Dinuclear asymmetric ruthenium complexes with 5-cyano-1,10-phenanthroline as a bridging ligand.

New dinuclear asymmetric ruthenium complexes of the type (bpy)(2)Ru(5-CNphen)Ru(NH(3))(5) (bpy = 2,2'-bipyridine; 5-CNphen = 5-cyano-1,10-phenanthroline) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. The structure of the cation (bpy)(2)Ru(5-CNphen)Ru(NH(3))(5) has been determined by X-ray diffraction. The mononuclear precursor Ru(bpy)(2)(5-CNphen) has also been prepared and studied; while its properties as a photosensitizer are similar to those of Ru(bpy)(3), its luminescence at room temperature is quenched by a factor of 5 in the mixed-valent species (bpy)(2)Ru(II)(5-CNphen)Ru(III)(NH(3))(5), pointing to the occurrence of intramolecular electron-transfer processes that follow light excitation. From spectral data for the metal-to-metal charge-transfer transition Ru(II) --> Ru(III) in this latter complex, a slight electronic interaction (H(AB) = 190 cm(-1)) is disclosed between both metallic centers through the bridging 5-CNphen.