Near-infrared electrochromism in mixed-valent diruthenium complexes

Abstract

The potential applications and evaluation parameters of electrochromic devices are first introduced, together with the basic requirements and current research status of near-infrared electrochromic materials. On the basis of the recent research progress in this laboratory, the design, synthesis, electrochemical and spectroscopic properties, and the metal-metal electronic coupling of cyclometalated diruthenium complexes are then presented. The presence of M-C bonds significantly decreases the redox potential of the metal center and enhances the intermetallic electronic coupling. In the mixed-valent state, these diruthenium complexes display intense intervalence charge-transfer transitions in the near-infrared region and the energy and intensity of these transitions can be modulated by changing the bridging and/or terminal ligands. By using reductive or oxidative electropolymerization, these dimetallic complexes can be deposited onto electrode surfaces as metallopolymeric films. The resulting films exhibit multistage near-infrared electrochromism with low operation potential, short response time, good contrast ratio, and long optical memory time.