A photo‐switchable ionophore, (E)‐4‐([2‐hydroxy‐3‐methoxybenzylidene]amino)‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one (S1), was rationally designed and developed for the visible light‐triggered selective and efficient transport of Al (III) ions. The non‐fluorescent probe distinctly manifests its green light at 518 nm in presence of Al (III) ion upon irradiation at 405 nm and showed a turned‐off emission with EDTA in ethanol. The binding mode and structural perspective of S1 were assessed through X‐ray crystallography, spectrophotometry, spectrofluorimetry, 1H nuclear magnetic resonance (NMR) titration, electrospray ionization mass spectrometry (ESI‐MS) analysis and computational calculations, suggesting a 1:1 binding stoichiometry and a distorted tetrahedral coordination geometry of S1‐Al complex. The testing strip was also developed with S1 coating for colourimetric and naked‐eye detection of Al (III) ion as evident from the green fluorescence upon irradiation at 365 nm. Further, a bioimaging study of S1 in human colon living cells (HP‐29) revealed the presence of Al (III) ion through a bright green fluorescence in HP‐29, indicating the potentiality of S1 to trace Al (III) in living cells. Additionally, cytotoxicity studies by MTT assay and staining analysis ensured that the probe might be an efficient and sensitive chemosensor for monitoring Al (III) ion in drug delivery and biological applications.