RESONANCE RAMAN SPECTROELECTROCHEMICAL AND STRUCTURAL STUDY OF REDUCED RUTHENIUM(II) COMPLEXES WITH BINAPHTHYRIDINE-BASED LIGANDS

The spectroscopy of electrochemically reduced ruthenium(II) complexes with 2,2'-biquinoline and 2,2'-binaphthyridine ligands have been inves tigated. These compounds are: [Ru(bn)(bpy)(2)][BF4](2) (where bn = 2,2 '-bi-1,8-naphthyridine and bpy = 2,2'-bipyridyl); [Ru(dbn)(bpy)(2)][BF 4](2) (where dbn = 3,3'-dimethylene-2,2'-bi-1,8-naphthyridine); [Ru(db n)(3)][BF4](2); [Ru(dbq)(bpy)(2)][BF4](2) (where dbq = 3,3'-dimethylen e-2,2'-biquinoline). Resonance Raman spectra of the parent species sho wed the bichromophoric nature of the visible absorptions of the hetero leptic complexes; both bpy and non-bpy ligand vibrations are enhanced depending on the excitation wavelength. Changes in the electronic abso rption spectra for the complexes upon electrochemical reduction sugges t the reducing electron is localised on the non-bpy ligand. For the co mplexes with the dimethylenebinaphthyridine ligand the second reductio n also appears localised on the non-bpy ligand. Resonance Raman spectr a of the reduced species confirm that the first and second reduction a re based on the dbn ligand. Single crystal structures of [Ru(bn)(bpy)( 2)][BF4](2) and [Ru(dbn)(bpy)(2)][BF4](2) have been determined and sig nificant distortions of the ligands are apparent.