OXIDATIVE ELECTROPOLYMERIZATION OF IRON AND RUTHENIUM COMPLEXES CONTAINING ANILINE-SUBSTITUTED 2,2'-BIPYRIDINE LIGANDS

New bipyridine ligands with pendant aniline groups [4-CH2R-4'-CH2R'-2,2'-bipyridine where R = NHC6H5 and R' = H (I; anilbpy) and R = R' = NHC6H5 (II; bis-anilbpy)] and the electrochemical properties of their iron and ruthenium complexes, [Fe(anilbpy)3][PF6]2 (1), [Fe(bis-anilbpy)3][PF6]2 (2), [Ru(anilbpy)3][PF6]2 (3), [Ru(bis-anilbpy)3][PF6]2 (4), [Ru(bpy)2(anilbpy)][PF6]2 (5), and [Ru(bpy)2(bis-anilbpy)][PF6]2 (6) [bpy = 4,4'-(CH3)2-2,2'-bipyridine], are described. All complexes, except 5, form polymer films from an acetonitrile solution containing 0.1 M Bu4NClO4 on Pt and glassy carbon electrodes; 1-4 are also polymerized onto NESA glass electrodes by repetitively cycling the electrode potential between 0 and 1.1 V or 0 and 1.5 V vs SSCE. Two new redox couples arising from tail to tail and head to tail coupling of aniline groups on adjacent monomers are visible in the voltammograms during the film growth process carried out between 0 and 1.1 V. A broad, ill-defined redox couple for the tail to tail coupled aniline species is seen in polymer films grown at 1.5 V. The films exhibit voltammetric properties on all electrode materials expected for metal-centered oxidation and ligand-centered reductions when the coated electrodes are transferred to a CH3CN solution containing only supporting electrolyte. The visible spectra of the polymers on conductive glass electrodes show MLCT bands in the same region as the monomers with lambda(max) approximately 540 nm for poly-1 and poly-2 and lambda(max) = 460 nm for poly-3 and poly-4. A new absorption band appears at lambda(max) = 720 nm, assignable to a monocation of diphenylamine, for films on the conductive glass oxidized to 0.9 V, and its intensity decreases with application of increasing positive potentials, with a new band appearing lambda(max) approximate 440 nm arising from the two-electron-oxidation products of diphenylamine and benzidine.