Highly selective and sensitive chemosensor for Al(III) based on isoquinoline Schiff base.

As a colorimetric and fluorescent turn-on sensor to Al3+, N'-(2-hydroxybenzylidene)isoquinoline-3-carbohydrazide (HL) has been easily synthesized. The fluorescence intensity increases by 273 times in the presence of Al3+ at 458 nm. Meanwhile, the experiment data indicate that the limit of detection for Al3+ is 1.11 × 10-9 M. Remarkably, the blue fluorescence signal of HL-Al3+ could be specially observed by the naked eye under UV light and is significantly different from those of other metal ions. Fluorescence switch based on the control of Al3+ and EDTA proved HL could act as a reversible chemosensor. According to ESI-MS result and the Job's plots, the 2:1 coordination complex formed by HL and Al3+ could be produced. Density functional theory calculations were performed to illustrate the structures of HL and complex. The cell imaging experiment indicates that HL can be applied for monitoring intracellular Al3+ levels in cells.