Abstract
Tetrapodal ligands tetrakis{4-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}methane (L 1 ), tetrakis{3-((1,10-phenanthroline-[5,6-d]imidazol-2-yl)phenoxy)methyl}methane (L 2 ), and corresponding Ru(II) complexes [(bpy) 8 L 1–2 (Ru II ) 4 ](PF 6 ) 8 , shortly called Ru–L 1–2 , have been synthesized and characterized. The pH effects on UV–vis absorption and fluorescence spectra of the two complexes are studied, and ground- and excited-state ionization constants of the two complexes are derived. The two complexes act as pH-induced “off–on–off” fluorescence switches through protonation and deprotonation in buffer solution at room temperature. Two novel tetranuclear Ru(II) complexes with imidazole rings uncoordinated to the metal ion center have been prepared. The two complexes behave as pH-induced off–on–off fluorescence switches due to their interesting ptoton-dependent photophysical properties. ► Synthesis two tetranuclear Ru(II) complexes with imidazole rings. ► The two complexes show interesting proton-dependent photophysical properties. ► The two complexes act as “off–on–off” fluorescence pH switches.
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