Synthesis and X-ray Structures of Potential Light-Harvesting Ruthenium(II) Complexes

Abstract

We synthesized the luminescent ruthenium(II) polypyridyl complexes of type [Ru(bpy)2(L1)][ClO4]2 (1) (where L1 = 4,4-dicarboxy-2,2-bipyridine); [Ru(bpy)2(L2)][ClO4]2 (2); and [Ru(L2)3][ClO4]2 (3) (where L2 = 4,4-dimethanol-2,2-bipyridine). Photo-physical and electrochemical properties of the Ru(II) complexes were investigated along with the emission vs. pH. This reveals that the carboxylic acids in the 2,2-bipyridine ligand had a more important influence on the photophysical and electrochemical properties of the Ru(II) complexes than alcohol. The crystal structure of the Ru(II) complexes 1–3 is also discussed in this paper. The cyclic voltammetry of 1–3 yields a reversible RuIII/II wave that shifts 1.4–1.2 V. UV/Visible absorbance spectroscopy reveals that Metal-to-Ligand Charge Transfer (MLCT) transitions shift to lower energy upon deprotonation of the complex.