Three colour electrochromic metallopolymer based on a ruthenium phenolate complex bound to poly(4-vinyl)pyridine

The photonic and electrochemical properties of a novel Ru–phenolate based metallopolymer are reported. The complex undergoes a ruthenium based reversible oxidation at approximately +0.400 V and irreversible box ligand oxidation at +0.800 V vs. Ag/AgCl. Oxidation of thin films in aqueous electrolyte at +0.500 V reversibly switches the colour from wine red to light green and a red orange colour is observed for mixed redox composition. In contrast, oxidation at potentials more positive than +1.500 V shows no visible colour change but produces a change in the near infra-red region. To determine the electrochromic switching rate and to identify the rate determining step of the, scan rate dependent cyclic voltammetry was performed under semi-infinite linear diffusion conditions in aqueous lithium perchlorate. These data reveal that the homogeneous charge transport diffusion coefficient, D_CT, is 3.6 ± 0.2 × 10⁻¹³ cm² s⁻¹, i.e., under these conditions it takes approximately 90 s to fully oxidise a 100 nm thick film.