Pyrophosphate-selective fluorescent chemosensor based on ratiometric tripodal-Zn(II) complex: Application in logic gates and living cells

• Ratiometric and fluorometric ‘turn-on’ C3-symmetry tri-arm 8-hydroxyquinoline based molecular chemosensor (THL) for Zn2+.
• THL·3Zn2+ complex act as selective ‘turn-on’ fluorescent sensor for biological substrate such as pyrophosphate (PPi).
• Zn2+ elicits a drastic shift of fluorescence wavelengths from 405 to 491 nm with green fluorescent color.
• Probe can be used in a normal PBS solution for application in RAW cell imaging.

A new C3-symmetry tri-arm 8-hydroxyquinoline based fluorescent chemosensor, termed THL has been designed and synthesized, and found to be a ratiometric and selective fluorescent detector of Zn2+ over a wide range of tested metal ions. The addition of Zn2+ to the solution of THL in aqueous-organic solvent induced the formation of a 1:3 ligand−metal complex, THL·3Zn2+, which exhibits a remarkable enhanced fluorescent emission centered at 491 nm, with the disappearance of the fluorescent emission of THL centered at 405 nm due to the mechanism of internal charge transfer. These newly formed Zn2+ complex was shown to exhibit strong green fluorescence. In addition, this THL·3Zn2+ complex was found to act as selective ‘turn-on’ fluorescent sensor for pyrophosphate (PPi). Such fluorescence modulation behavior of THL and THL·3Zn2+ complex mimics the performance of a combinatorial logic circuit with INHIBIT and AND logic gates. Finally, THL was also successfully used to image intracellular Zn2+ ions in cultured RAW cells.

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