Electrochromic and Conductivity Behavior of Tris[Ester-Substituted Bipyridine]Ruthenium[II] Polymers on Electrodes

Complexes of ruthenium with 2,2′-bipyridines having electron-withdrawing ester functions in the 5,5′ positions have been prepared, and they are polymerizable. Films can be cast on electrodes from solutions of the monomer and then polymerized thermally. Once formed, the films are electroactive and quite stable in the absence of O₂. The ruthenium complexes in this polymer have a rich electrochemistry and can exist in seven stable oxidation states. The spectral properties of the polymer are such that, as the oxidation state of the complex is changed successively from 2+ to 4-, the polymer undergoes vivid changes in color. The material is thus of interest as an electrochromic material. Additionally, when the polymer is reduced to the formal zero-valent form it becomes an ohmic conductor with semiconductorlike properties.