Luminescent pH sensor of a novel imidazole-containing hexanuclear Ru(II) polypyridyl complex

• We synthesized one Ru(II) complex with imidazole uncoordinated to Ru(II) center.
• The complex shows pH-dependent photophysical properties.
• The complex acts as an “off–on–off” luminescent pH sensor.

Hexapodal ligand H6L containing imidazole rings has been prepared by the reaction of 1,10-phenanthroline-5,6-dione with 1,2,3,4,5,6-hexakis[(3-formylphenoxy)methyl]benzene. The Ru(II) polypyridyl complex [{Ru(bpy)2}6(μ6-H6L)](PF6)12 (bpy = 2,2′-bipyridine) has been synthesized by the reaction of Ru(bpy)2Cl2·2H2O with ligand H6L. The pH effects on the UV–vis absorption and emission spectra of the complex have been studied. The ground- and excited-state ionization constants of the acid–base equilibria have been calculated according to the absorbance and emission data. The complex acts as an off–on–off luminescent pH sensor through two successive deprotonation processes of imidazole rings, with a maximum on–off ratio of 5 in buffer solution.

One novel hexanuclear Ru(II) complex with imidazole units uncoordinated to the Ru(II) center has been synthesized. The complex acts as an “off–on–off” luminescent pH sensor through two successive deprotonation processes of imidazole units.Figure optionsDownload as PowerPoint slide