Polymeric complexes of transition metal ions as electrochromic materials: Synthesis and properties

Materials exhibiting reversible color changes under an electric stimulus, called electrochromic materials, have been drawing great research interest due to their applications as active materials in organic electronics. New electrochromic materials exhibiting multi-electrochromic properties in a wide range of colors with high contrast ratios and short response times are still in great demand. Well defined redox properties and intense charge transfer absorptions of transition metal complexes make them promising materials for use as electrochromic materials. The absorption wavelength and observed color of transition metal complexes significantly depend on the redox state of both the metal ion and the ligand, and their properties can be modified by changing the ligands or metal ions. This review summarizes the electrochromic properties of metallopolymers, coordination sheets as well as nanocomposites containing transition metal complexes, which can be used as active materials in electrochromic devices. (C) 2019 Elsevier B.V. All rights reserved.