Solvent-dependent selective fluorescence sensing of Al3+ and Zn2+ using a single Schiff base

The selective assay of Al3+ and Zn3+ ions is reported using fluorescence enhancement of a simple Schiff base receptor 1 (1 = 1-((E)-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino)methyl)naphthalen-2-ol) in aqueous solvents. The Schiff base receptor 1 showed a turn-on fluorescence in the presence of Al3+ in a mixture of methanol-water, as a result of a restricted C=N isomerization mechanism. The ion selectivity of 1 could be switched for Zn2+ by swapping the solvent from methanol-water to DMF-water mixture. In particular, this chemosensor could clearly distinguish Zn2+ from Cd2+. The binding properties of 1 with the metal ions were investigated by UV-vis, fluorescence, electrospray ionization mass spectroscopy and H-1 NMR titration. (C) 2014 Elsevier B.V. All rights reserved.