Synthesis, photophysical, and electrochemical properties of a new family of trinuclear Ru(II) polypyridine complexes

Abstract

A series of four tripodal ligands L^1–4 were prepared by the reaction of 9-(2-hydroxy)phenylimino-4,5-diazafluorene with 1,3,5-tris(bromomethyl)benzene, 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, tris(2-chloroethyl)amine hydrochloride, and pentaerythrityl tetratosylate, respectively, in DMF solution under nitrogen. For each ligand, Ru(II) complexes were prepared by refluxing Ru(bipy)₂Cl₂ · 2H₂O and ligand in 2-methoxyethanol. Photophysical behaviors of these Ru(II) complexes have been investigated by UV-Vis absorption and luminescence spectrometry. They display metal-to-ligand charge transfer absorption at 442 nm in MeCN solution at room temperature and emission at 574 nm in EtOH–MeOH (4 : 1, v/v) glassy matrix at 77 K. Electrochemical studies of the Ru(II) complexes show one Ru(II)-centered oxidation at 1.33 V and three ligand-centered reductions.

Keywords:

• Tripodal ligand
• Ru(II) complex
• UV-Vis absorption
• Luminescence
• Electrochemistry

Acknowledgments

We are grateful to the Yunnan Provincial Science and Technology Department (2010ZC148, 2006B0081M, 2009ZD008) for the financial support.