A simple Schiff base molecular logic gate for detection of Zn2+ in water and its bio-imaging application in plant system

Selective and sensitive detection of Zn2+ is important both in chemistry and biology. A water soluble simple Schiff base ligand, 2-[(2-hydroxyethylimino)methyl]lphenol (H(2)SalEt) was synthesized by one step condensation reaction between salicylaldehyde and 2-amino-1-ethanol in ethanol medium which is demonstrated to have utility in selectively determining Zn2+ ions over other common metal ions in (100 mM HEPES buffer, pH 7.4) solution displaying a significant colour change yellow to blue under UV light. The binding of HSalEt-Zn2+ was tracked by elemental analysis, mass spectra analysis, FT-IR, H-1 and C-13 NMR spectroscopy in CH3OH-d(4). Single crystal X-ray diffraction studies reaffirm the binding modes of HSalEt-Zn2+ aggregate. The ligand (H(2)SalEt) exhibits a weak fluorescence intensity (quantum yield, Phi = 0.054) and the presence of zinc ions 14 fold enhancement of fluorescence intensity (quantum yield, Phi = 0.769). H(2)SalEt allows the detection of Zn2+ at 10(-7) (M) level. Addition of chelating agent EDTA to a solution containing HSalEt-Zn2+ complex leads to immediate quenching of fluorescent intensity, making the chemosensor H(2)SalEt a reversible one. In aqueous solution, H(2)SalEt induces a (2:1) complex formation with Zn2+ ions indicated by Job's plot analysis. 'OR' and 'Keypad lock' logic gates were created that respond to Zn2+ and Al3+ inputs with absorbance (359 nm) and fluorescence output (454 nm) signals. In order to further explore the sensing potential of H(2)SalEt, two different kinds of cells, Azotobacter chroococcum and Candida albicans were used for in vitro investigation of the intracellular Zn2+ by H(2)SalEt. Fluorescence imaging of translocation of Zn2+ through the transparent stem of rice seedling, Oryza sativa, proved in vivo bio imaging capability of H(2)SalEt. (C) 2016 Elsevier B.V. All rights reserved.