Electrochemical and Photophysical Properties of Ruthenium(II) Bipyridyl Complexes with Pendant Alkanethiol Chains in Solution and Anchored to Metal Surfaces

Luminescent ruthenium trisbipyridine complexes containing one or two mercapto-alkyl chain(s) on one of the bipyridyl units have been synthesized through a new strategy. The electrochemical and photophysical properties, determined in solution and in the solid state were compared. Deposition on electrode surfaces (gold, platinum and indium tin oxide) was realized by self-assembly and the resulting adsorbed layers were characterized by electrochemistry and fluorescence confocal microscopy. Voltammetric measurements of the films, in aqueous and in acetonitrile solution, allowed the determination of the surface coverages and the oxidation potentials of the complexes. The effect of the number of chains and the chain length in the complexes is highlighted. Emission of the adsorbed complexes was strongly quenched by the metallic surfaces, while confocal microscopy images showed aggregate formation on a μm length scale. The latter results provide considerable insight into the nature of the adsorbed layers and support deductions from the voltammetric data.