Spatial Electrochromism in Metallopolymeric Films of Ruthenium Polypyridyl Complexes

Thin films of poly[Ru(vbpy)2(py)2]2+ (vbpy is 4-vinyl-4‘-methyl-2,2‘-bipyridine; py is pyridine) have been deposited on electrodes by reductive electropolymerization. Photolysis of the films in the presence of chloride ion leads to photochemical loss of the pyridine ligands and sequential formation of poly[Ru(vbpy)2(py)Cl]+ and poly[Ru(vbpy)2Cl2], as determined by cyclic voltammetry and FTIR spectroscopy. Contact lithography was used to control the photosubstitution process spatially and form laterally resolved, bicomponent films with image resolution below 10 μm. Small spot X-ray photoelectron spectroscopy (XPS) was used to confirm that the photolyzed and nonphotolyzed regions of an imaged film were chemically distinct. Dramatic changes occur in the absorption spectra and redox potentials of the ruthenium complexes upon substitution of chloride for the pyridine ligands. This provides a basis for the fabrication of bicomponent, electrochromic film assemblies on optically transparent electrodes of tin doped indium oxide on glass. The spectroelectrochemical response of these films has been studied by slow scan cyclic voltammetry and potential step chronoamperometry.