Synthesis and Electrochromic Properties of New Terpyridine-Triphenylamine Hybrid Polymers

Six metallic terpyridine-based complexes MLn (M = Ru, Fe; n = 1-3) with two triphenylamine sides have been designed and synthesized with the purpose of both providing four terminal active sites for the following electrochemical polymerization and prolonging the electrochromic memory time and the durability. Within the voltage range from 0 to 2 V, the obtained electro-polymerized films of polymers (p-MLn) present reversibly distinguishable color change (i.e., from orange red to yellow (or tan) for polymers p-RuLn and from purple to blue for polymers p-FeLn), strongly suggesting that the electrochromic colors could be tuned with the binding metal ion. Interestingly, the electrochromic memory ability and long-term stability (durability) have been found to depend on not only the rigidity but also the length of these triphenylamine-based ligands. It is interpreted that triphenylamine-based ligands with the rigid and short conjugation can promote intramolecular charge transfer from the triphenylamine group (D) to the metallic terpyridine (A), which certainly will effectively stabilize the oxidation state (i.e., Ru3+, Fe3+) of metallic terpyridine and remarkably enhance the memory ability and durability of electrochromic film.