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 polyOsL1100% and hyperbranched polyOsL1x% L2y% ) 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 (ΔT) of polyOsL1100% 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 (polyOsL190% L210% ) further enhanced the electrochromic performance with ΔT = 59.4%, t c  = 0.41 s, and t b  = 0.54 s. The coloration efficiency (η) increased from 396.1 to 467.5 cm2  C-1 upon branching. A solid-state electrochromic device with polyOsL1100% is successfully fabricated to use the polymer for potential applications.