Robust Triplatinum Redox-Chromophore for a Post-Synthetic Color-Tunable Electrochromic System

An electrochromic system showing ease of color tunability has been constructed using a triple-decker Pt-II complex [Pt-3(mu(3)-pydt)(2)(bpy)(3)](2+) (H(2)pydt=2,6-pyridinedithiol, bpy=2,2 '-bipyridine). The divalent complex undergoes electrochemically quasi-reversible two-electron transfer coupled with the coordination/dissociation of axial ligands, forming higher valent Pt(+2.67) species [Pt3X2(mu(3)-pydt)(2)(bpy)(3)](2+) (X=Cl-, Br-, and SCN-). These higher valent species exhibit characteristic colors ranging from red to cyan depending on the counter anion X- of the electrolyte. The triple-decker structure provides a novel multicolor electrochromic system with favorable stability and reversibility. Theoretical calculations indicate that the colors of the Pt(+2.67) species are tunable by the trans influence of the axial ligand X-. This novel strategy of post-synthetic color-tuning using triplatinum systems should enable the facile preparation of colorful electrochromic devices without any complicated procedures, which may find application in flexible displays, optical devices, and sensors.