pH-induced molecular switch of a novel trinuclear Ru(II) polypyridyl complex

Ligand 1,3,5-tris(1,10-phenanthroline-[5,6-d]imidazol-2-yl)benzene (L) and corresponding novel trimetallic Ru(II) polypyridyl complex [(bpy)6L(RuII)3](PF6)6 have been synthesized. UV–vis absorption and fluorescence spectra of the complex change obviously over the pH range 1.82–12.29. This complex acts as pH-induced off–on–off fluorescence switch through protonation and deprotonation in buffer solution.