Electrochromic Os(II)-Based Metallo-Supramolecular Polymers

This work presents the preparation of a series of novel Os(II)-based metallo-supramolecular polymers (polyOss: linear polyOsL1(100%) and hyperbranched polyOsL1(x%)L2(y%)) that show a broad absorption spanning 312 to 677 nm and a low Os(II)/(III) redox potential of 0.94 V. The electrochromic properties of a polyOs film cast on an ITO substrate is investigated. The change in transmittance (Delta T) of polyOsL1(100%) is 49.9%, and the switching times for coloration (t(c)) and bleaching (t(b)) are 0.70 and 0.82 s, respectively. The introduction of a 10% branching structure (polyOsL1(90%)L2(10%)) further enhanced the electrochromic performance with Delta T = 59.4%, t(c) = 0.41 s, and t(b) = 0.54 s. The coloration efficiency (eta) increased from 396.1 to 467.5 cm(2) C-1 upon branching. A solid-state electrochromic device with polyOsL1(100%) is successfully fabricated to use the polymer for potential applications.