Mutual effects on the spectroscopic and electrochemical properties of μ3-oxo-trinuclear ruthenium complexes modified with a bridged [Ru(2,2′-bipy)2(CN)] moiety

The asymmetric dimers [Ru3O(CH3COO)(6)(py)(2)(B)Ru(2,2'-bipy)(2)(L)](PF6)(2), where B = 4,4'-bipy or bpa (1,2-bis(4-pyridyl) ethane) and L = Cl- or CN-, have been characterised based on spectroscopic and electrochemical techniques and both the influence of the CN- coordination and of the bridging ligand have been studied. In the dimer where the bridging ligand is the pi-conjugated 4,4'-bipy, the coordination of the cyanide ligand to the [Ru(2,2'-bipy)(2)] moiety shifts to more positive values all the E-1/2 associated with the [Ru3O] core. The influence of the [Ru3O(CH3COO)(6)(py)(2)] fragment on the spectroscopic properties of [Ru( 2,2'-bipy)(2)] has been probed by photophysical assays; at room temperature, no luminescence is detectable for the dimer where B = 4,4'- bipy, whereas the complex where B = bpa shows luminescence with low values of phi compared to the precursors [Ru( 2,2'-bipy)(2)(B)(CN)]PF6. At 77 K both dimers show weak luminescence. Based on DeltaG(degrees) values it is proposed that the main quenching pathway operates through an electron transfer mechanism.