[Paper] Designed Electrochromic Display Devices with Ru(II)-Based Metallo-Supramolecular Polymer For Experience-Based Exhibits at Ehime Prefectural Science Museum

Abstract

Electrochromism is electrochemical color changes in material and Tungsten oxide and viologens are the representative ones 1). The electrochromic (EC) materials are used as smart window or anti-glare mirror in airplanes, vehicles, and office. Recently, metallosupramolecular polymer (MSP) has been investigated as a novel EC material 2-11). MSPs have advantages such as the solution-based processability and the wide color variation, compared with the conventional EC materials. MSPs are synthesized by complexation of metal ion and multi-topic organic ligand. The 1:1 complexation of metal ion having six coordination sites (Fe, Co, Ru etc.) and ditopic ligand bearing two tridentate coordination moieties (e.g., bisterpyridines) results in the formation of linear MSPs (Fig. 1a). The polymer structure is controlled by changing the ligand. For example, twodimensional nanosheets with a honey-comb structure is obtained by the complexation of metal ion having six coordination sites and ditopic ligand bearing two BIDENTATE coordination moieties (e.g., bisbipyridines), because a metal can be complexed with three bidentate moieties (Fig. 1b) 12). Abstract Metallo-supramolecular polymers (MSPs) are a novel type of electrochromic (EC) materials. Ru(II)based MSP (polyRu) composed of Ru(II) and bis(terpyridyl)benzene showed reversible color changes between orange and pale green. The orange color was caused by the metal-to-ligand charge transfer (MLCT) absorption in polyRu and disappeared by the electrochemical oxidation of Ru(II) to Ru(III). The pale green was returned to the original orange by the electrochemical reduction of Ru(III) to Ru(II). EC devices with polyRu were fabricated by the combination of an electrolyte solution, counter material, and two ITO glasses. The character images were displayed on the EC devices using insulating films. The insulating films prevented the electron transfer between the ITO glass and the polyRu layer and made the image stand out in the device. The fabricated EC display devices were presented at a science museum of Japan as experience-based exhibits.