Anion Effects to Electrochromic Properties of Ru-based Metallo-supramolecular Polymers

Abstract

Ru(II)-based metallo-supramolecular polymers with different counter anions (Cl^-, (CF₃SO₂)₂N^-, CF₃SO₃^-, BF₄^-, ClO₄^-, PF₆^- and CO₃^2-) were prepared by anion exchange reaction in the film state. In the UV-vis. spectra, the MLCT absorption was observed around 510 nm and the maximum wavelength was slightly different among the polymers. The polymers with “soft” counter anions such as (CF₃SO₂)₂N^-, CF₃SO₃^-, ClO₄^- and PF₆^- showed a reversible redox wave based on the redox of Ru(II)/(III). It was revealed that the redox is diffusion-controlled. The polymers with (CF₃SO₂)₂N^-, CF₃SO₃^-, ClO₄^-, PF₆^- and BF₄^- showed reversible EC behavior. The polymers with (CF₃SO₂)₂N^- and ClO₄^- exhibited the highest durability and the quickest response (3.69/0.98 s), respectively, among the polymers. The polymer with (C₃SO₂)₂N^- has the highest color efficiency (270.3 cm² C^-1). These results suggested that the hardness/softness of counter anions greatly influences the EC properties of the Ru(II)-based metallo-supramolecular polymers.