Effect of ‐OMe Substituent on Salicylaldehyde Schiff Base to Influence the Zn²⁺ Sensitivity and the Cancer Cell Line Imaging

Abstract

Functional group of a molecule monitors the chemical selectivity and the structure regulates the rate of the reaction. Thus, structure‐function relation controls the overall sensitivity of the chemosensor. In this work, three congeneric Schiff bases with common amine, 2,2/‐(propane‐1,2‐diylbis(oxy))dianiline with methoxy substituted Salicylaldehyde are synthesised and have been used to examine the selectivity and sensitivity to the metal ions in 9:1 (v/v) acetonitrile/water (10 mM HEPES buffer, pH 7.4) medium. The probes display prominent fluorescence turn‐on emission when bonded with Zn2+ over sixteen other metal ions with very low limit of detection (LOD), 2.2 to 12.3 nM. Structure with bulkiness has low sensitivity to Zn2+ which may be due to steric crowding about the binding centres of the chelating motif. The selectivity for Zn2+ ion may ascribe to chelation enhancement of fluorescence (CHEF) effect. The probes are characterized by 1H and 13C NMR, IR, HR‐MS and elemental analysis. The metal: ligand ratio of the Zn(II)‐complexes follows 1:1 molar ratio and has been established by Job's plot, Benesi–Hildebrand plot and HR‐MS data. All the probes have been successfully applied to the detection of intracellular Zn2+ ion in Human liver cancer cell line, HepG2.

A Vanillinyl‐Hydrazone Schiff Base: Recognition of Mg2+, Zn2+, Cd2+ and I− by Turn‐On Fluorescence Method

“…C. A. DeRosa et. al reported methoxy substitution in difluoroboron benzoylacetonate complexes exhibiting color‐tunable phosphorescence and our research group also previously repoted the effect of ‐OMe substituent on salicylaldehyde based Schiff base to influence the Zn 2+ ion sensitivity. Again our research group already reported a Schiff base molecule which exhibited fluorescence sensitivity enhancement towards Zn 2+ , Cd 2+ and I − .…”