Vanillinyl thioether Schiff base as a turn-on fluorescence sensor to Zn2+ ion with living cell imaging

-Vanillinyl thioether Schiff base, 6.6'-(( 1Z.1Z')-(((ethane-1,2-diylbis(sulfanediyl)) bis(2,1phenylene)) bis(azanylyldene))bis(methanylylidene))bis(2-methoxyphenol) (H2L), selectively senses Zn2+ in presence of large number of cations and anions (except H2PO4-) and serves as a "turn-on" fluorescence receptor enhancing emission at 555 nm by 275 fold. The limit of detection (LOD) for Zn2+ is 62 nM and is far below the guidelines of the World Health Organization (46 mu M) as the maximum allowable concentration in drinking water. Formation of the 1:1 metal-to-ligand complex has been ascertained by H-1 NMR, mass-spectral analysis and Job's plot. Addition of similar to 2.0 equivalent of H2PO4- (10 mM) resulted in quenching of emission of the complex. The DFT and TD DFT computation have been carried out with ligand and complex to interpret spectral properties. The selective sensitivity of probe, H2L, has successfully been applied to the detection of intracellular Zn2+ in Vero Cells (African Green Monkey Kidney). (C) 2016 Elsevier B.V. All rights reserved.