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

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.