Design and synthesis of Schiff base ligands and their applications in metal ion sensing

Abstract

We have designed and synthesized the Schiff base ligands HL1 {E-1-(((pyren1-ylmethyl) amino) methyl) naphthalen-2-ol)}, HL2 ((Z)-5-((3,4- dihydroxybenzylidene) amino) isophthalic acid) and ((Z)-5-((2-hydroxy-3- methoxybenzylidene) amino) isophthalic acid) by simple condensation reaction in between primary amine and aldehyde. These Schiff base linkers have been characterized by the Mass spectrometry, 1 H NMR spectrometry. HL1 and HL2 have been further analysed by Ultraviolet-Visible and fluorescence spectrometry. These ligands are highly selective towards the sensing of Al3+ among a wide range of metal cations. Sensing capability of these ligands are observed by the UV-Vis. and fluorescence titration methods. Titration of ligands with Al3+ ions by the fluorescence spectroscopy showed a distinct fluorescence quenching (turn off) mechanism at specific wavelength. Schiff base ligands (HL1 and HL2) was found to be highly selective and sensitive towards the sensing of Al3+ even in the presence of other metal cations with LOD value 14 nm for HL2. Limit of detection for HL1 is 24 nM and for HL2 is 14 nm