A new dihydrazone based “turn on” fluorescent sensor for Zn(II) ion in aqueous medium

• A new colorimetric and fluorescent “turn-on” chemosensor I for zinc was developed;
• I shows chelation enhanced fluorescence effect (CHEF) in presence of zinc
• CHEF of I is selective for zinc ions even in presence of other interfering elements
• Sensitivity towards zinc ion is more effective in pH 8.6
• Facile proton dissociation in the excited state renders better ion-sensing ability.

A new simple dihydrazone based colorimetric and fluorescent “turn-on” chemosensor (disalicyladehyde succinoyldihydrazone, I) for Zn(II) was designed and synthesized. The photophysical behavior of the ligand and metal coordinated complex was characterized by steady state and time-resolved fluorescence, density functional theory calculation in combination with 1H NMR and mass spectroscopy results. The compound acts as a highly selective and sensitive detector of Zn(II) in aqueous medium with almost six times increase in fluorescence intensity. The optimum condition for sensing ability of I with a detection limit of ca. 2 μM of Zn(II) was found at solution pH 8.6 and at excitation wavelength of 380 nm. The other interfering elements, including Cd(II), show either no or very little change in fluorescence intensity under similar experimental conditions.

The fluorescent “turn-on” chemosensor (disalicyladehyde succinoyldihydrazone, I) is found to be a selective detector of zinc (II) with about 2 μM sensitivity.Figure optionsDownload as PowerPoint slide