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 PtII complex [Pt3 (μ3 -pydt)2 (bpy)3 ]2+ (H2 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 [Pt3 X2 (μ3 -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.