A Ruthenium(II) complex based long lifetime phosphorescent probe for copper ions and pH detection

Objective

Transition metal ruthenium(II) complex was used to prepare a dual-functional phosphorescent probe for the detection of Cu²⁺ ion and pH.

Methods

The ligand (E)-6-((thiazol-2-yl methylene)amino)-1,10-phenanthrolin-5-amine (tmpa) was prepared by condensation of 5,6-diamine-1, 10-phenanthroline with 2-formylthiazole, and then ruthenium(II) complex [Ru(bpy)₂tmpa](PF₆) (Ru-tmpa, bpy ​= ​2,2′-bipyridine) was synthesized by the coordination of tmpa with cis-Ru(bpy)₂Cl₂. Phosphorescence spectra were measured to investigate its response to metal ions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Pb²⁺, Cr²⁺, Co²⁺, Ni²⁺, Cu⁺, Cu²⁺, Fe³⁺, Fe²⁺ and Zn²⁺). The binding affinity and detecting limit of Ru-tmpa to copper ions were tested by titration experiment. The ability of the probe to monitor copper ion levels inside cells was tested by confocal microscopy imaging.

Results

Ru-tmpa can rapidly, sensitively and selectively detect Cu²⁺ in water and biological sample, and shows a sensitive phosphorescence response to pH. Ru-tmpa can penetrate cell membrane, enter the cell, and monitor the level of copper ions inside cell.

Conclusion

A novel fluorescent probe Ru-tmpa was synthesized to provide a powerful tool for the detection of Cu²⁺ and pH in biological and environmental systems.