Quinoline based chromogenic and fluorescence chemosensor for pH: Effect of isomer

We report here the synthesis, characterization and pH sensing properties of a Schiff-base molecule, 2-hydroxy-5-methyl-3-((quinolin-2-ylimino)methyl)benzaldehyde (HL-2-qui) to compare the results observed for its isomers having different position of imino linkage on the quinoline unit. Fluorescence intensity of HL-2-qui at 530 nm enhanced gradually with the increase in pH of the media whereas its isomers showed ratiometric pH sensing behavior under similar conditions. HL-2-qui was colorless in acidic condition and yellow in alkaline medium under visible light while under UV light, the colors of the probe changed to indigo and fluorescent green, respectively. The chemosensor was applied in the detection of different pH regions using lemon juice and river water as the real sample. (C) 2019 Elsevier B.V. All rights reserved.